The Big Five

Notes on the first group of hydnophytines that made it in the big city


Hydnophytum formicarum, H. moseleyanum, Myrmecodia tuberosa, M. beccarii and M. platytyrea


I must admit that the caudexed ant plants (Rubiaceae, subtribe Hydnophytinae) from Malesia, New Guinea, Fiji and northeastern Australia need a snappy new name. “Ant plant” is too vague a term to circumscribe them, since it encompasses a huge number of unrelated plant groups that also have mutualistic relationships with ants, including many commonly cultivated ornamentals such as orchids, bromeliads, ferns, hoyas and dischidias, etc. For a while I tried to popularize the term “ant rubiac” on web plant fora with a notable lack of success.

“Hydnophytine” is starting to become more popular among specialist ant plant growers but generally elicits a blank stare when used with people outside of the clique.  Nevertheless, since it now appears that some aberrant members of this subfamily are not actually associated with ants, “hydnophytine” is certainly the most precise and currently preferred term. If anyone has a better idea for a popular name for these plants, please let me know.

“Testicle plant” has already been proposed by a local wag here in California, but - while suitably weird - regrettably seems to have little commercial appeal when printed on a plant tag.

Hydnophytines are (finally!!) beginning to attract a wider following among tropical epiphytic plant aficionados and cactus and succulent growers around the world. While they have been in limited cultivation in the west since the late 19th century, when rare plant collectors like Frederick Burbidge and others attempted to take live plants to England from Borneo and elsewhere in the region, they have never had a big following among rare plant collectors. The “Kew Bulletin of Miscellaneous Information” of 1897 notes that the Veitch’s nursery was apparently the first to successfully import a living hydnophytine in 1886 (Myrmecodia beccarii), although attempts to send live plants to England had been made as early as 1860 by the famed naturalist Alfred Russel Wallace. Under the direction of Sir Joseph Hooker and others, the stove house collection at Kew apparently housed several Australasian hydnophytine species by the turn of the century.

Young mature examples of Tropiflora's forms of Mymecodia tuberosa bracteata, M. tuberosa armata and M. beccarii "Hull River' growing mounted on cork tubes in an indoor atrium in Guatemala, 2008.

Modern horticultural interest in hydnophytines seems to be a very recent phenomenon, mostly dating to the late 1980s and early 1990s when several wild-collected accessions trickled into U.S. private and public collections like the Marie Selby Botanical Gardens in Sarasota, Florida. From Selby, a few species were further distributed by other botanical gardens who propagated them on such as the Huntington in Pasadena, California, as well as through commercial sources like Tropiflora, also located in Sarasota. Plants that can be directly traced back to original Selby introductions include Myrmecodia tuberosa "bracteata" ex-Bako NP, Sarawak, Malaysia (#1978-0089), M. beccarii Tully, Queensland, Australia (#1989-0149) and M. (tuberosa) dahlii ex-New Britain, PNG (#1990-1042).

Books such as Gordon Rowley’s “Caudiciform and Pachycaul Succulents” (1987) mention hydnophytines in passing, but generally speaking these plants remained the exclusive province of a few botanists and ecologists working in the Indo Pacific region (e.g. Camilla Huxley and Matthew Jebb) and articles dealing with them were mostly of a taxonomic or animal behavioral nature. The sole exception seems to be Myron Kimnach’s lengthy note on the giant Papuan hydnophytine species, Myrmecodia lamii, published in the Cactus and Succulent Journal (U.S.) in 1996 (Vol. 68).

The first contemporary publication that I have found that deals with this group of plants at a detailed but popular level in horticulture is Nicholas Plummer’s excellent article, also in the Cactus and Succulent Journal (U.S.), “Cultivation of the epiphytic ant-plants, Hydnophytum and Myrmecodia (2000 Vol. 72, No. 3). While it obviously seems dated when read almost two decades after being written, Plummer provides a great deal of valuable information about the origins of the plants then available from U.S. nurseries and showed very good insights about the occasional challenges of growing these plants under his conditions in North Carolina.  

