Central American and Panamanian Cycads in Field and Greenhouse
zamias, ceratozamias and dioons
Cycads are a very old and varied gymnosperm division that are quite popular with tropical gardeners and collectors of offbeat plants. Although these attractive cone-bearing plants are relatively rare contemporary inhabitants of subtropical and tropical ecosystems, they were very common elements of global floras a couple hundred million years or so ago during the late Triassic and early Jurassic. Because of this, cycads are often popularized as “living fossils”, a catchy but self-contradictory term also used for some conifers and the more familiar Ginkgo tree (Ginkgo biloba). The order Cycadales includes three extant families, the Cycadaceae, Zamiaceae and Stangeriaceae. Their present distribution is still vast; from southern, central and west Africa, Madagascar, southern and eastern Asia, northern and eastern Australia, New Guinea, several other Pacific islands, to milder climate zones throughout the Americas.
Central America and Panamá have a fairly diverse cycad flora comprised of 35 accepted species vouchered for the region, or approximately 10 percent of all extant described cycad species. This number includes several popular and widely-cultivated landscape plants, such as Dioon mejiae and Zamia neurophyllidia, as well as other far more delicate and “collectible” rare taxa for the specialist such as Ceratozamia hondurensis, Z. manicata and Z. pseudoparasitica.
Many Mesoamerican cycads are arborescent. Some can attain impressive heights after hundreds of years and they can also develop eccentric trunk shapes over time. Worth mentioning are Dioon mejiae and D. spinulosum (shown below), both of which are known to reach ~40’/12.50 m and, together with the northeastern Australian Lepidozamia hopei, are the tallest members of the Cycadales.
Among the many zamias occurring in the Caribbean coastal rainforests of Costa Rica and Panamá, of particular value to ornamental horticulture are a half-dozen magnificent, grooved or plicate-leafed species, some of which were formerly segregated in the (plant) genus Aulacophyllum. From northwest to southeast occurence these are; Zamia neurophyllidia, Z. skinneri, Z. nesophila, Z. hammanii, Z. imperialis and Z. dressleri. This very interesting section for cycad researchers and collectors continues east and southward onto the Pacific versant of Colombia and Ecuador where it is represented by Z. amplifolia, Z. roezlii, Z. gentryi, Z. oligodonta, Z. montana and Z. wallisii. Until fairly recently (Taylor, et. al. 2008) several of the largest Panamanian species were considered localized variants of Z. skinneri and Z. neurophyllida.
Two northwestern South American plicate-leaf cycads. Left, young, potted Ecuadoran Zamia gentryi flushing in the author’s collection in Guatemala. Right, reddish-brown newly-emergent leaves of the Colombian giant coastal native, Zamia roezlii, in the ground in a private collection in Guatemala.
For its size, Panamá is the most cycad species diverse country in the world, with at least 17 accepted Zamia species occurring in ~30,000 sq. miles/77,400 sq. km total territory. Neighboring Colombia is, after Australia, México and South Africa, the fourth most cycad species diverse country overall, with 22 described species in ~441,000 sq. miles/1.14 million sq. km. It is likely that one or more unreported Zamia species presently considered to be Colombian endemics also occur just over the border into Panamá’s lightly-botanized Darién province. Both countries are also known or reported to harbor additional, undescribed cycad species not yet in general cultivation.
Like most cycads, the Central American and Panamanian species are usually large plants at maturity. At least one species has erect leaves of over 12’ /3.70 m long both in nature and cultivation, and several species develop 10’/3.10 m arching leaves. While many are suitable as pot plants for years, as they reach their mature dimensions, they tend to require open space in either a greenhouse planting or a lowland tropical garden to achieve their potential. Larger specimens of the spreading forms can span 15’/4.60 m. Nonetheless, several species perform exceptionally well as pot plants throughout their lives, especially Zamia cunaria, Z. nana, Z. obliqua and Z. prasina. Because of its unique epiphytic and pendent habit, the coveted Z. pseudoparasitica is usually grown as a large hanging basket plant in collections. A number of Mesoamerican cycads have been trialed outdoors in southern Florida and coastal southern California where some have performed well in the landscape.
In an apparent contradiction, anyone familiar with Central American and Mexican cycads in the field is aware that they are now both understudied and over-described depending on the region, the genus and the author. Mesoamerican botanical authorities Michael Grayum and Barry Hammel, writing in 2011 in the Manual de Plantas de Costa Rica’s “Cutting Edge” wryly pointed out, “We've noticed in passing that folks who work on cycads tend to predicate sp. determinations on the minutest of differences between individual specimens.” While some cycad taxonomists may take issue with this statement, I agree that there are certainly instances of this happening in the past. This issue aside, I also believe that most recently-described species appear to be valid and there are many quite distinct regional forms that are either slam-dunk obvious novel species, or warrant disciplined scrutiny.
One of the challenges to evaluating the diversity and intraspecific variation of regional cycads is that relatively few people are familiar with a representative selection of Mesoamerican cycads in the field. Fewer still have seen most of the southern Mexican, Central American and Panamanian species in nature, and less than a handful have seen anything close to all the described, and known but currently undescribed, taxa in the wild. As far as I am aware no-one has seen them all, either living or in herbaria, since some undescribed taxa have not yet made it to a plant press. Note that cultivated plants can sometimes assume leaflet forms and colors, as well as peduncular lengths and cone sizes, that differ from wild plants. While Oaxacan, Chiapan, Belizean, some Costa Rican and many Panamanian cycad localities have been well-visited by botanists and cycad collectors, the majority of Guatemalan, Honduran and Nicaraguan cycad habitats and populations have not.
