Leaf splits along the midline in thick-leafed orchids like Cattleyas and Phalaenopsis are almost always caused by insufficient watering. Some individual plants use more water than other, very similar plants. This would also lead to poor flowering.
I believe "weakly weekly" fertilizing doesn't work in warmer areas where orchids grow faster than they do in cold northern climates. I've read "weakly weekly" for years but my plants most definitely grow faster when I fertilize them heavily. On April 9
I posted some Phal. information from a professional grower in our orchid society. He uses MSU fertilizer at 1 teaspoon per gallon, once a week, on all his Phals. Here is a quote from one of his articles:
Quote:
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The often recommended "weakly weekly" fertilizer regimen produces substandard results in Phals.
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He also said not to give Phals too much light or their flowering will be diminished. At your latitude sun should not fall on the leaves. Medium to bright shade is best for Phal. flowering.
Vandas are heavy feeders. Martin Motes of Motes Orchids has written that he waters bare-root Vandas every day, sometimes twice per day. He fertilizes every fifth watering with MSU fertilizer at 1 Tablespoon per gallon of water. In the past he used a 20-20-20 fertilizer at the same dilution. This is very much more than needed by most other orchids. Your plants are not bare-root, but I would fertilize heavily at every 5th watering.
After fertilizing the Vandas you could dilute the remaining fertilizer water by adding 2 parts of water to 1 part of fertilizer to get 1 teaspoon per gallon, and use that on your Phals. So if you mixed up a gallon, and had a half gallon remaining after fertilizing the Vandas, you could add two half gallons of water to the half gallon of 1 Tbs per gallon solution to get a final concentration of 1 tsp per gallon, since there are 3 teaspoons in a Tablespoon.
I find Oncidiums do well with 1/2 teaspoon per gallon. After fertilizing your Phals, if there is any left, you can cut it 1 part fertilizer to 1 part water to get 1/2 teaspoon per gallon, for your Oncs.
Leaf vertical splits
with some Oncs and a couple of yearling vandas that are growing very slow and after a yr or two have not spiked yet, however the vandas still seem healthy in the east window. When I remember I about twice a month double the weakly weak watering. All my plants except a babied no root Onc with division of three rootless pseudobulbs. the mother one is adding new roots in LECA with sphagnum on top.
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