Important!! Calcium Deficiency
 

All,

Over the past 2-3 years, I've had to re-learn how to grow my orchids indoors for either all or part of the year. The plants inside get RO water, so long story short, I've come to realize that many of my 'chids have been suffering from calcium deficiency. I've been adding Ca/Mg to my watering regime since I got to Texas, but it was not enough. In the past month or so, I've taken steps to increase my Ca dosage, but I won't see results until the end of the next growing season in many of my plants. :((

Its a VERY avoidable problem that masks itself as rot on new growths. Here is a link to pictures of Ca deficiency in orchids:
Images of Calcium Deficiency on Orchids

Here is a great written description of Ca deficiency in orchids, including how to fix the problem and why it happens: http://rockhamptonorchidsociety.com....Deficiency.pdf

I figured this is something that everyone on OB should read!!

I agree with you 100% but, the problem for orchids is that they are unable to adequately limit their calcium uptake, and will absorb too much of it when available, resulting in cellular pH too high. Some orchids also have difficulties absorbing Fe, Mn, Cu, or Zn, which is more tightly held in alkaline media, another reason why they thrive in low pH media.

Can you describe the effects of cellular pH being too high, due to excessive calcium?

For the most part, epiphytic orchids get the majority of their nutrients from the solutions applied (rainfall cascading through the forest canopy in the wild), and not from the substrate.

Nexogen, where did you get this information that orchids can take up too much calcium? I haven't read that before.

Some topics have a tendency to go round and round with no end in sight..... In the end, noone ever agrees. Just an observation.

:badh:

Steve, I have been pretty happy using gypsum and Epsom salts (Ca and Mg sulfates, dissolved 1 tsp/gal). These provide sulfur also. I use this as a stock solution, add several ounces to a gallon of water when I water.

There are other formulations that are fine for providing Ca and Mg, but mine seems to help ward off diseases and is fairly inexpensive.

Calcium deficiency has been a subject of discussion here many times. The importance of additional Ca-support cannot be commented too often. Thanks for the useful links, which also include illustrative pictures.
Rainwater does not contain Calcium. To my knowledge in nature the binding and allocation of calcium is accomplished by complex biological crusts.

Thanks for the PSA, Steve. I've started seeing these symptoms on some of my potted catts, since I've reduced fertilizers to about 20 ppm N. The problem is, the Ca and Mg in those fertilizers are formulated for dosages of 100+ ppm N, so obviously I need to supplement.

A question for those who use the same watering can or sprayer for all their orchids - how do you deal with phrags, which wouldn't appreciate heavy supplementation?

I don't buy that, Alla.

Fertilizer formulations are designed to provide the nutrients as specific ratios to the nitrogen, so no matter what the concentration, the ratio remains constant.

If you lower the concentration, you need to increase the frequency of application, so that the proper mass of nutrients are applied per unit time.

I feed at about 35 ppm N, and am not experiencing any signs of deficiency. I feed about every 2-3 days, depending upon the amount of sunlight and temperature.

I'm also curious about a source for this info since I've heard that its pretty tough for orchids to OD on Ca/Mg. If I remember correctly, I believe Alan Koch at Gold Country Orchids says in his lecture that lots of Ca/Mg is really good for epiphytic orchids.

Yes, I figured if someone who has been growing orchids for a loooooong time like myself overlooks such a simple task as Calcium supplementation, then there are probably many more that do as well.

I know Phrags don't like too much fertilizer, but I wonder if Ca is the same?