I like Vandas. When I started up again growing orchids a couple of years ago, I figured that, since I live in a warm place, I might be able to grow them. But I also read they need very high humidity. I read the roots should get very wet every morning, then dry by nightfall, or they would definitely rot.
Those who have ADD, or are very old and don't have much time left, can skip the rest of this post and read the executive summary: Water Vandas more than you can now imagine. Fertilize Vandas more than you can now imagine. Vandas do not need high humidity. They need to be watered enough to compensate for low humidity.
I came across a sticky thread here on Orchid Board about
growing Vandas in glass vases.
So! I bought some seedlings and put them in glass vases. I used a spray bottle to get the roots really, really wet each morning. I sprayed and sprayed until the roots turned completely green. I kept them inside an aquarium with a glass top, lighted them with CFL bulbs, and kept a glass of water inside to keep the humidity up.
My seedlngs dwindled. Their roots died back from the tips. Their leaves became finely wrinkled, then shriveled, then some of them died. How could this be? I was wetting their roots every morning. I observed the roots were white and dry within an hour. So I began spraying them with water morning and evening. They were, again, dry within an hour. I used KelpMax on them. They grew new roots immediately, and these new roots soon died back from the tips. The seedlings didn't look quite as unhappy as with one wetting a day, but they still barely survived, and hardly grew.
I began soaking them in water for a half hour every few days, still spraying the roots once or twice a day. They looked a little better. I tried leaving water in one of the containers, with the roots just touching the water. Those roots began rotting back in a few days, so I stopped doing that.
Over the last year I've been steadily increasing the proportion of time the roots spend soaking. I'm now up to overnight soaks almost every night. My plants finally look healthy and happy.
Kim / Fairorchids has posted about how he and his dad grow/grew Vandas in containers, and how important it is to keep their roots moist. I have never been able to keep them alive in pots. Bare-root works for me.
I did some thinking. In places like Florida and Thailand, with humidity so high mildew seems to grow on chrome bumpers, the roots take hours and hours to dry out after a good morning soaking. The plants are absorbing water the whole time. In my conditions, the roots are dry within an hour. My plants don't have time to absorb enough water unless I soak them.
I read a lot here about people having trouble with Vandas. Not many people in my orchid society will even try to grow them; they've failed in the past. We all say something like, "But I get the roots wet almost every day." Then we show photos of a plant that is obviously not getting enough water.
The take-home is that we water our plants in order to give them the water they need, not to match what we're told to do in books. I don't live in swampy Florida. Others here are trying to grow orchids indoors in the winter, with artificial heating. We need to keep the roots on our Vandas wet for a much longer period of time than people do in Florida.
I've also learned that root growth in my Vandas is a function of how wet they are. The wetter I keep the roots, the more root growth, with or without KelpMax. It doesn't hurt my Vandas at all to soak in water for 24 hours.
Leaf growth is a function of how much I fertilize them. More fertilizer is better for Vandas. I fertilize by filling my vases with fertilizer solution, then letting the plants soak overnight. However, if any roots are above the water level when soaking in a fertilizer solution, solute-laden water will evaporate from the above-water roots, leaving behind salts, and the roots will burn. If you soak in fertilizer solution, as I do, make sure the water level is well above the highest roots.
I have read magnesium deficiency is common in Vandas. I usually add Epsom salts to my soaking water when I am not fertilizing, a teaspoon / 5ml powder per gallon / 3.78 liters of water. The plants have crusts of salt at the leaf bases after a good overnight soak. This shows how much water they are transpiring. This has never harmed my plants, as far as I can tell. I rinse off the salt crusts.
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