Orchid Culture - Questions & Answers from This Month
by Sue Bottom, from the St. Augustine Orchid Society Newsletter. Email us with any orchid question. If we can't answer it, we'll find someone who can! Send photographs too!
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Browning Pseudobulb on Cattleya
Q. I noticed this ugly growth in the very middle of my Blc. Goldenzelle. Fortunately, it was on a separate section and I could cut it out nicely. What is it?A. I'd guess that is damage caused by Rhizoctonia solani, often called brown rot. In cattleyas, Rhizoctonia moves slowly from the older to the younger pseudobulbs and moves up the pseudobulb, which turns brown and hard, ultimately becoming husky. The roots on the older, infected parts of the plant die. You've cut away the infected tissue. You may consider repotting the front healthy part of the plant into fresh mix in the spring when you start to see new roots. (Apr-26)
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Yellow Spots on Cattleya Leaves
Q. I have yellow spots on the leaves and at the base of most of the leaves of a Blc. George King "Southern Cross." Likely the yellowing was caused by scale that has since been removed, and the plant treated. There are no obvious signs of scale at this time. Sometimes I see yellowing at the base of leaves on other orchids, when I don't see any scale. I usually swab some isopropyl alcohol around as a precaution. Is it something else? Will these plants ever regain color?A. The affected leaves won't regain their full green color because the scale destroys the chloroplast when they suck the juices from the plant. You'll just have to wait for the new growths to get nice green leaves. Whenever you see chlorotic spotting on the upper surface of the leaf, it is a good practice to look at the leaf underside for signs of scale, that also love to hide in the leaf axil and under the papery sheath surrounding the pseudobulb. (Apr-26)
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Yellow Leaf Tips on Phalaenopsis
Q. Any thoughts on the cause and treatment for the yellowing tip ends of our Moth orchid. Could it be Anthracnose or just poor conditions and watering style. The orchid lives in a large double glazed window, west facing. Plenty of light, shaded by blinds with sometimes but not often bright sun.A. That phal looks very happy and healthy. The one leaf looks almost like it might have gotten sunburned or too cold next to the window. I don't think it's a disease issue. I would probably just take a single edged razor blade and cut off the discolored tissue, then you won't have to look at it any longer. It looks like you're going to get plenty of flowers soon, enjoy them! (Apr-26)