[jerrymeola]

Cynthia,

Calcium and magnesium are critical for all plants not just orchids. Here in Florida the manufacturers add it to all the fertilizer mixes. This is not always the case it other parts of the country where the chemicals are not flushed from the soil as fast.

My orchid trees (a twenty foot tree with orchid shaped flowers not a real orchid) show the deficiency quickly by becoming lighter green and the veins in the the leaf become very distinct. My Passion Fruit are doing the same this week. Out comes the Epsom salt and the problem is quickly cured.

Bellc

use a balanced fertilizer 20-20-20 rather than the high nitrogen mixes called 'orchid fertilizer' 30-10-10. Buy a good brand with trace elements. You will see magnesium listed on most packages. You can add Epsom salt to your watering routine by watering with a tablespoon per gallon of Epsom salt every second or third month. They do not need a great deal but total lack will harm the plants.

Use fertilizers at 1/2 teaspoon per gallon or less for orchids regardless of the instructions on the package. "Orchid fertilizers" recommend 1/2 teaspoon per gallon but other packages recommend higher amounts depending on what they are recommended to fertilize. All fertilizers are basically the same (trace minerals can vary). You can use any package of fertilizer for orchids if you reduce the strength.

This is a good time to mention slow release fertilizers. For the home hobbyist, it is not necessary to use. Commercial growers often use them to boost growth, and also use injectors in automated watering systems.

If you decide to use a slow release fertilizer use ThemaCote (also called Dynamite) rather than the more common Osmocote. Osmocote is a temperature release fertilizer and ThemaCote is a water release formula. A temperature release fertilizer can add too much to quickly in hot weather.