The toothy Dendrobium serratilabium.

A quite widespread Dendrobium in the Philippines is D. serratilabium, a species found on Luzon and Mindanao, but with very localized populations in the provinces of Aurora, Quezon, Rizal, Laguna, Leyte, Bukidnon and Misamis. The species was described from plants collected in Rizal by Augustus Loher in September 1909, but was described only in 1937, by Louis O. Williams. The pseudobulbous, jointed stems are pendulous and dangle to around a meter in length, with glossy, dark green leaves; older branches are leafless. The inflorescences arise from near the stem tips and usually 6.5 cm long, bearing up to 10 flowers. These blooms are 3.2 cm wide but do not open widely. In common with related species, the mentum is long and spur-like, but the most distinctive feature, of course, is the labellum with toothy margins.

The faintly fragrant flowers of D. serratilabium are variably colored, but usually in a ground color of yellow or greenish, with or without dark brown tesselations. A plant I have seen from Mindanao have almost pure white segments tipped with pink.

There have been some questionable data regarding its altitudinal distribution. No altitudinal record was stated by Augustus Loher for his specimen and this lack of data was echoed by Valmayor in Orchidiana Philippiniana by not mentioning any information regarding the plants' elevation. However, in Cootes (2001), it was said that D. serratilabium occurs at elevations from 500-1200 m and this was followed in the Co's Digital Flora of the Philippines website. However, I do not remember Jim mentioning anything about finding this species in the wild, but I could be wrong. My own observations have been insufficient, but I have seen this species at an altitude of around 400 m asl, growing either as an epiphyte or a lithophyte, rooting on thin layers of moss in mixed dipterocarp forests and limestone forests usually in shade, but can, of course, be found at lower or higher altitudes, give or take a few hundred meters. Basing from plants I have seen in the wild so far, temperature extremes probably range from 37 C during the day to 15 C during the coolest months of the year, which is from December to February. Windchill factor during these cooler months surely allows the plants to experience lower temperatures.

These are easy plants in cultivation and an important prerequisite is that the roots should not be allowed to dry out for even a few days. Rainfall is diminished from March to early May but these plants obtain their moisture requirements from fog and dew. As mentioned earlier, the plant which served as the type was found to be in bloom during the month of September, and I have observed this species to be in flower during the months of January to March, August to September, and December, but this depends largely on prevailing climatic conditions. Healthy plants bloom twice or thrice a year.