Orchid Culture - Questions & Answers from This Month

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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!
 
Green Blotches on Phal Leaf

Green Blotches on Phal Leaf

Q. Are the green blotches on the phal leaf something I should be concerned with, they are more pronounced on the keiki than the mother plant. The plants were moved into the greenhouse when cool weather arrived.
A. My best guess would be some cold water damage, either from overnight condensation dripping on the leaves or cold water from the tap. Check the temperature of the water coming out of the hose and see how close to 70F it is, the water should be within 5 to 10 degrees of the air temperature. The keiki leaves are likely more tender than the Mom's leaves, and more sensitive to cold water damage that can cause mesophyll cell collapse.   (Feb-21)
 
 
Pool Algaecide Strengths

Pool Algaecide Strengths

Q. I have a question regarding pool algaecide versus Physan. Is the product in the photo appropriate and what rate per gal should I use?
A. Physan, which contains 20% quaternary ammonium compounds, recommends 1 tsp/gal as a spray. Your product appears to contain 30%, so you would use 2/3 strength, or 2/3 tsp/gal.   (Feb-21)
 
 
Leaf Damage on Phalaenopsis

Leaf Damage on Phalaenopsis

Q. This phal was with all my others on the north face of a wooden fence. Any ideas what caused this damage?
A. My guess would be the new tender leaves were damaged somehow while they were forming and the scars simply enlarged as the leaves got larger. Perhaps it was mechanical damage, or perhaps water in the crown. The other leaves look great. (Feb-21)