Among other things, Plummer also pointed out the differences between the two widely-distributed Hydnophytum species then available in the trade, as well as taking a stab at identifying some more confusing material then circulating from the genus Myrmecodia. All the less common hydnophytine species he included on his “wish list” in concluding remarks are now in cultivation in the EU and U.S.

The next notable grower to offer recommendations on how to cultivate these plants successfully was Philippe de Vosjoli in his “A Guide to Growing Pachycaul and Caudiciform Plants” (2004), also known as “Pachyforms”. While this book and its sequel in 2007, “Bonsai Succulents – Pachyforms II”, are excellent reference works for newly-minted caudiciform growers, his scant notes on Hydnophytum formicarium (sic) and Myrmecodia tuberosa are of little value to growers today. Mr. de Vosjoli did, however, show foresight in urging nurserymen to work to establish the easily cultivated Queensland native, M. beccarii in permanent cultivation in the U.S, which has since occurred for both the northern ("spiny") and southern ("smooth") populations, as well as the intergrade between the two.

In 2008, Australian succulent grower and photographer Attila Kapitany wrote a very good and well-illustrated article on his native species, yet again in the Cactus and Succulent Journal (Vol. 72, No. 6) titled, “Weird and Wonderful Ant-House Plants”. This article shows all the Australian hydnophytine species growing under natural conditions in northeastern Queensland as well as in cultivation, in addition to the two ant-associated Dischidia species (Apocynaceae) that occur there as well. There is a brief section on these plants in cultivation in Australia and probably the first image published of the rare but increasingly popular FNQ endemic, Hydnophytum ferrugineum. Prior to the epiphytic myrmecophyte forum coming online in 2014, that showcased Derrick Rowe’s and Andreas Wistuba’s beautiful photographs of wild hydnophytines, Kapitany’s images were among the very best available of these plants in nature.

Since hobbyist growers outside of their origin countries were largely restricted to growing five hydnophytine species until about a decade ago, I jokingly refer to these plant pioneers after their African dangerous game “must collect” counterparts, “The Big Five”. While viewed as commonplace by specialists today, most of these (plant) species offer the advantage of being easy to find at reasonable prices in the specialty nursery trade and are straightforward to grow. Two discussed below (Hynophytum moseleyanum and Myrmecodia beccarii), as well as a couple others are currently produced from seed in large numbers for the mass market by Corn.Bak of the Netherlands and sold worldwide through their distributors. All of them also have very distinct ecotypes available at this time, which allows for interested collectors to assemble – say – at least six different forms of H. formicarum (two Philippine ecotypes, Sumatra, Singapore, Bali and Papua New Guinea-PNG) and four M. platytyrea (two Australian subsp., one East Sepik Prov., PNG and one Milne Bay Prov., PNG).

I will briefly deal with all five species here, including experience growing them out of doors year-round under Lexan in Guatemala and greenhoused in California. Frank Omilian and Nicholas Plummer did much of the heavy lifting over the years, learning how to grow them well and to sleuth the origins of some of these plants in cultivation today. For these and other efforts made by them to introduce new species into cultivation they deserve a good measure of gratitude from the hydnophytine grower community.

Two adult, 12 year-old, seed grown and recently-pruned  Hydnophytum formicarum  from Luzon island, the Philippines, growing together in a 12"/30 cm basket and cool greenhoused in California

Two adult, 12 year-old, seed grown and recently-pruned Hydnophytum formicarum from Luzon island, the Philippines, growing together in a 12"/30 cm basket and cool greenhoused in California

Hydnophytum formicarum (incl. “Horne”)

Together with Myrmecodia tuberosa in its broadest traditional sense, the most widely-distributed hydnophytines. Occurring from Peninsular Myanmar and Malaysia, the Philippines and Sulawesi through Borneo and Sumatra, Java and Bali eastwards to the island of New Guinea. Based on photos taken of wild plants and cultivated material in hand, southeastern Thai, Cambodian and Vietnamese plants appear to correspond to H. sp. “Horne”. This is a very large-caudexed species from seasonally dry forests of SE Asia that is morphologically distinct overall and also produces much larger, elongated fruits than true H. formicarum. This taxon will be discussed in a later post.

