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Cultivation of the epiphytic ant-plants Hydnophytum and MyrmecodiaThis article was originally published in Cactus and Succulent Journal 72:142-147 (2000).
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Figure 1: Myrmecodia tuberosa in Sarawak. As seen here, Myrmecodia plants frequently grow with the tuber hanging down. Photograph by Wilson H.P. Chua. All remaining photographs by the author. |
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Despite their close relationship, it is easy to distinguish Hydnophytum from Myrmecodia. Myrmecodia tend to have just one or a few thick, unbranched stems with large leaves (exceptions are M. lamii and M. beccarii). The stems of Myrmecodia are frequently covered with clypeoli, unusual shield-like structures surounding each leaf base. The clypeoli may be bordered with spines, and they give the stem a curious armored appearence. It should be noted, however, that in some Myrmecodia species, the clypeoli are obscure or absent. Myrmecodia flowers form in hollows called alveoli which develop along the stem between the clypeoli. Hydnophytum have thinner stems with longer internodes and smaller leaves. They often have multiple stems which can be branched. The stems lack clypeoli and alveoli.
Myrmecodia tubers often have ridges and wart-like bumps; one unimpressed family member told me that my myrmecodias look as though they have a nasty skin condition. The tubers are frequently covered with spines, actually modified roots, that can be simple or branched. In contrast, Hydnophytum tubers generally lack spines, although one species in cultivation does have ridges. Tuber shape in both genera is very variable, and color ranges from dark brown to silvery grey.
The range of Hydnophytum extends from Malaysia and the Philippines, south to the Cape York Peninsula in Queensland, and east as far as Fiji. It includes southern Thailand, Cambodia, and Vietnam. Myrmecodia has a similar but slightly more restricted range, with the highest species diversity in New Guinea (Huxley and Jebb, 1991; Huxley and Jebb, 1993). Unlike many epiphytes, ant-plants are quite rare in lowland rainforest. More typical habitat is open woodland where the plants are exposed to bright light; in myrmecophyte habitat, nutrient availability probably limits growth, while in deep forest, lack of light would reduce the benefit from additional nutrients provided by ants. The plants are found more frequently on branches than trunks (Huxley and Jebb, 1991) and can be very common in disturbed habitat such as plantations (Huxley, 1978). During the time that he studied Hydnophytum formicarum and Myrmecodia tuberosa at Bako National Park in Sarawak, Janzen (1974) noted that rain fell almost daily in the afternoon.
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Figure 2: Hydnophytum species mounted on bark).
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Figure 3: Hydnophytum species with ridged tuber. The leaves have more prominent veins than those of the plant in Figure 2. This is a three year-old seedling growing in an 8 inch bulb pan. The plant is 27 cm (10.6 inches) tall with a tuber diameter of 12.5 cm (4.9 inches). |
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Figure 4: Hydnophytum seedling with prominently ridged tuber Compared to the plant is Figure 3, this seedling has narrower leaves and a more prominently ridged tuber. It remains to be seen whether these characteristics are retained at maturity. The tuber is 6.5 cm (2.5 inches) in diameter. |
These plants seem to be easier to grow than the first group and are less likely to shed leaves when underwatered. Other species may be growing in botanic gardens, but they are not widely available to amateur growers. Unfortunately, I have not been able to positively identify any of my Hydnophytum plants, due to the difficulty of finding literature on the genus.
The genus Myrmecodia has been recently revised by C.R. Huxley and M.H.P. Jebb (1993), so cultivated myrmecodias are easier to identify. The majority of myrmecodias offered for sale are forms of the widespread and very variable species Myrmecodia tuberosa (see Figure 1 and Figure 5).
Figure 5: Myrmecodia tuberosa seedlings. Left, M. tuberosa from Bako National Park, Sarawak, Malaysia. This plant may correspond to Huxley and Jebb's (1993) M. tuberosa "bracteata." Right, The variety sold as Myrmecodia solomonensis (Huxley and Jebb's M. tuberosa "salomonensis"). Both seedlings are one year old and about 9 cm (3.5 inches) tall. |
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Other plants in my collection include a young M. beccarii and a plant from New Guinea which might be M. platytyrea (see Figure 6).
