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An introduction to cultivation.


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This article now fractionally improved was written for a Polish journal.  If there is anything that needs clarifying then perhaps our experienced growers can add comments.  What was clear in my head may not be to others. It is very generalised in its scope because ant-plants are found in a number of unrelated plant families and a substantial number of species are extremely rare to being non existent in cultivation; indeed numbers are probably yet to be discovered. Also their native habitats vary from hot and humid lowlands to near alpine conditions but almost always in the tropics.


The Cultivation of Ant-house Epiphytes.

Derrick. J. Rowe.

Many plants that provide homes to friendly ant colonies are not at all succulent in form; however, here we are concerned with a small number of plants with specialised forms and physiologies that permit survival of the numerous short droughts inherent to life perched in the trees of more or less seasonally-dry tropical climates.  Perhaps surprisingly, dry bark or soil in contact with plant roots has a drying force many times greater than that of equally dry air. (Benzing 1990.)  Terrestrial arid-land plants can relieve this problem by allowing their roots to shrink during drought, thereby creating insulating air gaps.  Epiphytes (tree living plants) are not able to do this; therefore, it is not surprising that many have evolved essential survival adaptations.

  There are notable exceptions but most tree-living ant-house plants are as xerophytic (aridity adapted) as numbers of plant species that although not strictly succulent are regularly accepted in the collections of succulent plant enthusiasts and many others have sufficient water-holding tissues to qualify as being fully succulent plants.

  Epiphytic ant-house plants are extremely diverse in their phylogenetic origins.  There are ant-house asclepiads, bromeliads, gesneriads, Melastomataceae, orchids, Solanaceae (potato family), Rubiaceae (coffee family), some New and Old World fern genera and Selenicereus wittii a particularly unusual epiphytic cactus may also qualify.  Cultivation procedures must inevitably vary across such an enormous range of plant forms, yet there is an important difference that separates all ant-house epiphytes from arid-land plants such as terrestrial cacti and that is their need for humid air.  This is why orchid cultivators often have greater success maintaining ant-house plants than do growers of succulent plants.

  Note that I frequently use cautious words like “most” because among most plant groupings there are exceptions to most horticultural guidelines and there are very few invariable rules such as the humidity requirements of ant-house plants.

  Another necessity is greater warmth than that required by most terrestrial succulents, particularly for ant-house species originating from tropical lowlands.  This especially applies overnight because lowland humid climates do not experience the severe temperature drops typical of arid climes.  Yet although all epiphytic ant-house species originate from tropical latitudes, quite a number of them occur at distinctly cool to even cold, high-mountain altitudes.  Such species would suffer severely in the high, daytime heat-accumulations possible in cacti aridariums, especially those with typically dry atmospheres.  Conversely, very few ant-house species will cope with frosts except perhaps species such as the truly bizarre Myrmecodia brassii a giant ant-house plant reaching an enormous 2 m., (6.56 ft.) in total length.  Its New Guinea habitats reach into sub-alpine scrub forests at altitudes of 2100- 3600 m. (6890- 11811 ft.) where it sometimes grows terrestrially and may have small frogs or lizards living inside.  Even here, close to the equator yet at heights around 2 miles high, there can be snow and ice overnight.  (The site www.wistuba.com has photographs of the equally fascinating and very similar M. lamii from the same habitats.)

  It follows that there is a cultivation divide between plants that originate from hot lowland habitats and those that originate from much cooler highland sites, yet for many species, milder (human comfortable) temperature gradients are preferred; in other words, not too hot and not too cold and with no frosts at all.  These mild-climate requirements mean that most ant-house plants are not suitable for the high temperature ranges typical of cacti houses where most plants originate from habitats that experience very dry atmospheres.

  Yet having stated this, author Attila Kapitany, in Melbourne, Australia uses a large bathtub of water in one of his plant-houses primarily as a heat sink; a strategy that enables a measure of protection from overnight temperature drops as daytime heat is re-radiated back to the night air of the glasshouse from sunlight warmed water.  Arranged along the edge of this tub is a selection of Australia’s tropical ant-house plants that grow very successfully.  Melbourne sits far south of the tropics and has a climate that can be cool, wet and humid in winter yet extremely hot (sometimes as high as 45o C.) in high summer when very dry air, flows in from the central deserts.

  Fortunately many species make excellent houseplants if placed in bright positions.  Indeed, because they require regular watering and many are extremely rare in cultivation, they are perhaps best suited to small indoor collections if in cold-temperate climates.  Those persons possessing a conservatory will be able to provide conditions permitting much larger collections.