Hydnophytum formicarum is one of the most common hydnophytines in cultivation, largely due to its ease of cultivation, popularity among collectors and prolific seed production from an early age onward. It is commonplace to find very young plants fruiting and producing viable seed in community pots. Despite its ubiquity, it is a very rewarding plant to grow. There are plants available from several origins in the EU and the US, the most common of which originated in the Philippines and Singapore (where they are locally endangered as wild plants).  Recently, plants from other interesting localities such as the Harau Canyon in West Sumatra have come onto the market. There is definite variability among some of the different populations, particularly with regard to mature caudex size, stem lengths, leaves and caudex morphology.

Six year-old, seed grown Hydnophytum formicarum, propagated from original accession acquired from a plant vendor at the Manila Lung Center Market, Manila, Philippines

Most forms can be grown to mature size in 8”/20 cm pots or baskets. They require excellent light to maintain erect stems with small leaves; shaded conditions produce an unnatural, floppy growth habit that can be partially corrected by pruning. Many ecotypes appear to be cool tolerant, including several that I cultivate. They are also fairly drought tolerant, more so than most members of the family now in cultivation.

I currently grow several forms of H. formicarum, including the following:

Pumpkin”, ex-Quezon Province, Luzon, Philippines. This plant has the most conspicuously ridged caudex of the forms that I grow, and the one with the largest caudex and canopy so far. A very handsome and desirable plant.

Manila Lung Center Market, Philippines. Also traded as "LCM". Similar to “Pumpkin”. Reportedly, it also has a nice-sized caudex when fully mature.

Singapore form. One of the smallest forms in cultivation, generally with a lightly-ridged caudex. Some plants have nice pink and green highlights on their caudexes when young. Very prolific and, because of its size at maturity, the best form for well-lit and ventilated terraria and vivaria.

Bali nursery. A rare form in cultivation, characterized by very small caudexes proportionate to their stem length. Strongly decumbent with age. Originated from material found at an orchid nursery on Bali by a friend.

Harau Canyon. A West Sumatran ecotype that was introduced to cultivation by Andreas Wistuba. My pair of plants are still small. Leaves somewhat wider than other forms that I grow.

Five year-old seed grown  Hydnophytum formicarum,  growing in 6"/15 cm basket and propagated from F1 material originating from a commercial orchid nursery in the Balinese highlands. Note very small caudex in relation to stem length, a characteristic of this ecotype.

Five year-old seed grown Hydnophytum formicarum, growing in 6"/15 cm basket and propagated from F1 material originating from a commercial orchid nursery in the Balinese highlands. Note very small caudex in relation to stem length, a characteristic of this ecotype.

Caudex details of the three forms of Hydnophytum formicarum shown above. From left to right, "Pumpkin", "Manila Market", "Bali Nursery".

There is also a commercially traded form, reputedly from PNG and ex-Tropiflora. It is cultivated in several US public gardens and, presumably, many private collections around the world. This plant has a smooth or sometimes indistinctly-ridged, somewhat globose caudex and may represent a different species. Otherwise, culture the same as above.

Hydnophytum moseleyanum  , Tropiflora #617. Young mature caudex grown outdoors in Guatemala.

Hydnophytum moseleyanum , Tropiflora #617. Young mature caudex grown outdoors in Guatemala.

Hydnophytum moseleyanum (incl. H. “papuanum”)

Flower buds and fruits, Tropiflora's Hydnophytum moseleyanum #617 ex-PNG

Sometimes confused with H. formicarum in the past, but identification keys provided online by Frank Omilian and others have helped to clarify identities of cultivated plants. A very commonly-cultivated hydnophytine as well that rapidly achieves large caudex sizes (>12”/30 cm) under good growing conditions. Very suitable for outdoor cultivation as a hanging plant in suitable climates. Known from central and eastern PNG and islands to the southeast and northeastern Queensland, Australia. It still circulates in horticulture under the synonym H. papuanum. Until recently, almost all material in cultivation was ex-Tropiflora (or Selby?) accessions without exact origin data attached. This is also the case with a dark-caudexed form that originated from the University of California Davis Botanical Conservatory as well as assorted plants purchased by visitors to Thailand and Singapore whose progeny is sometimes offered online. Over the past several years, seed-grown plants with precise locality sources have been grown by Frank Omilian and me from near sea level in both Morobe and Milne Bay Provinces, PNG. Easy and fairly cool tolerant.