Figure 6: Myrmecodia species from Papua New Guinea.
This mature plant seems to fit the description of M. platytyrea (Huxley and Jebb, 1993). Clypeoli and alveoli are visible on the stem. The plant is growing in osmunda fiber in a 4 inch clay pot. The tuber is 13 cm (5.1 inches) long. |
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The related genera Anthorrhiza, Myrmephytum, and Squamellaria, do not seem to be widely grown. I am aware of a single Anthorrhiza specimen on display at the University of Oxford Botanic Gardens in England, but no others. I would definitely be interested to hear reports of other plants in cultivation.
The myrmecodias common in cultivation are lowland species found at altitudes below 1000 meters (Huxley and Jebb, 1993). The hydnophytums are also likely to be lowlanders, though this is uncertain in the absence of collection data or definitive identification. The habitat preferences of ant-plants summarized above would suggest cultivation in warm temperatures with high humidity and bright light, though some protection from mid-day sun may be warranted. In North Carolina, I grow my plants outside in summer where they experience high humidity and direct sun after about 2:00 pm. Daytime temperatures are commonly 90-95 ûF (32Ð35 ûC), and nighttime temperatures drop to the 60's (15Ð20 ûC). I would not risk prolonged exposure to temperatures much below 60 ûF (15 ûC). In winter, the plants grow under fluorescent lights with my orchid collection or on a sunny windowsill.
Many growers successfully use a mix of peat and perlite, but I prefer a combination of long-fiber sphagnum moss, chopped fir bark, and perlite which is very open but retains moisture. The plants are watered when the mix is just barely moist, because sphagnum is difficult to re-wet if it is allowed to become bone dry. Either plastic or clay pots are suitable depending on one's watering habits. If humidity is high, plants can be mounted on cork bark or treefern plaques for a more natural appearence (see Figure 2). Mounted plants will, of course, require more frequent watering. The roots of Hydnophytum and Myrmecodia are very brittle, so great care must be taken when repotting. Luckily, however, the plants seem capable of producing new roots from any part of the tuber that is in contact with a moist substrate.
Jolivet (1996) reports that cultivated plants without ants are stunted, but this does not seem to be the case if plants are fertilized. Any balanced fertilizer with trace elements should be suitable. I use Dyna-Gro 7:9:5 at a rate of 1/2 tsp per gallon every second watering, and I throughly flush the pots with water on days when I do not fertilize. Sphagnum moss frequently sprouts from spores in my potting mix, indicating that this procedure prevents buildup of fertilizer salts. Moss growth is especially luxurient in flats of seedlings which are never allowed to dry out.
In addition to occasional infestations of mites, my myrmecodias seem especially prone to developing ugly brown bumps on the leaves. The bumps begin as whitish swellings on a newly developing leaf and later form a hard corky skin. These defects occur on plants from a variety of sources, and some photographs of wild plants show evidence of the same problem. I suspect that this is not a disease, but rather that it is edema due to low light and excess water. The defects are most severe during cool, dull winter weather and much reduced or completely absent in summer when the plants receive more sunlight. In addition to increasing light intensity, reduction of watering may also help, though underwatering will result in defoliation is some species. Interestingly, my hydnophytums seem immune to this problem, and in Myrmecodia beccarii, the defects are generally restricted to the petiole. Perhaps the thicker leaves of these species are more resistant to the swelling.
Cold wet weather, injury during shipping, or other accidents may result in rotting of the tuber. This can disfigure the plant but need not be fatal if caught early. The rotten portion should be scraped off to expose healthy tissue and dusted with something to dry out the wound. I have used powdered cinnamon, which among orchid growers is reputed to have anti-bacterial properties. If necessary, the plant can be repotted so that the injured portion of the tuber is not in contact with wet potting mix. Small seedlings will occasional lose their growing stem to rot if they are too wet during shipping. As long as the tuber remains firm, these seedlings should be potted up, as they often sprout new stems and may produce interesting multi-branched specimens.
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