K Barrett asks: >Martin, so what's your gripe with fertilizing weakly weekly?
Orchids in the wild (at least those growing (epiphytically) really get pretty low levels of fertilizer, and most of their liquid refreshment from rain water. There are those that believe that emulating native conditions is the ideal, and orchids will grow and bloom in the home or in the greenhouse if these conditions are met, so weakly weekly is OK if you just want your plants to survive. But if you really want to get the most out of your orchid plants weakly weekly doesn't cut it. It's all about photosynthesis. The more food and light you give a plant (within limits, of course) the better they will grow, and the better they grow the better they will bloom. It starts with the water. Rain water has a low TDS level, so there is worry about burning the roots with too much TDS in the water. Then we add fertilizer; more TDS. Actually, most orchids can tolerate a surprising amount of TDS (not all are equal in this respect). Indeed, controlled experiments by Dr. Wang suggest an EC of 2000 as being the limit for Phalaenopsis. He finds a nitrogen level of 200 ppm applied at every watering is optimal for Phalaenopsis. But that is only one genus. I have grown a few thousand different orchid species in hundreds of genera and have come to the conclusion that for me 150 ppm of nitrogen (1,000 ppm of dissolved solids) applied at least twice a week works very well for me. Even my Pleurothallids grow well, though I believe they would do better if they I grew them cooler. Of course to make use of this 'food' the plants need light, the more the better if you don't burn the leaves and if they have a dark period to fix carbon dioxide (the CAM plants, that is). I have been growing under wide spectrum HID lamps for the last year (I moved to a condo and sold my house, greenhouse included) on 16 hours a day for nine months of the year. The lamps are generally somewhat closer to the plants than recommended. The lamps generate enough heat to keep my plant room warm even on the coldest days in Northern Massachusetts. To keep from burning the leaves I installed a LOT of air movement. No burnt leaves. How about water quality? I believe that when water poses problems it's usually not the TDS that causes them but something in the water. When I first started growing in Massachusetts in the late 1970's my water was low in sodium. Over the years the sodium level rose fairly dramatically and I began to see brown tips on my Draculas. I postulate that sodium is the bad actor, not the dissolved solids level, and when I moved to my condo I put in an RO system. I add 30 ppm of calcium to my water as calcium nitrate (ca 160 ppm TDS) to make up for what the RO system has removed for my daily watering (the high level of air movement makes the plants dry out more rapidly than they did when I had a greenhouse). And for my fertilizer I add 150 ppm of Peters 15-16-17 Peat Lite Special, which I supplement with 20 ppm of magnesium in the form of Epsom salts. If one is not careful to flush thoroughly when watering and/or fertilizing the fertilizer can build up and exceed what may be tolerated by the plants. See the excellent article by Fred Bergman in the May issue of Orchids. Weakly weekly is largely a product of Communal Reinforcement. From the Skeptoc's Dictionary (http://www.skepdic.com/comreinf.html) >Communal reinforcement is the process by which a claim becomes a >strong belief through repeated assertion by members of a >community. The process is independent of whether the claim has been >properly researched or is supported by empirical data significant >enough to warrant belief by reasonable people. Often, the mass media >contribute to the process by uncritically supporting the claims. >More often, however, the mass media provide tacit support for >untested and unsupported claims by saying nothing skeptical about >even the most outlandish of claims. A caveat: The above discussion is a simplification of a complex subject. Martin
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