  Another group of hobbyists that may have experience with ant-house plants, often without knowing it, are bromeliad cultivators especially those that prefer the beautiful silvery-leafed air-plant species.  Tillandsia baileyi, T. balbisiana, T. bulbosa, T. butzii, T. caput-medusae, T. paucifolia, T. pruinosa, T. pseudobaileyi, T. seleriana and T. streptophylla all have swollen bases, (technically pseudobulbs) inhabited by ants in habitat and they are easy plants to obtain commercially.  They are attractive, unusual, extremely easy to maintain and excellent introductory ant-house plants and although a little frost sensitive, they only require mild temperature ranges.  Indeed, these are probably the group of ant-house plants that should only be grown mounted with no potting media.  There are other bromeliads without pseudobulbs that also house ants including a few water-holding species.

  Experienced orchid and bromeliad cultivators will be very aware that epiphytes do not experience concentrations of fertiliser salts in nature.  Therefore water soluble, orchid-suitable fertilisers must be very well-diluted but applied regularly throughout warmer weather and they should be periodically flushed with room-temperature (preferably rain) water to avoid toxic accumulations.

  Specialist growers of carnivorous plants sometimes know a little about epiphytic ant-house plants because both groups have certain similarities; not the least being their abilities to survive in extremely nutrient poor environments.  Yet both groups are fractionally better fed than most other plants in their environments due to their manipulations of ants and other small fauna.  One should never plant members of either group in nutrient-rich substrates but ant-fed plants obviously grow and flower best with modest fertilising if they have no resident ants to feed them. (Indeed, there is ever emerging evidence that much faster growth of rubiacious ant-plants can be attained by using high nitrogen fertilisers.)

  Local hobbyists with experience growing somewhat similar plant groups can often give useful advice regarding such subjects as minimum heat temperatures because a setting suitable for one climate may not suit others.  Here in northern New Zealand, I live in a somewhat Mediterranean climate very near the cool end of the subtropics; therefore, I can successfully use a much lower heat setting than those in colder climates because of my longer warm periods. 

  Most ant-house plants may be grown mounted on timber or tree fern etc., slabs with zero potting media but success is then harder to achieve because this demands very regular misting and watering allied with higher humidity levels, so it is perhaps a choice only for botanic garden collections or very dedicated hobbyists.

 A universal rule for their potting media is that it must be well drained yet able to retain sufficient water to maintain plant health between waterings.  In other words a potting mixture must be related to one’s ability (sufficient time) to maintain necessary regularity of waterings.  Appropriate mixes of hardwood orchid chips (various grades,) barks, osmunda or other fern fibers, pumice or diatomite sands/gravels, peat, and preferably living, long-fiber, sphagnum moss have all been used successfully.  One must be careful of decomposing ingredients; plant loss due to rot can be a problem making long-dead, wet, sphagnum moss a suspect ingredient.  Australian growers have very effectively used coarse gravel substrates for their native Hydnophytum and Myrmecodia species, yet some use porous diatomite or pumice and peat based mixtures for Lecanopteris sinuosa that can grow on the very same trees as the former species in habitat.  Rot sensitive species may be kept in smaller pots that inherently dry faster.

  How much to water and when will depend on the overall growing conditions one is able to provide, linked to one’s local climate and current weather.  In hotter conditions watering and humidity levels may be kept fairly liberal as long as potting media is allowed to dry somewhat in between, but in ever colder conditions plants are best kept drier - within reason.  In winter use warmer (sunnier?) weather opportunities to water dehydration-stressed plants in the mornings so that any excess water has time to dissipate before the cold of night.

  Most ant-house plants including Lecanopteris ferns and Amazonian orchid species experience somewhat to much drier habitat conditions during their shorter day, dry-seasons (using the word winter is of little use in the tropics) and of course dehydration risks are accentuated for plants perched on trees.

 The very water-conserving crassulacean acid metabolic (CAM) pathway is very common in succulent plants and even more common among epiphytic flowering plants. (Luttge 2004.)  Myrmecodia beccarii uses CAM (Tsen et al. 2012.) as does Dischidia major (Treseder et al. 1995.) and future testing will probably find that the pathway is found in most epiphytic ant-house plants; providing further evidence of their xerophytic forms and especially physiologies.

  Hopefully these brief notes will provide enough hints to provide adventurous hobbyists with a measure of intuition - a feeling for how best to cultivate a truly weird group of plants within the limits imposed by grower’s local climates.  Gaining practical experience is not difficult for those that observe their plant’s responses to whatever treatments given but bear in mind that these are not plants adapted to many months of extreme drought while standing fully exposed to intense desert sunshine as for example are the large cacti.  Ant-house plants have evolved to endure shorter but regularly repeated periods of drought, relieved somewhat by the very humid atmospheres of the tropics.

  Now that Attila Kapitany has done so much to promote what were the largely unknown weird and wonderful Australian xerophytes and succulents; ant-house plants are probably the very last frontier of xerophytic plants.


