It was mentioned on another site that orchids require calcium. Is this true and if so other than eggshells what is a good source, how much should be used and how often?

All plants require calcium as it is used in the construction of cell walls. Any decent orchid fertilizer should contain it as calcium is one of the macronutrients required for plant growth. If you are still concerned, calcium nitrate can be purchased and applied at a rate of about a half teaspoon per gallon of water. Any deficiency would first be noticed on Cattley type orchids in the warm growing season. Look for brown leaf tips and yellow bands around the pbulbs.

Jim

There are also quite a lot of Phragmipediums which in their natural habitat grow on huge limestone hills. I eat Oysters every so often, boil the shells clean afterwards and add them crushed to the Orchid medium. Phrag kovachii, besseae, schlimii and others and their hybrids fall into that group.

Thanks Jim and Ursula. I'll have to take a look at my Better-Gro orchid food

Good point, Ursula. Terrestials bring in an additional factor.

Jim

So, for my Phals, where do I get the calcium additive and how much would I use?

You should be able to find calcium nitrate in a good nursery or perhaps a hardware store. It is not difficult to find. Like I said before, use about a half teaspoon per gallon of water.

Jim

Thanks Jim and I just add that to my bark during my regular watering/fertilizing schedule correct?

Calcium is not water soluble. So for your plants to absorb calcium, the nitrate part is important. Look for calcium nitrate.

I would like to hear why you think your Phals are suffering from calcium deficiency to the extent that you would have to take this action. It would not be a common occurrence.

Jim

I don't know if they are not Jim, I'm not an expert on any type of orchid but you said to me in an earlier post in this thread:

"All plants require calcium as it is used in the construction of cell walls. Any decent orchid fertilizer should contain it as calcium is one of the macronutrients "

and after looking at the contents of the Better-Gro orchid food I use and not seeing calcium nitrate listed is when I continued to ask my questions. Now, I have no earthly idea as to how to tell if they are suffering from calcium deficiency.

Read this - its interesting and may answer the question:

http://staugorchidsociety.org/...

DaisyI said:Read this - its interesting and may answer the question:

http://staugorchidsociety.org/...

Thanks Daisy, I have none of those symptoms but I can see that misting my Phals with calcium nitrate would not harm them and could only help especially since I'm using nothing but distilled water. Currently I'm misting twice daily with distilled water and this - http://www.supplysource.com/Po... which I've mixed 1/2tsp into a gal of distilled water. Now is the calcium nitrate a weekly or daily application to the foliage? If daily can it just be mixed in with the gal of potassium nitrate? If weekly no big deal I can just mix a separate jug of it and mark a separate spray bottle. I've already ordered some calcium nitrate last night.

Chris, I looked on all my seven (yes, 7 ! ) different fertilizer packages and only one - the MSU formula - has any calcium in it. This may be because it is formulated to be used with R/O water. I'll bet that if you just misted with your tap (hose) water once a week, that would very likely supply all the calcium your plants need. I've never added any calcium supplement to my orchid regime but my automatic mist system uses well water which has plenty.

Please be sure not to "kill them with kindness" here. You do need to let your plants dry out a bit, even though they like high humidity. I'm only using the Potassium nitrate formula once a week on my Vandas (which are heavy feeders) at the moment. Phals are not fast growers or heavy feeders. I'd advise you ease up on the misting and feeding, and just let them dry out at least every second day.

You can keep the humidity up in your greenhouse without misting the plants - just spray the hose around on the floor, walls, and other surrounding stuff. Clay pots absorb and release moisture, so if you have any plants in clay, spray the outsides of the pots and they will help with the humidity. If that's not enough, hang some old towels in there, and wet them down daily.

I also hang my laundry to dry on hangers around the plants when I have them in the house - usually that's in cold weather which is also dry weather here. Just tumble in the dryer for about 10 minutes then hang up, and distribute. Saves on electricity and humidifies the area as well! A win/win!

I was under the impression that most water in TX is pretty hard and calcium is usually the cause of the hard water.

Right, but Chris has been watering and misting his plants with distilled water for a couple of months because he was getting so much hard water deposit on the leaves.

I think his plants probably have plenty of calcium left over from all that.

Elaine, when I first started asking questions here about my Phals if you remember how much white coating was on the leaves? That's because I was misting with tap water. Our tap water has a pH lever of 7.8 -> 8.3 which I was told somewhere on here that it's too high for orchids and that I should use distilled water which is what I've been doing. They only get a light misting twice a day with the potassium nitrate which is mixed 1/2tsp to 1gal of distilled water. They're getting fed/watered every 8 or 9 days with Better-Gro food 1/2tsp per gal of distilled water. Every 4th time they get just water poured through to rinse them out.

I know Chris. The hard water deposits on the leaves of your orchids was most likely a good part made of calcium from your tap water. That's why I'm saying I don't think you need to be buying something to "add" calcium when you have it right there in your tap water. Maybe give them a douse with the hose once a month, for a shot of calcium from the tap water.

The potassium nitrate IS fertilizer too, so you are feeding your Phals very lightly every time you mist them with it. It just sounds to me as if you aren't letting them dry out very much between all the misting and watering you are doing. Try leaving them to dry out at least a couple of days a week and see what happens?

The number one cause of death in orchids is over-watering, remember.

To clarify on the tap water issue, it won't hurt your orchids at all as long as you don't use it on them too often. If you start seeing the white crusty stuff again, ease back on using it. Plenty of calcium - so much that the plant couldn't absorb it and it crusted on the leaves.

My orchids all get watered automatically with my untreated well water, pH 8.2, that has run through miles of limestone caves so it's full of calcium. The Vandas and mounted orchids get it every day. But I also have a large supply of rain water that I rinse my orchids with, and of course they get rained on from the sky periodically, even in this, our "dry" season.

So I don't have any problems with hard water deposits on the leaves. I've bought orchids from well respected growers that have had those deposits on the leaves. The danger is that the stuff will clog the stomata and eventually the leaf will not be able to absorb water and nutrients very well. That takes a long time, and a lot of deposits.

The other problem with high pH water is it often also has too much phosphorus in it as well. Phosphorus blocks the uptake of a bunch of nutrients if there is too much in the water. When I fertilize my orchids I use rain water so there's no phosphorus in it, and the pH is close to neutral. Just like your distilled water.