Cattleyas and heat stress

Thursday, June 11, 2015

Reminder: if you grow cattleyas and their hybrids on wood, which many of us do, be sure to watch for heat stress. Those we grow on wood that we keep in a covered orchid house are showing signs of needing more attention: leaves are puckering and some leaves are beginning to turn yellow. The usual watering schedule of 2 or 3 times a week needs to be increased. So today we moved some to the back of the Vanda trellis, which is watered more frequently, and put others in our slightly cooler Bulbophyllum/Paphiopedilum/aroid house, which also is watered more often.

The American Orchid Society has a good article online about heat stress by Susan Jones. Here is a good tip from her: "A  simple rule of thumb is that an orchid’s need for water increases and decreases with the ambient temperature, so water thoroughly and more frequently during higher temperatures. Most mounted plants and those in baskets, especially vandaceous orchids and other genera grown with little or no media, will benefit from daily watering in warmer weather."

Here are heat stressed Cattleya leaves:

Wilt may be a sign that your plant needs more water in high heat.

As summer cranks up, we also mist our vandas for a short time about 2 in the afternoon just to cool the leaves. Dendrobiums can be watered daily now.

What not to overwater? Tolumnias, orchids we once called equitant oncidiums.