Friday, December 25, 2009

Diplosoma luckhoffii

Diplosoma luckhoffii (MRO209, east of Bitterfontein, Western Cape), a little over a year old from seed. Flower about 1 cm wide.

Diplosoma luckhoffii is a tiny winter-growing succulent from South Africa. The plants are completely dormant for much of the year, persisting as button-like bodies at or just below the soil surface, protected by a layer of dried up leaf tissue. When rain and heavy dew wet the soil in the cooler months, Diplosoma cracks out of its shell and sends up a pair of mushy green leaves, covered with sparkling, bubbly water-storage cells ("bladder cells"). Flowers are produced in mid- or late winter. The flowers often don't open very well, at least in cultivation, but set seed easily, and even self-pollinate sometimes.

Quartz flats in the northern Knersvlakte, where I collected Diplosoma seed in 2004.

Diplosoma luckhoffii is endemic to the Knersvlakte, a very clearly defined patch of desert only a few hours drive north of Cape Town. The Knersvlakte is characterized by low, rolling topography with frequent patches of snow-white quartz gravel. Not all of that quartz is entirely natural, and one occasionally runs across pieces that were shaped into blades by stone age people. Diplosoma, along with a diverse assemblage of other dwarf succulents in the Aizoaceae (mesemb family) and other families, lives only on soil with a dense cover of quartz rubble; the quartz moderates the temperature at ground level, and makes it possible for stubby little plants to survive the summer without cooking.

The cultivation of D. luckhoffii is fairly difficult. The plants are short lived, not usually surviving for more than three or four years even under ideal conditions, and as a consequence are never available except as seed, as far as I have seen. Diplosoma seed is almost as fine as dust, and should be sown in autumn on the surface of a mineral soil (sandy loam leavened with perlite, vermiculite and course sand) in the pot where they will stay permanently. Seedlings and mature plants alike demand brilliant sunshine, cool night temperatures and careful watering when active. The soil should dry out slightly at the surface between waterings, but remain slightly moist below ground at all times. During the warm-weather dormancy, pots of Diplosoma can be left dry, aside from an occasional misting on sunny days. When happy, Diplosoma sometimes flowers at the end of its first season, though more often the plants rot or terminally desiccate while still pinhead-size.

I have never heard of Diplosoma being successfully cultivated outside of a cool, airy and brightly-lit greenhouse, but I know someone who is trying it under fluorescent lights (right next to the tubes, for maximum illumination). It will be interesting if she succeeds!

Monday, December 21, 2009

The Shortest Day

Happy (northern winter) solstice! The day will be 1 second longer tomorrow, in my neck of the woods. This photograph is actually of a minor snow event earlier this month, not the Christmas air travel schedule crusher from this past weekend. The current snow pack is much more impressive, but not as pretty.

Wednesday, December 9, 2009

Epiphyte Tree at UConn Greenhouses

One of the big events this past fall here at the University of Connecticut greenhouses has been the completion of an epiphyte tree in the entryway, which had previously been somewhat cramped and lacking in focus. The new entryway provides space for tours to assemble, and a point of interest to draw visitors in.

Epiphytes are plants that live on the surface of other plants, using their hosts for support but not acting as parasites. About the only epiphytes that occur naturally here in Connecticut are tiny mosses and liverworts that grow on tree trunks, but in tropical climates trees may be festooned with diverse communities of orchids, bromeliads, ferns and others.

The UConn epiphyte tree was put together over the summer, with many hours of volunteer help from the Connecticut Orchid Society. It is constructed around a skeleton of steel pipes clamped together into a hexagonal trunk, with additional pipes jutting out above head level to create branches. The trunk is covered with panels of expanded metal, which do a good job of rounding out the angular underlying structure. All of the basic structural materials were recycled from old bench parts from the greenhouses.

Clint Morse and members of the C.O.S. assemble the epiphyte tree's internal skeleton.

Probably the most time-consuming part of the construction of the epiphyte tree was covering it with bark. We used natural cork oak bark, which is harvested—sustainably, without killing the trees—in the western Mediterranean region. The C.O.S. and greenhouse manager Clint Morse laboriously fit pieces of bark together, sometimes cutting them to fit or softening them with steam in a large autoclave to mold them into the right shape, then wired them in place. Gaps were filled in with slivers of bark glued in place, or clumps of coconut fiber. The branches of the epiphyte tree were covered with special ordered bark tubes (taken whole from smaller cork oak trunks).

Some of the initial plantings were done as the bark was being fit into place, using epiphytes already established on pieces of cork. More plants were wired or glued into place later, and these should anchor themselves and spread with time. We’re still working on fine-tuning the tree and its plantings, but stop in and check it out if you’re in the area!