Another problem with piecing together the regional cycad puzzle is that some species, particularly ceratozamias in northern Nuclear Central America, can be numerically rare and very localized microendemics that are quite easy to overlook when they occur far from roads. Some formerly widespread taxa now have fragmented, distantly isolated populations located at varying elevations that may be tempting to try and differentiate based on minor morphological characters that may represent normal variation between demes within a taxon. As more local or regionally-based botanists became interested in cycads over the past three decades (particularly the last one), our knowledge of their diversity and distribution has increased enormously.
In suitable undisturbed or lightly-disturbed habitats, several regional cycads can be both abundant and quite conspicuous elements of local floras and form colonies into the hundreds or thousands of individual plants. While some formerly robust populations in Panamá have been decimated in recent decades due to development (e.g. Zamia nesophila, Z. dressleri), others remain common and reasonably easy to find in nature. Since 2007, I have found the following species to be relatively abundant still at a few specific sites: Zamia tuerckheimii, Z. stevensonii, Z. neurophyllidia and Z. variegata. Comments made by friends and acquaintances who have recently visited other localities in Mesoamerica indicate that Dioon mejiae, Z. fairchildiana and Z. cunaria are also still extremely common at some sites.
Off their home grounds, some Neotropical cycads can often be difficult to identify with certainty in the absence of developed cones. While leaflet shape, size and marginal teeth arrangement, petiole armature and caudex height and diameter are often used as key characters to typify new regional cycads (especially zamias), in my experience all of these can be very variable within populations. Molecular work has helped to clarify relationships within genera, but this tool is usually unavailable in practical terms to the everyman. Differences between even well-recognized species can often be subtle and challenging to interpret without the entirety of inputs that careful observation of reproductive wild populations provides.
It is common knowledge among U.S. and Central American-based cycad researchers as well as some hard-core enthusiasts elsewhere that there are a significant number of undescribed cycad species reported or suspected from southern México, Guatemala, Honduras, Costa Rica and Panamá. For those unfamiliar with the breed, cycad collectors can be, to put it mildly, “competitive”. In order to sidestep controversy with these populations, as well as threats posed by unregulated extraction that publicizing specifics about them on the internet would certainly prompt, aside from background references they will not be discussed nor shown here.
Likewise, no specific locality data is provided in this article since my past experience has shown that doing so invariably translates into renewed collecting pressure on wild populations by nurserymen looking to add new species and localities to their inventories.
Abbreviations used in the text, TMF = Tropical Moist Forest, TWF = Tropical Wet Forest, TRF = Tropical Rain Forest and TPF = Tropical Pluvial Forest.
Species accounts, in alphabetical order:
Ceratozamia hondurensis – a very localized large and endangered species native to northwestern Honduras TRF. Based on its current highly fragmented distribution and regional deforestation patterns, it probably also occurred in northeastern Guatemala during the last century where it would now have been extirpated. It has a barely emergent caudex in mature plants with leaves to ~9’/2.80 m tall and very wide, thin-textured leaflets. Earlier confused with Zamia tuerckheimii by at least two botanists and cycad collectors, and was cultivated as a zamia in Australia for some time prior to its description in 2008. Subject to special protections in Honduras and, like all species of Ceratozamia, is listed on Appendix I of the Convention on International trade in Endangered Species (CITES). Still quite rare in cultivation but artificially-propagated plants have been produced by private collectors and at least one public garden in the U.S.
Mature leaves on large adult Ceratozamia hondurensis in nature, showing their very wide, membranaceous and somewhat translucent leaflets. Images: F. Muller.
Ceratozamia matudae – a primarily an eastern Sierra Madre de Chiapas, México highland native, it does occur locally in western Guatemalan cloud forest near the border. Previously confused with C. mexicana by some botanists (Standley and Steyermark 1958, Velíz 2008). It has very finely pinnate leaves with decumbent female cones. Cool temperature tolerant and cultivated outdoors in coastal central California, but still rare in cultivation and not considered a particularly desirable species by growers that I know.
Ceratozamia robusta (Costilla de león) – a well-known and somewhat variable species reported from several southeastern Mexican states. The true species is apparently restricted to Chiapas and Tabasco, México, central and northern Guatemala and southern Belize. Central Guatemalan plants can have especially massive trunks with age, to >6’/1.90 m. Mexican and Belizean ecotypes are very popular with cycad collectors, particularly those located in south Florida and southern California.
Wild male cone of Ceratozamia robusta, TWF in central Guatemala. Image: F. Muller.
Dioon mejiae (Tiusinte) – restricted to north central Honduras in mixed Caribbean pine-tropical broadleaf forest. Still abundant at some localities despite reports as recently as the early 1990s that it was threatened with extinction, although it has been extirpated at some sites (Haynes and Bonta 2007). Probably one of the most abundant Central American cycads and certainly the tallest. The large seeds of this species are very popular for the elaboration of special tortillas, tamales and toys throughout their range in Honduras (Bonta, et. al. 2006). A deservedly popular landscape cycad in subtropical and tropical climates around the world. Despite claims made in Jones (1993) and Whitelock (2002) this species is not known to occur in Nicaragua as a wild plant. However, in both that country and Guatemala, they are popular garden plants under lowland tropical conditions and limited regional trade in trunking wild plants probably still occurs. The almost certain absence of Dioon species from Guatemala today remains a mystery to cycad researchers. As currently understood, approximately 450 miles/700 km separate D. mejiae from the closest population in southeastern Mexico, although plenty of ostensibly suitable, rugged Dioon habitat occurs in western and central Guatemala. Dioon merolae is known as far east as western Chiapas on both the Pacific versant and in the Central Depression at low to middle elevations. Given the edibility and documented human exploitation of the seeds of species in this complex and the very dense human population that political Guatemala had during the pre-contact era, perhaps the most reasonable supposition is that the “missing” indigenous member of this genus was simply overharvested as a famine food to extinction or near extinction; relic populations may have been finished off during the second wave of wholesale habitat transformation that began in the 1950s and 1960s in the country. Reports of indigenous dioons from Guatemala, or populations located adjacent to its borders, have thus far been proven to be in error.
