Orchid Culture - Questions & Answers from This Month
by Sue Bottom, from the St. Augustine Orchid Society Newsletter.
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Male and Female Flowers on Catasetum
Q. Does the amount of sunlight exposure dictate frequency of male/female flowers on Catasetum plants? And, is it common to have both sex flowers on one flower stalk?
A. Many commercial growers insist that female flowers are produced because of high light conditions. Fred Clarke has a more nuanced opinion, he says the the most vigorously growing plants (which of course require good bright light) are the ones that have female flowers because the plant has to be very healthy to be able to produce seeds during the dormancy period. Taxonomist Francisco Miranda suggests that early in the season, light levels are higher as the tree hosts may not be fully leafed out and the catasetum leaves are not fully formed so they are not shading the plant. You would also think early season female flowers would have greater evolutionary success because they have more of the active growing season to form the seed pods. My experience is that many of the catasetinae form female flowers on the first flowering of the season with more male flowers later in the summer. Is this because I have both time release and Purely O mixed in with the sphagnum moss, so there are lots of nutrients in the early season (which is also the season of the most direct sunlight) and then the fertilizer gets consumed so later in the season (as the sun intensity diminshes) the flowers tend to be more male? In the in-between period, I get both male and female flowers. My experience suggests it's plant vigor plus seasonal bright light that sets the stage for female flowers. It may not be the norm to have both male and female flowers on the same inflorescence, but it is certainly not uncommon.
White Sticky Stuff on Root
Q. As I was enjoying my Vanda plants this weekend, I noticed some of the roots has this white fuzzy looking thing. Not sure what it is, mealybugs maybe? I used a Q-tip dipped in isopropyl alcohol and tried to rub them off. It seems to be attached pretty good so I used a little more effort. The root tip skin came off but the fuzzy stuff is on the skin that came off real tight. Some of the ones attached itself to the other side of another root. It is not easy to scrape them off.
A. This one was over my pay grade, so I turned to the good Dr. Hackney for his thoughts: "It looks like an attempt by the root to attach to something. Not sure exactly what it is called, but epiphytic orchid roots produce a substance which glues them to objects. I suspect this is what it looks like, but I seldom see it in the pot. When I detach some roots from a clay pot they actually pull some of the clay material off. That is what it looks like to me, which fits her description when she tried to remove it."
Black Leaf Tips
Q. This plant of mine has leaves that keep getting yellow from the tip. I removed the affected tips many times but the issue is not solved. Is it because of some micronutrient deficiencies?
A. Nutrient deficiencies are hard to diagnosis, but I don't think that is what is happening. It could be a fungal problem like anthracnose, but if it were anthracnose, you'd see lots of tiny spots (spores) in the dead tissue. My best guess is that it is salt toxicity, and the plant is trying to shed salts from the tissue. Looks like it's potted in coconut husks, and they can be loaded with salt unless you give it three 24 hour soaks and drain the water in between to remove the salts. Some even treat the coco with calcium nitrate to replace the sodium with calcium.