Benzing, D. H. 1990. Vascular Epiphytes: General Biology and Related Biota. Cambridge Tropical Biology Series, Cambridge University Press.

Kapitany, A. 2007. Australian Succulent Plants: An Introduction. Kapitany Concepts, Australia.

Luttge, U. 2004. Ecophysiology of Crassulacean Metabolism (CAM) Annals of Botany 93: pp629- 652.

Rowe, D. J. 2010.  Ant-plants: Arboreal Wonders of Nature. DVD with many photos distributed by the Australian Cactus & Succulent Society.  http://www.australiansucculents.com/  But no longer.

Treseder, K. Davidson, D. W.  Erhleringer, J. R. 1995. Absorption of ant-provided carbon dioxide and nitrogen by a tropical epiphyte.  Nature Vol. 375: pp137-138.

Tsen, Edward W. J. Holtum, Joseph A. M. 2012Crassulacean acid metabolism (CAM) in an epiphytic ant-plant Myrmecodia beccarii Hook. f. (Rubiaceae.)  Photosynthesis Research.

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Crassulacean Acid Metabolism (CAM.)

It is well known that plants exchange essential gasses with the atmosphere through minute leaf openings named stomata alongside a process called transpiration.  About 94% of all plant species must transpire in daylight simply because photosynthesis requires the energy of light to convert carbon dioxide (CO²) into plant foods but most species cannot store this gas for later use.

  During transpiration, water is inevitably lost to the atmosphere through opened stomata and plants must continually replace this loss or desiccate and die.  Because few arboreal habitats provide entirely dehydration-safe environments, plant species from many unrelated families have independently evolved a rarer water conserving photosynthesising pathway termed Crassulacean Acid Metabolism (CAM.)  CAM plants open their stomata primarily overnight when lower temperatures and higher relative humidities ensure that transpirational water losses are considerably reduced.  Therefore, except for dehydration-safer periods close to dusk and dawn, they keep their stomata closed during daylight hours.  CO² as it is absorbed overnight is stored within vacuoles (large storage cells) as a constituent of an organic acid, usually 4-carbon malate.  During the following daylight hours, stored acid is progressively catabolised (broken down) so that its CO² can be immediately accessed for use in photosynthesis while stomata remain closed. CAM is a very water use efficient pathway but it usually imposes slower plant growth than that of ‘normal’ daylight-pathway C3 plants (but see next chapter.)  However, many epiphytes can take their CAM ability further because whenever rain arrives, they are able to switch rapidly to the growth-faster C3 pathway. Called facultative CAM plants, they switch between pathways as rain events come and go; an ability obviously of great advantage to plants that are subject to highly irregular water fluxes while perched in trees.

   A little fewer than 90% of all plants use the C3 pathway, while about 4% use the more energy efficient four-carbon fixing pathway C4.  Both C3 and C4 plants cannot store CO² so they must open their stomata in daylight.  The C4 pathway is best suited to plants in warm, humid climates with high irradiance.  A well-known example is Sweet Corn (Maize) Zea mays.  The balance of about 7% of all plant species use some form of CAM, which perhaps surprisingly, is an exceptionally common pathway of epiphytic plants. Indeed, an estimated 57% of all epiphytes use CAM in one form or another; a percentage “far outnumbering that found in typical terrestrial arid land species such as Agave, Cacti, and Euphorbia etc.” (Luttge 2004.)  I expect that as ever more species are tested, epiphytic myrmecophytes will prove to have a higher percentage of CAM than the average.

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CAM and Osmosis.

Water containing chemical solutions will flow across selectively permeable membranes from lower concentrations to higher concentrations until equilibrium is reached.  This force is called osmosis and is used by plant roots to extract moisture from their environments and by plant cells (supported by special water conducting xylem and sieve cells in vascular plants) to diffuse water and its chemical contents to wherever it is needed.

  Because CAM species manufacture and store CO² enriched organic acids, high overnight concentrations of such solutions increase plant osmotic potentials, hence improving their abilities to extract water from their immediate surrounds. This effect is most apparent towards night’s end when such acids are at their highest levels; hence, it is hypothesized to be of particularly benefit to plants in moist, tropical forests where dew formations occur mainly during the late dark period. (Luttge 1986; Eller and Ruess 1986; Ruess et al. 1988; Eller et al. 1992; Murphy and Smith 1998, cited by Luttge 2004.)

  One presumes that an improved ability to imbibe overnight dew may also advantage the many CAM members of terrestrial succulent species such as the Mesembryanthema of the Aizoaceae that inhabit the coastal fog belts and Succulent Karoos (dry places) of south western Africa.  The Karoos certainly have frequent fogs, and heavy dews that sustain many miniature succulent species.

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