Cattleya calcium levels

[Missanna]

Thanks for clearing this all up. I wish they would also list the actual percentages of the ingredients that added up to 100, but I do really like that some labels list how many ppm is in a certain volume. My fertilizer has that and I am really thankful for them making it so easy. I think 1/4 tsp is 50ppm N or something like that.

Anyway, I know I can't ask for brands or specific stores, but I have a small collection (50) so fertilizer lasts a really long time and I don't need a huge 25 or even 5 lb bag of calcium nitrate (from fertilizer places). Is there some KIND of place where I can buy a smallish jar of this? I read that it is used in medicine, so I called a local compounding pharmacy but they didn't have any. I use Epsom in baths all the time, so it's fine to have a big bag of that, but I don't think calcium nitrate has any uses around the house. I had soaked my one plant in a dissolved calcium pill but realized that the ppm of actual calcium in there is unknown because of all the binders etc in the pills. I don't want to use gypsum for the same reasons- also it's dirty and takes forever to dissolve. I think it would be a good idea to add some extra cal mag in summer when temps are high. I am not able to get temps below 68 so far, even next to my humidifier. Nights are still around 70, so opening windows would be useless.

[Catt Mandu]

I have seen Ca nitrate in medium-sized bags (maybe 10 pounds) at stores specifically for gardening (as opposed to big box stores with a garden center). If you have friends that raise orchids, maybe you can split a bag.

Another thing to consider - I talk about using gypsum to provide Ca. Well, plaster of Paris is just gypsum with the water driven off by heat. I have enough pelleted gypsum to last me a while, but next time I run out, I'm just going to use plaster of Paris (note: this is different from "lime plaster"). Plaster of Paris is often sold in boxes or cartons of a few pounds each in hobby stores. I would still dissolve plaster of Paris 1 teaspoon per gallon of water.

[raybark]

Just an editorial comment: why worry so much about adding stuff like gypsum, plaster, calcium nitrate, magnesium sulfate, etc., when one can simply purchase a complete fertilizer and be done with it? While a knowledgeable person might like the control provided by the "do-it-yourself" approach, to the average grower, manipulating the nutrient formula can be the fast way to disaster.

Shifting gears...

Missanna, while not particularly precise, because ppm is a weight-per-weight measurement, teaspoons are volumetric, and not all fertilizers have the same bulk density, a pretty reasonable rule-of-thumb for estimating the ppm N for ANY fertilizer is to simply divide the following numbers by the %N on the label:

2 - 25 ppm N
4 - 50
6 - 75
8 - 100
10 - 125
12 - 150

So, in the case of K-Lite at 12-1-1, if you want 50 ppm N, it's 4/12 = 1/3 teaspoon per gallon. For Dyna-Gro "Grow" formula at 7-9-5, you'd need 4/7 = 0.57 teaspoon for the same level (for convenience, I'd go with 1/2, giving me 44 ppm N).

If you want to know more details on the contribution of other ingredients, a lot of folks use the calculators here.

[Catt Mandu]

Well, I think "the fast way to disaster" is a little over-stating things. I think that anyone knowledgeable enough to be concerned about fertilizer beyond the N-P-K can figure this out.

There is a benefit to providing a fertilizer that does include sufficient Ca and Mg, as well as balanced N-P-K and other nutrients, but taking the do-it-yourself approach can be just as easy and somewhat cheaper.

[Missanna]

Re: editorial comment:

Yes, in general, I believe that a balanced fertilizer is the way to go when you have a normal, healthy plant. The original question was to help me figure out a good dosage to remedy a deficiency. If, for example, under my conditions for a normal plant, the correct amount of calcium is 50ppm once a week, then perhaps adding an extra 25-75 ppm for the newly acquired deficient plants would be a good place to start. Since the rot was setting in rapidly, I would have gone ahead and given one big emergency dose immediately to one of them and then over the next month or so, given a slightly higher amount each week to both and see which one does better.

Catt- for my smallish collection, a 10 pound bag would last me five lifetimes. I don't know any other orchid growers in my area to share with- the closest OS is 2.5 hours away from me. I think a small amount can be purchased from chemical supply places or similar. Thanks for the dosage for the plaster and for noting the distinction between plaster of Paris and lime plaster.

Also, a lot of people find that at certain times of the year or for certain kinds of orchids, their complete and balanced fertilizer just isn't adequate and a supplement is needed which seems to be the case here. For the benefit of people who may run into this problem in the future, I wanted to find out a reasonable dosage and decided to come to the forums to have this discussion so we can all be better growers.