Young mature Hydnophytum cf. moseleyanum "Dark Caudex" ex-UC Davis BC

I grow the following forms:

Tropiflora” ex Selby (?). Collected by a “Wallis” in Queensland as H. papuanum. Very vigorous and now in mass production as a specialty houseplant in the EU.

"Tropiflora #617" ex-PNG.Classic form of the species, very fast-growing and an annoyingly prolific fruit producer.

Lae, Morobe Prov., PNG. Still small, but images of mother stock in Queensland collection show nice plant form.

Milne Bay Prov., PNG. As above. Fast-growing, like most forms of this species.

Dark caudex. UC Davis Conservatory, originally accessioned by them as a H. formicarum ex-B. Mostel. ID tentative.

Three year-old seed grown  Myrmecodia tuberosa "bracteata"  growing in a 6"/15 cm basket in a California greenhouse. This is ostensibly a direct descendant of Michael Madison' Sarawak collection accessioned by Selby under #1978-0089, made four decades ago, and that has entered the trade as both HBG #51501 and Tropiflora #3757

Three year-old seed grown Myrmecodia tuberosa "bracteata" growing in a 6"/15 cm basket in a California greenhouse. This is ostensibly a direct descendant of Michael Madison' Sarawak collection accessioned by Selby under #1978-0089, made four decades ago, and that has entered the trade as both HBG #51501 and Tropiflora #3757

Myrmecodia tuberosa (incl. M. “echinata”, M. dahlii, M. tuberosa “armata”, M. tuberosa “bracteata”, M. tuberosa “sibuyanensis”)

This rather unwieldy, polymorphic and widely distributed plant, treated as an ochlospecies by Huxley and Jebb in their monograph (1993) on the genus, has now been split by other taxonomists into a number of distinct individual species currently recognized by The Plant List (Kew-MOBOT). Since all of them are now in cultivation, most will be discussed in later posts. For purposes of this piece, the M. tuberosa originating from mainland SE Asia to Java (“armata”), Sarawak (“bracteata”) and the lowland Philippines (“sibuyanenesis”) are all considered to be part of the same species complex. Most of the PNG and its southeastern insular forms (incl. M. dahlii), material from northeastern Queensland, Australia, etc. are treated as distinct species here.

The first two varieties (subspecies?) mentioned above are the most commonly grown forms of this species. The collection made by Michael Madison of Selby BG in Bako NP, Sarawak in 1978 is now certainly the oldest of the cultivated hydnophytine lines documented in the US.

Caudex detail, young mature Myrmecodia tuberosa "bracteata". This plant is extremely variable-looking depending on cultivation conditions.

Myrmecodia echinata is a commonly seen synonym of M. tuberosa, and cultivated plant under this name appear to be examples of either M. tuberosa “armata” or “bracteata”. This name is invalid.

Myrmecodia tuberosa is another readily available plant that has seen its popularity fade as new hydnophytine species make it to market. Nonetheless, as is evident here, a well-grown example of any of the forms is a very handsome "ant plant". They perform well under warm, bright, humid conditions but are not particularly tolerant of temperatures under 58 degrees F/14 C for any real length of time. The lowland Philippine forms are particularly prone to defoliate and rot and when kept too cool.

I have grown them since 2005 mounted on cork, in wooden and plastic baskets, in community trays and in plastic pots. I have found that they do best in hanging baskets. Mounted plants can look fantastic under the right conditions (see images here and elsewhere of wild plants) but are very slow when compared to plants that have their roots submerged in any free-draining substrate.

