Friday, January 10, 2014

Eulophia petersii

Eulophia petersii flower.
The Orchidaceae (orchid family) is the largest family of flowering plants, comprising something on the order of 25000 species. The orchids are most diverse in the tropics growing as epiphytes on the trunks and branches of trees, although even here in Connecticut we have a number of native species. Most of the epiphytic orchids are more or less succulent (unlike our native woodland and bog orchids), as an adaptation to surviving the short periods of dryness that can even afflict plants in the tropical rainforest, if they are growing attached to bark without soil.
Although they are much fewer in number of species than the tropical epiphytic orchids, there are succulent orchids that live in true desert environments. Eulophia petersii is one of the most widespread of the desert orchids, occurring over much of eastern Africa, from South Africa to Somalia. The plants grow in shallow soil over rock outcrops, or in dry sandy soil, in areas with a warm, dry climate with rain primarily in summer.
Eulophia petersii plants consist of clusters of squat, fat green stems (called pseudobulbs in orchids) that bear a small number of succulent, sharp-edged leaves. The plants are evergreen and the leaves can persist for several years, but the actual growth of the plants is highly seasonal. New pseudobulbs and foliage are produced in spring and summer, and tall racemes of flowers bloom in mid-summer. In the winter, the plants are dormant and can withstand weeks or months without water. 
Eulophia petersii plant with succulent leaves and pseudobulbs.
In cultivation, E. petersii plants are not difficult to grow in conditions similar to those favored by agaves and echeverias. It may help to use a soil that is especially coarse and free-draining, though general-purpose cactus and succulent mixes should be acceptable. In summer, a fairly generous watering and fertilizing regime produces good results, as long as the plants get plenty of sun. In winter, E. petersii should be watered lightly and infrequently and kept in a cool, sunny location. Home propagation of Eulophia is probably only practical by dividing older clusters of pseudobulbs. Cultivated plants do set seed if pollinated, but as with other orchids the seeds are minute and require exacting conditions, possibly including the presence of symbiotic fungi, in order to germinate and grow. I've never had any luck trying to start the seeds by sprinkling them in the soil around the parent plants.