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. This place is located 1,970 feet above sea level. In the summer it reaches 100 F and in the winter it averages 55 F, with some days as low as 40 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’t noticed any damage on the new shoots. The plants that show more problems in flowering are the Laeliapurpurata types. My plants are grown in tree fern.

A l 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.