Fertilizing an orchid

[schmiggle]

I've had an Aeranthes ramosa for a little under a year, and while it hasn't died, it's always grown very slowly. Now I know slow growth is normal for orchids, but it still hasnt finished the leaf it had started on when I first got it. Furthermore, it's been growing much more slowly attached to an urn, and my assumption is that the breaking down orchid mix supplied a degree of nutrients. So even though this species is a "fertilize lightly" one, I decided to go for it anyway.

What I'm nervous about is I know that orchids are vulnerable to root burn. I have a 30-10-10 fertilizer (N is 3% ammonia, 27% urea), and it said to dilute half a teaspoon in a gallon of water, which I did. However, it says to water with that mixture once every two weeks. This is fine if you're watering when the soil feels dry, maybe once twice a week. In my case, however, I spray a small amount of liquid on usually twice a day to keep the sphagnum encasing the roots constantly moist. What I've been doing is alternating fertilizer water with regular water, to wash away accumulated salts. My question is, will this give the orchid an appropriate amount of fertilizer? My concern is that either it will be too much, in which case harmful salts will accumulate (the phosphorous and potassium are in salts), or that I'll wash away the fertilizer before it's absorbed, in which case it does nothing. Thoughts?

 

[The Snark]

Thoughts?

Yes. When you get it worked out, let me know. I'm surrounded by several hundred orchid growers, few of which speak English. The ones that speak English each have their own methods and often make their own secret formula fertilizers. And of course, the problem with trial and error is it could take a half year to discover your fertilizer regimen killed the darned thing. Best of luck.

I'll give you one hint. The giant orchid farm down the road waters, automatic misters, 4 to 12 or so times a day (and night). All the waterings contain fertilizer. What fertilizer and what concentration? Unknown. But it can be done.

 

[schmiggle]

If it's helpful to anyone...

I asked this question on another forum, and these are the two main things I came away with.
1. There's a good chance that the reduced growth has nothing to do with fertilizer. The plant is probably still sulking from being mounted, especially since humidity has been much too low. To address the humidity problem, I've decided to use a humidifier in the room (to great effect, by the way--I woke up this morning to mist flowing around my face and reduced visibility in the entire room this is a better long-term solution than I thought). However, even with increased humidity it could continue to sulk for a while, and this is normal and expected.
2. Fertilizer concentrations are much more useful in ppm than strength. Though this hadn't occured to me, it actually makes perfect sense--how else to compare a 20-20-20 fertilizer with a 30-10-10? Even ppm, as calculated simply, is not quite right, because it usually uses volume rather than moles. However, I imagine it should be close enough to work well. The suggestion I got was 30ppm every watering, which would be approximately 1/6 strength. However, I don't want to fertilize every time, because I want to make sure I wash away any salt residue and I water twice a day. Thus, I've decided to use 50ppm every other feeding. I suppose I could dilute further and fertilize more often, but the truth is that with the container sizes I'm using it's hard to dilute more than a certain amount. Perhaps if I put a little more thought into it I could make it work.