I grow the following M. tuberosa, strict sense:

Caudex detail, young mature Myrmecodia tuberosa sibuyanensis from Luzon island, Philippines.

Bako NP. Nice example of the species that shows variability as to the amount of ridging and root spines evident on the caudex when maturing. Plants grown very bright, dry and "hard" from youth will tend to have smoother and more globose caudexes, and will look little like the wet tropical greenhouse-grown specimen shown here.

sibuyanensis”. From seed collected in the lowlands of Quezon Province, Luzon, Philippines. Mostly inermous or very lightly-spined in youth, can develop soft, bristly root spines on the lower caudex when mature. Extremely cold sensitive.

Cool-grown young example of the intermediate "Tully" form of  Myrmecodia beccari  now in widespread cultivation throughout the world. Note ephemeral root spines on the right side of the caudex. These will be shed over time to leave the caudex more or less smooth.

Cool-grown young example of the intermediate "Tully" form of Myrmecodia beccari now in widespread cultivation throughout the world. Note ephemeral root spines on the right side of the caudex. These will be shed over time to leave the caudex more or less smooth.

Myrmecodia beccarii (both ecotypes)

Much better! An 18 month-old seed grown examples of the "spiny' northern form of M. beccarii, grown in a 4"/10 cm basket.

This is also now a mass-market exotic houseplant in the EU and the U.S.. Traditional wisdom holds that there are two distinct and easily-recognizable forms of this northeastern Queensland endemic, the southern or “smooth” ecotype and the northern or “spiny” one. Most plants in US and EU cultivation appear to originate from material collected off a Melaleuca tree by “Buchanan” along the Hull River, near Tully, Queensland. This found its way to Selby, where it was accessioned under #1989-0149. While this plant has mostly circulated as an example of the southern form, Australian hydnophytine growers have recently clarified that it is, in fact, an intergrade between the two main populations. Not surprisingly given this fact, plants in cultivation are extremely variable depending on the individual and growing conditions, with most young plants showing root spines, while most mature plants do not. As far as I am aware, there are only a handful of young examples of the true “spiny” northern ecotype being grown outside of Australia. I obtained a very limited amount of viable seed on trade in 2016 and have found the seedlings to be rather slow so far under warm greenhouse conditions, but are interesting-looking in youth.

The intergrade that is in wide cultivation shows a bit of cold tolerance, and I have had my plants exposed to 48 degrees F/9 C for short periods in both Guatemalan and California with no visible damage.

Two young examples of the "wet tropics" northern form growing in sphagnum moss in hanging baskets, compared to a two year-old intermediate form in pot with bark mix. California tropical greenhouse

Two young examples of the "wet tropics" northern form growing in sphagnum moss in hanging baskets, compared to a two year-old intermediate form in pot with bark mix. California tropical greenhouse

Note: while its white fruits were once considered unique in the genus and diagnostic for the species, whitish or greenish-white fruits are now known to occur on two apparently undescribed myrmecodias from the Philippines and western Papua Province, Indonesia.

There are recent reports of this species occurring further north and west of previously documented localities on the Cape York Peninsula that may prove to be a distinct, overlooked ecotype.

Myrmecodia platytyrea (incl. both subspecies)

Myrmecodia platytyrea subsp. platytyrea from East Sepik Prov, PNG in 8"/20 cm basket.

Another popular plant with beginners, particularly the more readily available northeastern Queensland endemic, subsp. antoinii. There have been a few accessions made of this plant from the Mossman Gorge in Daintree National Park north of Cairns, Queensland. They can achieve very large sizes in less than five years in cultivation and can be grown in large pots or baskets with equal success. This is a very spiny plant at all stages in life.

The taxonomy of this species is very confused. Huxley and Jebb (1993) consider plants collected in both extreme northwestern Indonesian Papua and Madang Province, eastern PNG as Myrmecodia platytyrea subsp. platytyrea and consider all the southern-southeastern PNG and Cape York, Australian plants as subsp. antoinii. Having now handled a large number of plants of known provenance, I believe that it is likely that there are two “good” species in Australia currently lumped under subsp. antoinii.

