The pebbled-leaf anthuriums
Bullate leaves occur in a very wide range of plant families, both in tropical ornamentals and familiar temperate species such as primulas, nettles and some asters. Bullate is generally defined as “blistered”, “bubbled” or having semi-globular swellings. Since we are discussing leaf structure specifically, I would add “pustulate” and “pebble-textured” to the list. This feature adds interest to foliage, and many popular plants in horticulture show it. The common explanation for this adaptation is that it, a). increases the ability of the leaf to capture light from all directions by increasing total surface area and, b). repels water/facilitates quick drying of a leaf surface via channeled drainage. Both enhancements are of obvious value to plants growing in the low light, almost perpetually wet environments of tropical rain and pluvial forest understories. Accepting this as a reasonable hypothesis, it seems logical that species originating from tropical pluvial forests should show this feature in extreme form. There is a lot of evidence suggesting that this is indeed the case.
(click on image below to view slideshow)
In tropical aroids, bullate leaves are an attractive feature of many genera. Among those commonly-cultivated, it is found with some frequency in Anthurium, Philodendron, Alocasia, Rhaphidophora, Arisaema, Anubias, Amorphophallus, Dracontium, etc.
Many familiar anthurium species have bullate leaves, with rippling on the lamina evident to a greater or lesser degree. There are several that are quite well-known in ornamental horticulture that have been cultivated since the late 1800s, including the justifiably famous Anthurium veitchii. Others, like the odd-looking A. reflexinervium, are relatively recent introductions to tropical plant collections. Beyond just having distinctly waved, rippled or bullate leaves, there is a subgroup of approximately 20 species and hybrids that are remarkable for the degree to which their leaves have evolved distinctly papillose upper surfaces in response to microenvironmental pressures in native habitats. None can be characterized as common in cultivation, although a few are usually available on an irregular basis by nurseries that specialize in rare aroids.
These species include:
Anthurium luxurians, A. splendidum, A. kunayalense, A. debile, A. rotolantei (All Sect. Cardiolonchium), A. corrugatum, A. lapoanum, A. bernalii, A. aff. toisanense, A. rugulosum (All Sect. Polyneurium), A. cutucuense, A. arisaemoides (Both Sect. Dactylophyllium), A. clidemioides, A. flexile (Sect. Polyphyllium), A. radicans (Sect. Chamaerepium), A. unense (Sect. Urospadix), A. silvigaudens (Sect, Andiphyllum).
Anthurium luxurians x dressleri (J. Vannini), A. luxurians x papillaminum (ex-FL; J. Banta? remade in Australia), A. luxurians x crystallinum (A. Dearden), A. warocqueanum x rugulosum (K. Havlicek), A. radicans x luxurians (Selby BG, formerly in mass market TC mistakenly as A. radicans x dressleri Selby BG, another quite different-looking hybrid that was also made there four decades ago and remade by me in 2004), A. rotolantei x warocqueanum (E. Offolter). There are several promising novel hybrids from within this species group that I have made recently that are still at seed or seedling stage.
While the true locational origins of a couple of the species listed above remain uncertain (i.e. A. radicans and A rotolantei sp. ined.), all the others all originate from extremely wet forests. Most are middle elevation to montane cloud forest plants, two of which occur as high as 3,000 m (9,750’) in the NW Andes. The remaining species are lowlanders that require shady, very warm, wet conditions year-round to thrive. Almost all are terrestrial, with four species and two hybrids growing as hemiepiphytes or true epiphytes.
These plants make superb additions to any tropical plant collection that can provide them with the conditions they require. Since the species mentioned range from perpetually hot to quite cool climates, there should be at least a pair of species suited for most settings. From my own experience and comments by the few other people who have grown it, I would rank Anthurium splendidum as being by far and away the most challenging species on the list to cultivate and obtain and A. radicans being the easiest to grow and source. Whenever possible, locality data should be looked out for and paid attention to, since some of these species occur at wide elevational ranges that have obvious implications for their cultivation.
Growing media is a subject of considerable debate among tropical aroid growers. I have experimented with a number of products and blends over the decades and have settled on either pure long-fiber NZ sphagnum or a mix of 2 parts fine Orchiata bark, 2 parts medium Orchiata bark, 1 part coarse pumice or perlite, 1 part medium hort charcoal and 1 part medium tree fern fiber. To this mix I add encapsulated gypsum at recommended rates per volume being prepared, dolomitic limestone at same rate, and a balanced formula prilled, slow release fertilizer, preferably Nutricote.
I am not a big fan of sphagnum peat moss as a substrate. Some public gardens, especially in the EU, have a zero-peat policy in response to valid criticisms raised by the “bog people”. While many nurseries, particularly in the southeastern US, still use sphagnum peat and perlite as a standard mix to grow ornamental aroids, I have always found it challenging to work with. Nothing new or clever to say about it, really. When soaked it takes ages to dry, and when fully dry it takes ages to wet. Unlike sphagnum moss, which can be sustainably harvested (but probably isn’t in most places), peat extraction is open pit mining. Peat has its uses in ornamental horticulture but should certainly be used in a more rational manner and in FAR lower volumes than it is today.
Two relatively unrelated bullate-leaf Anthurium species from Neotropical cloud forests. Left, A. silvigaudens, a central Guatemalan endemic (Image: F. Muller). Right, A. rugulosum from Ecuador and Colombian high elevation Andean forests.
Two very showy upper elevation Ecuadoran Anthurium species from section Polyneurium in the author’s collection. Left the tall, upright hemiepiphyte A. aff. toisanense and right, the terrestrial A. corrugatum. Both of these plants require cool night-time temperatures and good water quality to develop and maintain perfect leaves like these in cultivation.
The epiphytes and hemiepiphytes on the list, especially A. clidemioides (above left) and A. cutucuense, should be provided with support of some kind. Options include narrow redwood or cypress studs, tree fern totems (now very costly but my preference still), virgin cork tubes, sphagnum moss-filled hardware wire tubes and coco fiber-wrapped poles.
Basic anthurium cultivation recommendations apply to all species. These plants do not respond well to root disturbance after seedling stage, they loathe anything stronger than a gentle breeze, and they prefer high humidity regimens no matter what their temperature preferences. In general, a shady environment is preferred. Higher light is tolerated by some species, but supplemental magnesium feeds should be added to offset the effects of higher light levels on the plants. Some species appear to be especially water quality sensitive, especially A. splendidum, A. debile and A. bernalii.
Above left, the southern Central American epiphyte, Anthurium clidemioides and A. silvigaudens from the central Guatemalan highlands (above right, image F. Muller).
Two extremely beautiful bullate (sometimes bubbled when mature) leaf anthuriums are shown below. On the left, the delicate and aptly-named, A. debile with blue-black leaves to >20"/50 cm from near sea level in the Colombian Chocó and Valle del Cauca Provinces, and my own hybrid on the right, the similar-size A. luxurians x dressleri, that combines a very dark-colored pebble-leaf Colombian species with a very dark-colored velvet-leaf Panamanian one.