Left, a young Dioon mejiae planted in the landscape of a private garden in Guatemala. Right, backlit canopy of a mature potted example of D. spinulosum growing at Golden Gate Orchids, San Francisco, California.
Zamia acuminata – as currently circumscribed, restricted to low and middle elevation wet forests on the Pacific versant of central Costa Rica. Distinguished from the near sympatric Z. fairchildiana by its subterranean or very short emergent caudex to (16”/40 cm versus >6’/1.90 m tall), much shorter mature leaves and the microsporangia arrangement on the compact cones. In limited cultivation in the U.S., Australia and probably elsewhere.
Zamia cunaria – occurring in coastal TRF on the Caribbean in central and eastern Panamá. This species has a subterranean caudex, usually with a solitary leaf in nature, but will hold several leaves in cultivation. It can be locally abundant and may persist in degraded habitats such as pineapple plantings at high population densities (M. Calonje, pers. comm. with image). A handsome, if somewhat understated, pot plant for the space-challenged. Wild-collected seed continues to appear on the international market on an annual basis and is relatively inexpensive, so it is now probably in private collections worldwide.
Zamia decumbens (Corn palm) - from southwestern Belize and probably eastern Guatemala. The famous “sinkhole cycad” from the Maya Mountains that was previously confused with Z. prasina (Whitelock 2002) and Z. tuerckheimii (Standley and Steyermark 1958). Lithophytic on karst at low elevations in TWF. This taxon shares many characters with those in some populations of Z. tuerckheimii that occur at similar elevations further to the west, differing mainly in the length of male peduncles and details of their microsporophylls. It may warrant additional scrutiny with an eye to revising to subspecific status of Z. tuerckheimii. Known populations of both taxa are separated by ~30 mi/48 km airline distance (not evident in the map provided by Calonje, et. al. 2009), both are karst-associated, and there are no obvious phytogeographic barriers to impede gene flow. This species is in limited cultivation and has been for some time, apparently mostly in southern Florida.
Zamia dressleri – central Panamá on the Caribbean versant and just over the Continental Divide on heavy soils in low to very low elevation TRF. A very striking large-leaf zamia with plicate leaflets and an elongated subterranean caudex. Anecdotal reports indicate that it was once locally abundant at a couple of easily accessible localities near the coast. Due to widespread extraction and export of mature plants by foreign collectors in the 1990s and 2000s (almost all of which have probably died), as well as habitat transformation, Z. dressleri is now typically encountered as discrete pockets of immature or young mature plants in nature. Generally found with a single or pair of leaves when young holding two to four pairs of large, plicate pinnae, with older mature plants holding up to three 6’/1.85 m leaves with five to six pairs of very large pinnae. New flushes are a handsome mahogany or orange-brown color. While highly-prized because of its very striking mature leaves, it is not an easy plant for most people to succeed with. Many experienced cycad growers have found them challenging as pot plants in cultivation. My experience is that they require excellent drainage and year-round warmth to thrive, even overnight, and don’t break any speed records on the way from seed to maturity. Supplemental chelated iron drenches every few months seems a useful tweak to improve color and vigor.
Left, a year-old, artificially-propagated domestic source seedling Zamia dressleri in the author’s California collection. Right, mature Z. dressleri at a friend’s greenhouse, author’s Guatemala collection.
Zamia elegantissima – this species has a fragmented distribution at low elevations in central Panamanian TRF on the Caribbean versant. When mature it usually has a noticeably thick trunk and is exceptionally to >9’/3 m tall. Some acaulescent plants I have seen growing in rocky soils on the northern coast of Panamá had developed massive caudexes and very large leaves. In limited cultivation. Requires fully tropical conditions to thrive.
Zamia fairchildiana (Palmito) - is a highly variable “catch-all” and rather vexing Tico zamia that, despite informed opinions to the contrary, may indeed involve several distinct taxa. To confuse the issue even more, the holotype of Z. fairchildiana “has disappeared” from the Costa Rican national herbarium and a sterile lectotype has been designated in its stead (Gómez 2009). As currently defined it is a large, trunking plant with prickly petioles and high leaflet numbers when mature, and is widespread throughout the lowlands and foothill forests of southwestern Costa Rica and into the uplands of western Panamá. It is occasionally littoral and can be subject to saltwater spray on the Osa Peninsula (Calonje 2006). Given its ease of accession, generic Z. “fairchildiana” from throughout the lowlands of southwestern Costa Rica are widely-cultivated and represented in public gardens and private tropical collections around the world.
Left, newly-emerged leaf of Zamia cf. fairchildiana. Right, trunking Z. cf. fairchildiana in middle elevation cloud forest in southwestern Costa Rica. Images: F. Muller.
Zamia gomeziana – is a localized southeastern Costa Rican endemic from middle elevation cloud forest on the Caribbean versant of the Cordillera de Talamanca. Despite some reservations being expressed as to its validity (Grayum and Hammel 2011), its outlier distribution and morphology suggests further evaluation is warranted.
