Diggin' in the Garden. First for MEMBG? Maybe First Anywhere!

Early last fall I gave a tour to a group of my peers from the AABGA (American Association of Botanical Gardens and Arboreta). When giving tours, I always try to show off our beautiful vireyas, tropical rhododendrons from Southeast Asia. On that particular October day, in the vireya beds there was a plant of even greater interest, Deppea splendens, a five-foot tall shrub of the coffee family (Rubiaceae). It is one of the few living individuals of a species now presumed to be extinct in the wild. The first viable seeds ever produced in cultivation may have been developing on this plant. Earlier in the month, I had successfully cross-pollinated two different clones of D. splendens to get developing fruits on both plants. Previously, the only way this species had been successfully propagated in cultivation was asexually, either by cuttings or by air layering.

Dennis Breedlove of the California Academy of Sciences made the first collection of the plant in 1972, when he pressed specimens for his work on the flora of Chiapas (Phytologia 63: 43-47, 1987). In 1981 Dr. Breedlove returned to that same site in Chiapas with Bruce Bartholomew and collected seeds from the only plant ever recorded in the wild. They distributed seeds to botanical gardens at UC Berkeley and The Huntington, from which we received our plant in 1982.

Deppea splendens is considered to be the showiest member of its genus. It has corymbose inflorescences with two-inch-deep, yellow to orange flowers that dangle from a six-inch-long, wiry peduncle (Pacific Horticulture 61, 8-9, 2000). Deppea splendens seems to respond quite favorably to our climate in Westwood, and may even prefer our microclimate over that of other California gardens. At MEMBG, D. splendens continuously produces flowers up to five months running, with peak flowering during the fall. We received a second plant in 1998, which flowered in its container during the fall and thus gave me an opportunity to swap pollen. Probably in the wild this flower would be pollinated by hummingbirds (see cover article,"Why Do Our Hummingbirds Hum?"). But not leaving anything to chance, I pulled out my trusty small-tipped paintbrush to ensure pollen transfer between flowers on the two plants. Even though I was the pollinator this time, quite likely this would happen naturally if genetically different plants were growing near each other.

Twenty weeks later the first seed capsules--two of theme--were harvested from the container-grown plant in our lathhouse. Even though all pollination was performed on the same day, the plant in the vireya bed yielded two more capsules during week 25. In all, the capsules contained more than a thousand seeds--WOW!

I was very excited to find out whether the seeds were alive, and proceeded to test seed viability. And I wasn't disappointed! Some interesting observations to date have been that the seeds germinated easily (98%) under a temperature regime of 29 oC day/18 oC night, low natural light, and 70% to 80% relative humidity. Germination occurred after 16 days and peaked at 21 days. Mortality was very high when transplantation was performed at the radicle and cotyledon stages. Now I am investigating different methods of transplanting, but, to date, the best method has been to sow seeds with enough space between them--for example, using plug trays--that seedlings can grow without interruption.

The seedlings of D. splendens at MEMBG may have a very important future, if this species will ever again see its native range of Chiapas, Mexico. Currently, we are involved in obtaining as many genotypes (genetic forms) as possible of the plants first grown from the seeds collected in Chiapas, to establish a breeding program and further our efforts in sexually propagating Deppea splendens. At present, there may be clones of as many as eight genotypes, all of which could be used to broaden the gene pool. This work will be essential if an ex-situ conservation effort is to be mounted. Wouldn't it be wonderful to reestablish this beautiful plant back to its neotropical habitat in the mountains of southernmost Mexico and neighboring Guatemala? I can report that the AABGA group was very impressed with our efforts. Along with many others, they will be eagerly awaiting answers to the many questions that returning a plant back to nature incurs.


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