I've previously posted my earlier observations to the
Vandas in Glass Vases sticky thread. I'm realizing low-humidity conditions are so different for Vandas that I'm starting this thread. Unless you've lived in a really arid area it's hard to realize just how dry it is compared to coastal areas or temperate moist climates like the US midwest or most of Europe.
In
that post I wrote
Quote:
Originally Posted by estación seca
I think frequent wetting of the roots to prevent drying is more important than relative humidity.
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Now I'm sure of that.
Update on my Vanda seedlings:
They are still in various glass jars, or plastic bottles I cut to make openings large enough to admit roots. When they get bigger I will move them into nicer vases, but now they would just fall to the bottom.
I think growth was better in transparent containers than semi-opaque white plastic, so I've moved some. Also, the narrower the opening, the longer the roots stay hydrated after watering, but the harder it is to squeeze them in.
They are in a northeast window that gets about 3-4 hours of direct sun per day. The room varies from the mid 80s F / upper 20sC at night to mid 90s F / low 30s C in the day. I'm not brave enough to put them outside in the 105+ F / 41C heat. In the winter that room won't go below 50F at night and will be a lot warmer in the day.
The humidity in that room varies from 30% to 60%, higher when it's raining. There are other plants and 2 aquaria in there.
I spray my seedlings' roots at least morning and evening with MSU fertilizer in rainwater. On weekends I spray them more often. I spray the whole collection once, then again, until the roots are dark green. The roots are white again within 15-30 minutes because the humidity is so low.
I started with 1/4 teaspoon / 1.25ml powdered MSU per 1 gallon / 3.78 liters in the spray solution. Also when I started, I would soak the plants for about 4 hours once every 7-10 days for a few hours in this solution of MSU plus 2 teaspoons / 10ml of KelpMax per gallon.
I use a plastic container that holds all of them, and pour in enough solution to cover them almost completely. They take up less vertical space if I lay them flat. I have to be careful not to knock off name tags. After the soak I put them back into their bottles.
Due to time constraints I soak all my seedlings together. I realize this risks spreading diseases but I don't have time to soak them separately. It is so arid here, and the plants dry so fast once out of the soak, there is little risk of fungus. They all came from one source, Mote's Orchids, so if any has anything they likely all have it.
After about 2 months, with twice-daily spraying and weekly soaking for 4 hours, my seedlings looked just OK, and were alive, but I wasn't satisfied. (In the past I've killed Vandas in bark or baskets within a week.) Sometimes my seedlings were a little wrinkled before the next soak. They slowly pushed new leaves. The roots on only a few plants grew a little longer.
Then I read Martin Mote's book on growing Vandas in Florida. This made me realize they are heavy feeders compared to other orchids. Also, they need a lot of water, but can't stay constantly wet nor moist.
I also read a post here by Bud from New York City mentioning he soaks his adult plants in vases for 6 hours, once a week. That's longer than I had been soaking, and seedlings transpire water faster than adult plants. NYC is a lot more humid than Phoenix during warm weather, so my plants would need even more watering than Bud's.
I decided to up the MSU fertilizer to 1/2 teaspoon / 2.5ml powdered MSU fertilizer per gallon in the spray solution and in the soak water. I spray with this fertilizer dilution at every spraying. I am keeping the KelpMax at 2 teaspoons / 10ml per gallon for the soak solution.
I now soak more frequently and for a longer time. I soak them every 3-5 days, depending on my free time. I soak them overnight, 8-12 hours, to avoid missing a day in the sun.
They responded quickly to this new regimen with better growth. They are making loads of new roots. New leaves are pushing out faster, about a centimeter in the last week and a half since making this switch, and most plants are now pushing leaves at this rate. This morning, many plants had new root nubs that weren't there last night when I put them in the soak. Roots with black tips that hadn't grown since arriving are now growing.
Still, within 15-30 minutes of leaving their bath, the roots are white.
The first photo shows the plants after returning to their bottles this morning. For scale, the closest bottle is a 1-quart jar. One plastic bottle on the left is full of solution. I have to soak that plant in the bottle because the roots have grown so much I can't get it out. I will eventually have to cut the plastic. Some of the plants show the spots that I think were due to warm temperatures during shipping. They have had these since arrival.
The second photo shows a new root nub on Ascocentrum curvifolium. The background is a bath towel. This plant came the first week of June with two long roots. They immediately shrank in diameter and turned brown, as I have learned to expect with Ascos here. But the roots still function and the plant continued to grow. With the increased soaking regimen it put out a new root nub on each of the old roots.
I think the key to growing Vandas in low humidity climates is providing enough water. Frequent overnight soaking seems to be the way to go for people who can't water 10 times per day.
Edit: I think my original photos disappeared in the Orchid Board platform update early in 2017. I think I've attached the same first photo as before. The Ascocentrum mentioned in the text above died when I didn't water it enough. I've now killed three Ascocentrum seedlings, all by underwatering. I'm not going to get more of these until I have an automatic spray system set up on a timer.
I bought these plants beginning May 2015 and took these photos in July - August 2015. I'll try to find these same plants and show current photos.
Vandas in Vases in Low Humidity
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