Zamia hamannii – is a microendemic and littoral/coastal species from along the length of the Valiente Peninsula and adjacent offshore islets in western Panamá, where it can occur in areas occasionally submerged in sea water. Despite it’s imposing mature size this, together with Z. skinneri, are among my favorite cycads, and I grow quite a few from two separate sites. Unlike many Z. imperialis, all the Z. hamannii that I have seen reliably have nice new leaf colors, ranging from brassy-yellow to pale orange and peach. I have found this species to be slower-growing than Z. imperialis and seems to require warm nights and warmer days to thrive. Popular with collectors and now available from artificially-propagated material in Australia, southeast Asia and the U.S. Wild-collected seed is still marketed on a more or less annual basis, but artificially-propagated material has recently begun to make its way into horticulture.
Zamia herrerae (Camotillo) - Pacific coastal and foothill forests from Chiapas, México to northwestern Nicaragua. Locally common in seasonally dry habitats of eastern Guatemala and elsewhere in its range. Subterranean with few leaves in nature, but short emergent with full canopy of rather plumose leaves in cultivation. Formerly identified as Z. loddigesii, a similar-looking southeastern Mexican species from the Gulf versant. Not widely-grown outside of Guatemala and El Salvador due to a lack of seed-grown material and unremarkable appearance, but in my experience it is very suitable as pot plant and as a tall ground cover when mass planted.
Zamia imperialis (Cebolla) - localized in central Panamanian TRF. Formerly well-known and commonly traded as Z. skinneri “red emergent”. There appear to be two somewhat distinct ecotypes, the eastern one that occurs on both slopes along the Continental Divide to ~2,300’/700 m with large leaflets, trunks to ~3’/1 m and garnet, orange or copper-brown new leaf flushes. The western form is found at lower elevations to near sea level in Caribbean versant TRF, with mature trunks to >5’/1.50 m, giant leaves and leaflets and light brown or bronze-colored newly-emerged leaves. Plants in cultivation seem to maintain this size differential and variant leaf flush color. I have only found one of the truly “red emergent” plants flushing garnet-colored leaflets in the wild, but I do grow about a dozen plants of this population in California (but not as nice!). In nature, this species usually carries few leaves (three to five) when compared to its close relatives in western Panamá, all of which can retain full canopies with many leaves. This is a very popular giant Zamia species in cultivation and is now artificially-propagated in collections in tropical areas around the world. Surprisingly large examples can be grown successfully in relatively small pots, but their canopies would take up most of the space in many modern living rooms. Wild-collected seed is still marketed from time to time but, happily, appears to be increasingly displaced by high-quality, captive-bred material.
The world can be a small place sometimes. Left, my buddy Fred Muller showing off a nice mature leaf of Zamia imperialis in 2018. Right, our mutual friend Juan José Castillo holding a >10’/3.10 m long leaf at the same locality in the Caribbean lowlands of central Panamá more than a decade earlier. Images: F. Muller and the author.
Zamia ipetiensis – mostly indistinct from Z. cunaria (with which it is essentially sympatric) as an eastern Panamá relic TRF on the Caribbean coast and adjacent secondary vegetation. Subterranean, branched caudex with a solitary leaf to 3’/95 cm carrying few leaflets. This population is said to be noteworthy and distinct due to its leaflet tip shape and the very large number of male cones that larger plants can carry in nature (~12). Sinking this taxon into synonymy with Z. cunaria seems to be a third rail for New World cycad taxonomists, but it certainly seems to be a good candidate for critical review.
Zamia lacandona – mostly an eastern Chiapas, México endemic, reliably reportedly into extreme northwestern Guatemala TMF where it was to be expected in any case due to known populations immediately on the other side of the border. Usually with solitary leaf to about 40”/1 m, occasionally to 6’/1.85 m and known to persist in disturbed habitats. In cultivation but not widely grown due to sparse canopy.
Zamia lindleyi – a large trunking, extremely handsome cycad that is localized at middle elevations in steeply inclined cloud forests of western Panamá. It is somewhat spottily-distributed in nature under dense canopy (photo shown in Whitelock 2002 is atypical), and still very rare in cultivation in Thailand (?), Australia and the U.S. Reportedly challenging to grow in captivity over the long-term and may be temperature and water quality sensitive due to its origin. The entirety of its native range is within a protected area. Formerly identified as Z. chigua “Panamá” and may occasionally still be erroneously considered as such by some regional botanists (Acuña 2010).
Two coning-sized examples of Zamia lindleyi growing in the understory of in climax cloud forest, western Panamá. Images: F. Muller.
Zamia manicata – an unusual but showy species ranging from extreme eastern Panamá discontinuously into western Colombian TRF and TPF. A very interesting dwarf to medium-sized zamia, one of the very few with distinct collared petiolules. Mostly single-leafed in youth but can produce rather long leaves and hold several leaves in nature and cultivation. Despite reports of recent imports of wild seed, this species remains rare in cultivation in the U.S due to apparent difficulties in raising seedlings past eophyll stage. Fairchild Tropical Botanic Garden in Coral Gables, Florida has successfully propagated and distributed this species in the past (Whitelock 2002).
Zamia meermanii – a lithophytic species, usually perched fully-exposed on karst outcrops and their forested bases in TMF in central Belize. It was described a decade ago (Calonje 2009). An interesting plant, apparently narrowly endemic although somewhat reminiscent of the southeast Mexican Z. furfuracea and the sympatric Z. prasina. Short emergent caudex holding a few tomentose leaves that show distinctly nerved leaflets. Still uncommon in cultivation, although recent seedling releases by private growers in the U.S. have helped to promote awareness of this handsome, smallish cycad. Together with other cliff dwelling Mesoamerican cycads such as the southeast Mexican Z. cremnophila, this may prove a welcome and unusual addition to a vertical tropical garden/planted wall.
