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Myrmecophytic Microgramma spp (with images)

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Greetings after another prolonged absence.


The amazing variety of forms and the ready commercial availability of Southeast Asian and Malesian ant fern species (Lecanopteris, Polypodiaceae) has made them justifiably popular among tropical plant collectors. They obviously find their biggest fans amongst those fern collectors that can avail themselves of warm, humid growing areas, but I have also noted over the past years that they also seem to find a following among orchid growers as well, particularly the common L. sinuosa and the rather showy L. mirabilis.


Until recently, the Neotropical ant ferns (Microgramma, Polypodiaceae) were somewhat difficult to find for sale in the US and the only species that were occasionally offered by specialty nurseries were M. brunei and M. lycopodioides. Based on comments made on this and other plant fora it appears that some clones of the former species in the trade can be challenging to grow (or are maladapted?), which has been an obstacle to more rapid distribution of this species in ornamental horticulture. Subsequent accessions from new localities and comments by friends at a couple US botanical gardens as well as my own experience indicate that M. brunei is an easy to grow - if untidy - fern under warm, humid conditions.


From a quick review, there are just over half a dozen described myrmecophytic Microgramma species, with the center of species diversity located in the wet forests of Peru with five species reported there. Besides Microgramma, there is a recent publication documenting the presence of external domatia on a completely unrelated fern from the Peruvian Amazon region (Polytaenium cajensense, Pteridaceae), so there are probably some interesting discoveries to be made in this field throughout the region.


I am currently growing four species of ant-associated Microgramma species, two of which form conspicuous tubers along their rhizomes (M. bismarckii and M. brunei), while another has ants excavate interior tunnels along the length of its rhizome (M. megalophylla) and the last is a common associate of ant gardens throughout the Neotropical lowlands. Besides these species, I also grow five additional species of microgrammas that are not known to have ant mutualisms. I am also working with nurseries in Ecuador and Peru to add another couple species (part. M. bifrons) to my collection over the next year.


I grow almost all my Microgramma species in hanging baskets filled wth NZ long-fibered dried sphagnum and topped with living sphagnum moss from either Ecuador or California. Once established, they are fertilized lightly but frequently with Maxsea as described elsewhere on this forum. Except for M. bismarckii and M. squamulosa, all species are grown in a warm, wet greenhouse. Light conditions throughout the growing area are bright for much of the day. Their growing media is kept uniformly moist to wet at all times and relative humidity is high.


Many readers here will be at least slightly familiar with most of the species mentioned previously. Since M. bismarckii is not yet a common fern in cultivation, note images showing the very striking tubers/external domatia. They are surprisingly large and have a very unusual form; with slightly sharp “horns” studding the very glossy surface. This characteristic is shared with at least two of its close relatives in Peru.


M. lycopodioides








M. megalophylla






M. brunei (recently divided)






M. bismarckii











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Great stuff Jay!  So well grown as usual, and very nice photos.


The only one I have grown is M. brunei.  I concur that it likes humidity and warmth.  I also make sure it has air movement around it.  I got that from an article by the American Fern Society about the culture of these plants (specifically on page 15).  Here is a link to that article:  http://amerfernsoc.org/ffa/Fiddlehead%20Forum/FF%20Volume%2035-36/Fiddlehead%20Forum%20Vol%2036%20No%202-3.pdf


I also discovered that for me, I get much better production of the tubers when I give the plants more light, when I have the plants close to my fluorescent bulbs.


While I do get ants moving into my Rubiaceous ant-plants once they get large enough and into at least a few of my Lecanopteris ant-ferns I have never had ants move into the M. brunei tubers.  Do you have ants in your M. brunei or bismarckii tubers Jay?

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  • 2 years later...

Tubers of a cultivated Microgramma bismarckii, at different stages of growth, becoming darker as they age:

A budding tuber, 4.5 mm wide. There is a small cavity in developing tubers. 
A green tuber in mid development.
A darker tuber in advanced development, 22 mm width, excluding "horns". 
The same tuber photographed months earlier.
The entrance is oriented in a similar position on all tubers, located on the inferior side adjacent to the rhizome connection.
A cross section of a tuber would be interesting to see.
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