[ Home ] [ Articles ]

Vol. 10(7), pp. 11-12The McAllen International Orchid Society JournalJuly 2009

Pl#301205-2. Dendrobium crumenatum Sw. 1799.

R J Ferry

This species came into the collection three and a half years ago, potted in a 6-inch clay pot, in red volcanic rock. The pot was dry, but overgrown with weeds. On depotting, a few resident pests were also discovered, the most numerous being small cockroaches. With other chores pressing as the last month of 2005 was drawing to a close, the depotted plant was "de-bugged," checked for scale and other obvious pests, and temporarily potted in pure New Zealand Sphagnum moss. It was received in late December, 2005, and on 2 January, 2006 was repotted into your editor's standard mix of Douglas Fir bark laced with a little New Zealand Sphagnum, and lodged in the greenhouse. By March, it was outside, hanging under the shade cloth of the home's back patio where it spent the summer while construction proceeded on the new, larger greenhouse.

In November, 2006 it entered the new greenhouse and was lodged in the northeast corner, at Station I-North where it would receive morning sunlight, but be shielded from the noon and afternoon light. It was watered frequently as were other mounted and potted terrestrial orchids in that area. The area's temperature was warm, but not nearly as warm as other sections of the greenhouse. In short, it was maintained in an area of generally fairly constant temperatures and humidity. In the greenhouse, it sent up long inflorescences with small buds, but then the rachis and buds became relatively dry and dormant. In fact they appeared dead.

Fig. 1. Pl#301205-2. Dendrobium crumenatum Swartz. Digital photo DSC_1771a.jpg 02 April, 2007.

Fig. 2. Part-inflorescence, Dendrobium crumenatum. Digital photo DSC_1772a.jpg, 02 April, 2007.

In March of 2007 it was back outside; once again hanging under the shade cloth of the back patio, and suddenly--in April--all the the "dead" inflorescences suddenly burst forth and began to show white flowers (Fig. 1)! What happened in the back patio that had not happened in the greenhouse, or had something happened in the greenhouse that was just now showing in the back patio with this flurry of white flowers (Fig. 2)?

In its natural habitat, this species flowers for most of the year, but under greenhouse culture it is known to do so, seemingly (to the orchidist) at strange times and for no apparent reason. Likewise, it may not flower what the orchidist expects! What's happening in nature that doesn't take place under greenhouse culture? The explanation is relatively simple. In areas of tropical Asia, one sees frequent rains which induce the vegetative growth. At the terminal portion of these growths, the long rachis grows and--at alternate nodes--the flower buds form. All is now set for another rain shower. Given a cooling rain shower that drops the temperature from say 35°C. to about 29°C. (about a ten degree drop on the Fahrenheit scale), flowering is initiated!

Fig. 3. Dendrobium crumenatum & inflorescences. Dig. Photo DSC_1777a.jpg 02 Aug. 2007

Another such rain-induced temperature drop took place a few months later, and it flowered again (Fig. 3). You get the idea: grow this species in intermediate-to-warm greenhouse temperatures and then--when you want a flush of flowers from it-- give it those few degrees of temperature drop and in a few days the plant's dormant buds will be sufficiently impressed to open flowers!

There's another interesting fact about this species. Don't be eager to cut off old inflorescences!! They may not only flower again, but they're prone to sprout keikis if the plant is watered, fertilized well, and kept under comfortable temperatures! The only real drawback to culturing this species may be its size. It can be grown in a relatively small pot, but it can put up inflorescences reaching a meter or more, so plan on giving this one a little vertical "elbow room!"

Copyright © 2009 R J Ferry