Above images show Zamia meermanii growing fully exposed on sparsely-vegetated karst outcrops in Belize. Images: F. Muller.
Zamia monticola – under this questionable identity, a plant claimed to be Z. monticola occurs in scattered populations in in premontane TWF in central Guatemala. While prevailing opinion among the cycad-wallahs places Guatemalan plants within this rather enigmatic taxon and has done so for more than 60 years (Standley and Steyermark 1958), the uncertain origins of the holotype and the lack of a female type specimen suggest to me that Z. monticola should be applied only to clonally-propagated plants traced to the original Chamberlain accession from Veracruz, México. For a variety of reasons, the Guatemalan material should be described as a new species. Calonje, et. al. (2009) guardedly refer to the uncertain taxonomic status of Guatemalan plants when comparing Z. monticola to Z. decumbens in that species’ description. At some localities this taxon occurs in sympatry with Z. tuerckheimii. Despite the superficial similarity and shared habitat with Z. tuerckheimii, it now appears that this species’ affinities may lie closer to Z. onan-reyesi, Z. fairchildiana and Z. gomeziana. Short-trunking, upright or leaning. As is shown here, its petioles are heavily armed with stout spines. Leaflets may or may not be strongly falcate depending on the individual leaf or the leaf’s position on the plant and/or prevailing light conditions. Very small numbers of plants are in cultivation in Guatemala, where both sexes have now coned.
Left, female cone and short-emergent caudex of z cultivated Zamia cf. monticola showing the very prickly/aculeate petioles that are characteristic of this taxon. Right, leaflet detail of Z. cf. monticola. Images: J.J. Castillo and F. Muller.
Zamia nana – is an extremely localized dwarf cycad in central Panamanian low elevation cloud forest with a subterranean caudex and a fairly compact canopy. While often overlooked by cycad collectors due to its admittedly rather unremarkable appearance, this can be a great pot plant for growers with limited warm-growing space. It holds few leaves as a young plant but can grow a nice, full canopy as a large adult. Despite the ease with which some populations can be seen in nature, this species is rather vulnerable due to a very restricted range and continued poaching pressure on larger plants by visitors. Older plants are now definitely less common at known sites than they were about a decade ago.
Zamia nesophila – another localized, insular and often littoral species in western Panamá that was reportedly formerly abundant to the tens of thousands at the type locality. Big to giant, green-emergent and very salt tolerant. This is the tallest of the Panamanian groove-leaf zamias with trunks to 10’/3.10 m. It apparently performs well in the landscape in south Florida, showing some promise as garden plant and tolerating more direct sun than its close relatives from western Panamá. Fairly easy to obtain in the U.S. from both wild-collected and artificially-propagated seed.
Zamia neurophyllidia – is widespread from coastal and low elevation TRF in southeastern Nicaragua, Costa Rica and western Panamá. Occasionally littoral or occuring in low-lying swamp forest. While often thought of as a short-trunking plant, observations in Costa Rica and extreme western Panamá have shown that it can grow to at least 8.5’/2.70 m tall (Calonje 2006). Probably the best-suited and easiest to obtain pot plant among the groove-leaf zamias and seemingly popular with generalist palm and cycad growers around the world. An excellent addition to shady spots in warm tropical gardens anywhere. Now readily available from wild-collected and artificially-propagated seed. Like many Panamanian and Costa Rican plicate-leaf zamias, wild plants are almost invariably nicer-looking than cultivated examples.
Zamia obliqua – discontinuously from central and eastern Panamá on both versants into western Colombia. The southwestern Costa Rican record very likely in error and is probably an aberrant juvenile Z. fairchildiana (Lindstrom, et. al. 2013). Central Panamanian populations and Darien and Chocoan Colombian plants may represent distinct taxa (Taylor, et. al. 2012), with Canal Zone Panamanian plants being generally smaller overall. Zamia obliqua can reach 16’/5 m with correspondingly wide canopies in the lowland pluvial forests of western Colombia (Benavides, et. al. 2010). A beautiful species for tropical garden, conservatory or warm greenhouse that reportedly handles pot culture well.
Zamia onan-reyesii – briefly recognized under its synonym, Z. bussellii (Schutzman, et. al 2008). This is a somewhat localized arborescent species in foothill and intermediate TWF in northwestern Honduras. Large, usually with erect trunks with a full canopy and lightly-spined petioles. Its large seed and eophyll morphology put this plant closer to Z. fairchildiana and related species than to the proximate Z. tuerckheimii and Z. decumbens. An isolated population of handsome, short-trunking terrestrial zamias discovered by the author growing on soil in foothill TWF in eastern Guatemala in the late 1980s may represent a disjunct population of this species. Zamia tuerckheimii populations that occur in the same general ecoregion are restricted to karst outcrops. Two duplicate slides of these plants were provided to Jody Haynes, then the Cycad Biologist at the Montgomery Botanical Center in Coral Gables, about 15 years ago; sadly, this site has since been overrun by squatters. Curiously, there are quite a number of “outlier” plant and animal species reported from northwestern Honduras and extreme eastern Guatemala whose closest relatives are located south of the Nicaraguan Depression in the uplands of southern Costa Rica. As pictures here show, this can be a very beautiful cycad when found in heavily-shaded, lightly-disturbed forests. Leaflets somewhat papery in texture.
