Orchid Q&A

Q.

I have been an amateur grower of orchids for a long time, cultivating my plants in a greenhouse environment on my small farm located in the interior of my state in Brazil. This place is located 1,970 feet above sea level. In the summer it reaches 100º F and in the winter it averages 55º F, with some days as low as 40º F. I do not cool or heat my plants. Unfortunately, for some years I have noticed that many of my plants (about 2,000) have a deficiency or eventually some illness. The leaves become yellow at their apex (upper part of leaves) and I am not able to detect the cause, even in a laboratory examination. This yellow coloration then extends down the pseudobulb. I haven&39;t noticed any damage on the new shoots. The plants that show more problems in flowering are the Laelia purpurata types. My plants are grown in tree fern. Helio Luco

A.

I believe your plant's problem is nutritional, rather than a disease. The yellowing leaves are all on the oldest pseudobulbs, which shows that the plant is taking nutrients from them and using these nutrients to maintain growth. Very likely it is a deficiency of nitrogen, but it is also possible that a lack of iron and other elements is the cause of the problem.

Try a slow-release fertilizer called Nutricote. It is formulated in Japan for a similar temperature range to what you experience. The eight- to nine-month formulation, when applied in spring will basically carry you through until the following spring. If this is not possible to obtain, any good slow-release product or a balanced liquid fertilizing program will start your plants into rapid growth. Also, the minor elements need to be supplied, especially calcium, as you are growing in tree-fern fiber. If you do not have a liquid fertilizer with calcium in it then you should consider adding six pounds dolomite lime to each cubic yard (3 Kg/cm meter) of tree-fern fiber and mix in well. Andy Easton

Orchid Q&A