I grew a few very striking-looking plants in Guatemala of what I used to consider subsp. platytyrea that originated from old accessions made in what is now Kutini-Payamu NP in the Iron Range of Far North Queensland (see image at end of post). This population is quite distinct from the other forms now in cultivation. Like some plants from the southeast coast of PNG, these plants can show orange or reddish petioles when grown under bright conditions. Images provided by a correspondent in Cairns of a mature plant from the Iron Range grown unprotected in cultivation in northern Queensland also does not closely resemble plants from Mossman Gorge. Unfortunately, all my material in Guatemala was lost during the move, but I have recently obtained seed from this ecotype generated in cultivation from one of my Australian sources (see below).

Currently, there are at least five locality-specific forms being grown in cultivation, of which I have four.

These are:

subsp. antoinii ex-Mossman Gorge, Daintree, FNQ. Big, ferociously-spined and very popular. Surprising tolerance to cool temperatures but watch out for stem and caudex rot if kept too wet. This subspecies (although it may warrant full species status) appears to have a very restricted distribution around Mossman and has reportedly been subject to recent poaching of adult plants from the NP by villains.

Two foot/60 cm tall, 10 year-old seed grown example of Myrmecodia platytyrea subsp. antoinii from Mossman Gorge, FNQ, Australia. This plant has been grown very bright, wet and root-constrained. Potted and grown under warm, shady conditions it will grow very large, floppy succulent leaves and a bright green caudex.

Note: unlike the vast majority of hydnophytines, this one can really "bite"! Be sure and use protective gardening gloves when working with larger specimens. Spines are painful and difficult to extract.

This hydnophytine is exceptionally suitable for staging as a “bonsai succulent” and responds well to main stem pruning.

subsp. antoinii Sagarai Valley, Milne Bay Province, PNG. These plants entered very limited cultivation in the U.S. from seed a few years back and remain very rare outside of origin. As plantlets, they were originally confused with other Myrmecodia species that occur in southeastern PNG. Now at young flowering size, both of mine are showing several desirable characteristics, including stout, intricately ridged caudexes, short spines and reddish to maroon petioles when grown very bright. Plants photographed in nature by well-known hydnophytine expert Derrick Rowe that were growing fully exposed at this locality exhibit short spines and bright orange petioles.

subsp. antoinii Kutini-Payamu, Queensland, Australia. Very few Australian growers have tiny numbers of older, legally-acquired Myrmecodia platytyrea from the northern Cape York Peninsula in cultivation. Unlike the variety/species occurring further to the south (“good” var. antoinii), these plants seem to fruit infrequently. After years of trying to replace the unique material lost in Guatemala in 2012, a small number of seeds was again made available to me by an acquaintance in late 2018. Despite being caught up in the mail and USDA inspection for a few weeks in cool weather - often a death sentence for hydnophytine seed - a half dozen germinated immediately on arrival and are growing well.

subsp. platytyrea Sepik River, East Sepik Province, PNG (ex-Enrique Graf, Tropiflora #2998). This plant has at least one other accession number associated with it, so be aware they are the same thing. Like all of Tropiflora’s hydnophytine offerings, they have made their way across the Atlantic and beyond, so same comment applies to ostensibly EU source plants. Quite different morphologically in every way from subsp. antoinii and material from FNQ.  Not tolerant of cool temperatures at all and, like subsp. antoinii and M. dahlii, very susceptible to developing corky scars on their leaves when subjected to environmental fluctuations.

Left, young mature caudex of Myrmecodia platytyrea subsp. antoinii from the Sagarai Valley, Milne Bay Province, PNG growing in California. Right caudex of subsp. antoinii from Kutini-Payamu NP, Iron Range, FNQ, Australia being grown in Guatemala. Despite differences shown here, images of caudexes and stems of mature plants from both localities suggest very close affinities.

The next post in this series will deal with the first wave of “new” hydnophytine species that began to trickle out of origin countries and into western horticulture from 2006 through 2013, including the amazing blue-flowered Myrmephytum beccarii and others.

Exotica Esoterica