Zamia oreillyi – a very localized species in north-central Honduras TRF. Differs from the closely-related Z. standleyi by higher leaflet numbers whose edges are overlapping. This species has very handsome new leaf flushes but holds only one to three in nature and probably one or two more in cultivation. Not widely cultivated, probably due to a scarcity of planting material, but probably a very good candidate for pot culture.
Zamia prasina (Camotillo) - widespread in Chiapas and on the Yucatan Peninsula in México, also in Belize and northern Guatemala with very localized populations with long leaflets in eastern Guatemala. Formerly known as Z. polymorpha and confused with Z. loddigesii and Z. decumbens by others (Standley and Steyermark 1958,; Whitelock 2002). There are several leaflet forms of this plant from across coastal, savannah and TMF ecostems throughout its range. It can be ubiquitous in seasonally dry low forests throughout much of the Yucatán Peninsula. Its extreme variability of form and size appears to have tempted at least a couple cycad taxonomists into proposing splitting it into at least two species.
Zamia pseudomonticola – a doubtfully distinct close relative (?) of Z. fairchildiana; as accepted a cloud forest southwestern Costa Rican and western Panamanian species. The description indicates a tall species with smooth petioles and relatively short peduncles. The plant reportedly has a fairly upright trunk when mature. The inability of subsequent searches to encounter plants that match the description at the type locality raises reasonable questions as to its validity and suggests that it is conspecific with Z. fairchildiana (Whitelock 2002; Calonje 2006).
Zamia pseudoparasitica – lowland TRF and low cloud forests in central and western Panama along the lower parts of the Continental Divide and Caribbean versant to about 3,600’/1,100 m elevation. Mature plants have long, curved caudexes to ~3’/95 cm in length, with leaves exceptionally to over 10’/3.10 m in length. While usually photographed in the upper canopy, plants may occur on relatively small trees and surprisingly small branches in very shady undercanopy. Despite reports to the contrary, occasionally fallen plants can re-root, flush new leaves and persist alive for considerable time on the ground if fortunate enough to settle on a well-drained slope (pers. obs. – see image here). Rarely lithophytic and littoral on the Caribbean coast (fide W. Lamar). Because of its epiphytic growth habit and handsome aspect, this is a very popular cycad species for display with both public gardens and private growers. I have successfully grown Z. pseudoparasitica in both plastic and wooden baskets and have recently found it surprisingly fast-growing from artificially-propagated seed.
Zamia sandovalii – a lithophyte in riparian TRF habitat localized in north central Honduras. It holds few leaves in nature and is reportedly in somewhat limited cultivation, although it has been artificially propagated in Florida, Australia and Thailand. Thus far, this species does not appear to be very compelling to growers outside of botanical gardens and some specialist collections because of the few leaves it holds. The image suggests that it might be a more promising species in cultivation as a hanging plant than its current lack of popularity indicates.
Zamia skinneri – this species is currently considered to be of localized distribution at low elevations and foothill TRF in western Panamá but may range into forested parts of extreme southeastern Costa Rica. It displays beautiful emerald green leaf flushes, with the leaflet pair number on mature plants usually five or six. An exceptionally fine species for ornamental horticulture and very suitable for long-term pot cultivation for growers with a bit of shady warm space. While normally short-emergent, some quite tall trunking plants have been photographed in nature (Taylor, et. al. 2008). True Z. skinneri appears to be relatively uncommon in nature and even more rare in cultivation, but it is worth seeking out for the very beautiful new leaf flush colors alone.
Zamia standleyi – native to northwestern Honduras in TMF and into extreme eastern Guatemala in TWF. May also be commonly found in drier habitats inland and further to the east in Honduras. Usually holds a solitary or pair of leaves in nature but may hold a higher number in cultivation. Leaflet numbers, shape and width in adults vary depending on origin. Rusty-brown or mahogany-colored new leaf flushes. Intergrades with Z. variegata in low elevation TRF on the Guatemalan-Honduran border, where plants exhibiting Z. standleyi leaf and leaflet morphology sometimes display cream-colored or light-yellow leaflet spotting.
Zamia stevensonii – localized in TRF and low cloud forests in central Panama. While called “blanco” in the rare plant trade due to many (most?) plants flushing new leaves white, I have observed that not all individuals in upland populations exhibit this trait. Commonly arborescent to 4’/1.25 m, occasionally a bit taller, with a thin trunk to an observed maximum of ~4”/10 cm wide. Its very close relative, Z. elegantissima, generally has a “beefier” look in nature, with thicker, taller trunks and longer leaves. To at least 2,600’/800 m in low elevation TRF and cloud forest in central Panama. At least one population was systematically poached of large trunking specimens in the late 2000s, but as of the fall of 2018 appears to be recovering from a remnant group of younger plants left behind.
Zamia tuerckheimii – traditionally considered to be endemic to northern and central Guatemala, usually in lowland TWF, but highly likely to range just into extreme eastern Chiapas, México due to proximity of some Guatemalan populations to the border. A large to very large, usually lithophytic and often cliff-dwelling zamia that is well known, but under-represented in cultivation. An exceptional plant for fully tropical landscapes and, as is shown here, is very dramatic-looking in mass plantings under light shade. Not a great selection for areas where it will be exposed to bright afternoon sunshine where it will burn. It grows acceptably well but does not look its best in cooler tropical climates, where it will be slow. Suitable as a pot plants in well-lit interior settings for many years but watch for mealybug infestations. Trunks in nature are often decumbent, “U”, “S”-shaped or corkscrewed and may exceed 9’/2.75 m in length at some undisturbed sites. Locally abundant (still), with limited extraction of large plants occurring at some easily accessible sites for the local garden market. The disjunct southern and upland population, discovered by Jonathan Campbell during herpetological fieldwork in the early 1980s, differs from better known ecotypes in being somewhat larger overall at maturity, consistently exhibiting a higher leaflet number in older plants and in having two pairs of leaflets versus one on their eophylls. Petioles in this species may be smooth, sparsely-spined or moderately-spiny depending on the locality. Leaflet morphology also varies between some populations.
Zamia variegata – extreme eastern Chiapas, Mexico through most of northern Guatemala, Belize and just into northwestern Honduras. Formerly known as Z. muricata var. picta or Z. picta. Mostly restricted to the understory TWF and TRF, but some populations may occur in more open, drier foothill environments together with native Caribbean pine (Pinus caribaea). This species can be confusingly variable even within small populations, probably reflecting the morphological influence of three other sympatric zamias that it apparently hybridizes with; Z. standleyi, Z. prasina and a currently undescribed central Guatemalan species. Plants in eastern Guatemala occasionally to at least 12’/3.70 m tall with a very short emergent, stout caudex to >10”/25 cm in diameter. Usually subterranean until extremely old, when it can be short emergent on karst or serpentine. Its canopy is upright, often of shuttlecock habit when grown under bright conditions, but may spread in deep shade. Lithophytic or terrestrial. Leaflet color ranges from pure green to almost entirely yellow, with the brightest flash markings evident on coastal plants. Color extremes may be found side by side in mature plants in at least one population in Guatemala. Frequently littoral in Caribbean Guatemala where it may occasionally be subject to flooding with brackish water. Except for some putative Z. standleyi hybrids on the Honduran-Guatemalan border, plants appear to decline noticeably in height from east to west. Although Calonje, et. al. (2009) report that this species is restricted to elevations below 975’/300 m in Belize, I have seen and included here a photograph of this species in premontane TRF along the Guatemalan-Honduran border at ~2,275’/700 m
Two manmade hybrids involving Z. furfuracea retained the yellow leaf spotting of the Z. variegata seed parent (Whitelock 2002).
Left, a leaf of an apparent intergrade between Zamia variegata and an undescribed Guatemalan Zamia sp. in nature in central Guatemala. Right, a typical pennant-type, chartaceous leaflet of a plant from eastern Guatemala. Images: F. Muller and the author.
Central American and Panamanian cycads in cultivation
Unsurprisingly, some regional cycads are very easy to grow, others aren’t. The wide variety of soils and environments that Central American and Panamanian cycads have adapted to makes it difficult to generalize as to recommended soil types other than to focus on the uniform need for excellent drainage and the incorporation of some moisture retentive components. Despite some species originating from heavy clay soils or swampy conditions, tropical zamias despise having their caudexes and roots waterlogged in cultivation for any length of time. Ironically, some of the most notoriously difficult to cultivate neotropical zamias (e.g. Zamia amplifolia, Z. manicata) come from the most saturated soils in nature.
Because many of the species discussed here attain large sizes when mature, most major collections of Central American and Panamanian cycads are located in tropical and very warm subtropical areas where they can be grown outdoors year-round. The epicenter for these collections is centered in south Florida, which has two major botanical gardens housing collections of regional cycads (Fairchild and Montgomery) and many private collections and nurseries that work with rare Neotropical cycads. Other U.S. collections of note are in Hawaii and coastal southern California, where one botanical garden (Huntington) has an extremely good collection of regional cycads. Some cycad growers in northeastern Australia have species diversity on their properties that probably rival most U.S. collections that specialize in this group. There are also a few very well-known Central American and Panamanian cycad collections in Thailand, South Africa and France, as well as two very comprehensive collections of regional cycads in Guatemala.
Generally speaking, Central American and Panamanian cycads grow best under light to medium shade, that can be from tree canopy, whitewashed polycarbonate or knitted polyethylene. Most benefit from constant warmth, good water quality and high humidity. All of the upland species are tolerant of cooler temperatures than they normally experience in nature, and a few cloud forest species may require greatly reduced night temperatures to survive long-term.
Pot plants: all growing media should be very free-draining, with at least 50% of volume comprised of pumice (preferred) or medium-grade perlite. Fine conifer bark together with equal amounts of well-composted forest products should make up the rest. Amend with time release fertilizers and dolomitic limestone as needed. Mineralized tap water will leave unsightly halos on leaflets and may burn the roots and leaf tips of some delicate zamias, so growers may want to experiment with RO-source or distilled water for zamia species that aren’t thriving in pots. Some lowland rainforest species appear to require uniformly warm temperatures throughout day and night to thrive, especially Z. manicata, Z. hamannii and Z. dressleri. Zamia pseudoparasitica requires a slightly different mix for basket culture than that used for lithophytic and terrestrial cycads. I use fine and medium conifer bark together with equal parts of horticultural charcoal and coarse perlite, and with a small amount of New Zealand sphagnum moss blended in to tie the mix together.
Compots of artificially-propagated F1 seedling regional zamias surface-sown on pure pumice. Left, line-bred 18 month-old Zamia variegata; right, seven month-old Z. hamannii.
Almost all of the described regional cycad species are now in cultivation, although a few are still rare in both private collections and public gardens (e.g. Ceratozamia hondurensis, Zamia monticola, Z. sandovalii). Several undescribed species have also entered limited cultivation in Guatemala, the U.S. and Thailand.
In the landscape: some of the larger species discussed here are well-known, high-end tropical landscape subjects, including Ceratozamia robusta, Dioon mejiae and Zamia neurophyllidia. Other species, such as Z. nesophila, Z. variegata and Z. tuerckheimii are also gradually finding their way into mixed tropical plantings as greater numbers of seed-grown plants become available to commercial nurserymen throughout the tropics.
Pests: mealybugs (Pseudococcidae) are a frequent headache in many cycad collections but, where legal, can be eradicated or controlled by periodic drenches of imidacloprid and Safari (Dinotefuran) at labelled rates. Sooty mold development on leaflets it a good “tell” that the plant has a mealy infestion. Spot sprays of contact insecticides, particularly new-generation insect growth regulators, are also useful to keep infestations under control.
Armored scales (Diaspididae) can be even more problematic…
Asian cycad scale (Aulacaspis yasumatsui); one of the “unarmored” armored scales, was apparently introduced into the U.S. (Miami, Florida) from southeast Asia in the mid-1990s and has rapidly become a nightmare for some cycad growers around the world. It is also a threat to wild cycads and is currently decimating some populations of insular Pacific Cycas species. Since the latter part of the last decade it is widespread in nurseries and gardens growing Cycas species in Guatemala and (now) in southeastern México where cycad researchers are deservedly concerned that it may spread to native species. Besides Old World cycads, this pest is now also known to infest Dioon merolae, D. spinulosum, D. purpusii, Zamia loddigesi, Z. splendens and a variety of other Neotropical cycad species (Normack, et al. 2017, L. Noblick pers. comm., J. Abascal pers. comm). It appears to require tropical or warm subtropical conditions to thrive. There are no current reports of this pest from Panamá and Costa Rica. Very specific systemic pesticidal and biological control measures of varying efficacy are available to combat cycad scale, with periodic drenches of Safari and imidacloprid being front line defenses. Most contact insecticides and “hippy” solutions like applying spent coffee grounds and neem oil appear to be a waste of time and money. Anecdotal reports suggest that even within genera known to be especially susceptible to cycad scale, some species are far more vulnerable than others and that these should be avoided where this pest is established in the landscape.
Other less-specialized armored scales respond quickly to the treatments discussed above for mealies and cycad scale.
Caterpillars; in tropical landscapes located where zamias and ceratozamias are native, the larvae of Eumaeus butterfly species can be persistent and devastating pests if ignored, attacking new leaves in particular (pers. obs., J. Abascal, pers. comm.). They can be controlled by manual removal if occurring in small numbers or with contact or anti-feedant larvicides. In Guatemala and probably elsewhere, some noctuid moth larvae will also predate newly-emerged cycad leaves, destroying new flushes in minutes.
Slugs; are an occasional pest in both greenhouse and landscape and will damage or kill newly-emerging leaves in a single feeding session. Baiting with beer traps or molluscicides are effective controls. Take preventive steps to avoid contact/exclude if you have pets or wildlife entering growing areas where the latter have been applied. Metaldehyde is DEADLY to dogs; no antidote available, so exercise caution when using it if you have bow-wows around.
Fungal rots and leaflet spotting; periodic drenches of Banrot (etridiazole and thiophante-methyl) are useful when expecting prolonged wet weather and coupled with dithane + mancozeb + surfactant sprays will help prevent caudex rots and leaf spotting. I have made inconclusive trials with both mycorrhizal fungi and bacterial innoculants over the past 15 years, specifically with Actinovate AG (Streptomyces lydicus) in California and commercially available mycorrhizal strains in Guatemala. These applications were made in an attempt to improve vigor of sometimes challenging subterranean rainforest cycad species like Zamia dressleri and the upper Amazonian Z. ulei. They certainly didn’t appear to do any harm, but I’m not sure that I saw any tangible benefits either. Nonetheless, I keep an open mind about use of these products and believe that they can add an extra boost to otherwise healthy plants that seem to be struggling a bit. It may seem obvious, but don’t apply packaged mycorrhizae to your soils if you’ve recently drenched or sprayed a systemic fungicide.
Mice and rats; can be a genuine pain in the ass in cycad collections around the world and will randomly chew or feed on older stems of the less toxic species. They will also gnaw on and steal seeds, clip petioles on seedlings and dig around plant bases. Every grower has their lethal control measure/s of choice, so have at it folks!
I would like to thank my friend and colleague Fred Muller (again) for providing many outstanding photographs of wild cycads and sharing his now unparalleled familiarity of Mesoamerican cycads in the field. There is little doubt that he has now observed and photographed more regional cycad species in nature than anyone else. Chris Hall and Dr. Arden Dearden of Queensland, Australia have very generously shared images taken in their nursery, private collection and in nature, as well as some valuable Panamanian localities, growing tips, and artificially-propagated seed with the author. Twenty years ago, Neil Carrol very kindly provided me with both “go-to” localities and his extremely good insights into Panamanian cycads and aroids in nature that remain valuable to this day. My good friends Ing. Juan José Castillo and Jaime Abascal have generously cared for my Guatemalan cycad collection for the past five years. Greg Holzman, who knows and grows Panamanian zamias as well as anyone, was kind enough to share the amazing image of a new flush on one of his mature Zamia hamannii shown here. Rory Antolak, who is familiar with most Mesoamerican cycads in nature and gardens, also provided informed and welcome background color on the state of rare cycad cultivation in south Florida and elsewhere. He also shared his thoughts on the placement and relationships of some little-known regional species based on his examination of them in the field.
The regional distribution lists of accepted cycad species are as follows:
(*indicates grown in the author’s U.S. collection; +indicates grown in my Guatemalan collection)
Zamia lacandona (reliable report)
Zamia cf. monticola+
Zamia decumbens (highly probable)