Calcium/Magnesium supplements - how to?

[stompy]

One of my Cattleyas is showing CA/Mg deficiency in semi hydro. The plant is otherwise fine with decent root growth (not as good as some of my others). However I have noticed that the new growths are gradually turning black. It's not bacterial rot as far as I can see

Reading on this forum it looks like its Ca/Mg deficiency. I use RO water and Dynagro which has 2% Ca and 0.5% Mg to feed. Should I add a supplement like

Amazon.com : General Hydroponics CALiMAGic Quart : Garden & Outdoor

and incorporate it in to my feeding schedule? Should I do it for all my plants?

How do you guys supplement Ca/Mg in semihydro?

[Ray]

Are the growth fronts turning black from the growing tip and progressing downward, or is it starting elsewhere on them? If it's a calcium deficiency, it will happen when the growths are emerging, starting at the growth tip.

How much, how often, and which Dyna-Gro formula are you feeding?

ALL plants need calcium on a regular basis, and I would think the D-G product could do that.

[stompy]

Originally Posted by Ray

Are the growth fronts turning black from the growing tip and progressing downward, or is it starting elsewhere on them? If it's a calcium deficiency, it will happen when the growths are emerging, starting at the growth tip.

How much, how often, and which Dyna-Gro formula are you feeding?

ALL plants need calcium on a regular basis, and I would think the D-G product could do that.

It happens when the growths are emerging, starting at the growth tip. It has happened on the 2 new growths and only starts once the groth is about 2-3 inches long. The rest of the plant looks healthy and its producing roots as normal. I use RO water (that I buy at the store) and flush each time before watering. I feed my plants weekly with 1.5mL DynaGro/1L water. This is the DynaGro

Amazon.com : Dyna-Gro ORC-008 8 oz Orchid-Pro Liquid Plant Food 7-8-6, White : Fertilizers : Garden & Outdoor

Really looks like necrosis and not a bacterial problem. I would have expected a bacterial issue to spread quickly. This has happened very slowly over the course of 2 months. I excised the effected leaf tips last night and treated with cinnamon. I just don't don't want to loose the next growth the plant makes. The rest of my plants seem fine but I'm worried they are effected too

---------- Post added at 10:25 AM ---------- Previous post was at 10:20 AM ----------

I bought the CaliMagic supplement last night. Should I use it only on the one plant or my entire stock? Is there such a thing as excess Ca/Mg?

[Ray]

Well that certainly sounds like a calcium deficiency, but that formula applied at that rate (about 105 ppm N) should be providing about 30 ppm Ca. For a comparison, I feed 25 ppm N K-Lite and that provides about 20 ppm Ca. I do feed at least twice as often though, usually 3 times a week, so my supply is 1) steadier, and 2) greater in total mass.

Calcium is not easily translocated within plant tissue; once it has been absorbed, it pretty much stays put, so if there is new growth happening, it needs a steady supply.

It may be that you just need to "up" the Ca a bit, but I'd experiment first by adding it to your D-G solution to see if it reacts at all (i.e., does it form a precipitate).

Magnesium is not an issue in this, by the way, as it IS easily moved around withing plants, from old- to newly-growing tissue. If you suspect a shortage, a tablespoon of Epsom Salts per gallon, applied monthly with the fertilizer, is more than enough.

Yes, you can provide too much calcium. Too much can actually prevent the uptake of other nutrient ions.

The Calimagic label says 1 ml/L, which will add about 10 ppm N, 50 ppm Ca, and 15 ppm Mg, so maybe that's all you need!

[stompy]

Originally Posted by Ray

Well that certainly sounds like a calcium deficiency, but that formula applied at that rate (about 105 ppm N) should be providing about 30 ppm Ca. For a comparison, I feed 25 ppm N K-Lite and that provides about 20 ppm Ca. I do feed at least twice as often though, usually 3 times a week, so my supply is 1) steadier, and 2) greater in total mass.

Calcium is not easily translocated within plant tissue; once it has been absorbed, it pretty much stays put, so if there is new growth happening, it needs a steady supply.

It may be that you just need to "up" the Ca a bit, but I'd experiment first by adding it to your D-G solution to see if it reacts at all (i.e., does it form a precipitate).

Magnesium is not an issue in this, by the way, as it IS easily moved around withing plants, from old- to newly-growing tissue. If you suspect a shortage, a tablespoon of Epsom Salts per gallon, applied monthly with the fertilizer, is more than enough.

Yes, you can provide too much calcium. Too much can actually prevent the uptake of other nutrient ions.

The Calimagic label says 1 ml/L, which will add about 10 ppm N, 50 ppm Ca, and 15 ppm Mg, so maybe that's all you need!

Thanks Ray! Informative and clear as always. One big reason I got back in to growing orchids was semi hydro. I just didn't think I could grow them with my schedule in my small apartment. All my plants are in semihydro so it has been a completely new experience for me.

[bogdan]

I used to have this problem with plants in s/h before switching to the new Rain Mix formula from Akerne (that's as close to the MSU that can be found in Europe). I have a Cattleya maxima which blackened every new growth from the tip down and, after cutting the black portion and dusting with cinnamon and switching to another brand of LECA and using the Rain Mix, the plant produced this year already 2 growths in succesion from the half-cut old growth, 3 times as big. Both of them have sheats, maybe it will eventually grow something in them!

LE: forgot to mention that I use RO water and once a month flush with tap water. It's very chalky, so that's one additional source of calcium.
I actually don't even know why we are using so much RO water with them.

[Ray]

Originally Posted by bogdan

forgot to mention that I use RO water and once a month flush with tap water. It's very chalky, so that's one additional source of calcium.

Adding it once a month is inadequate, because as the plant grows it must have a ready supply. Most nutrients can be taken from old growth and moved to new, but calcium isn't one of those.

I actually don't even know why we are using so much RO water with them.

Because they plants have evolved to thrive on water with low dissolved solids content. If you can find the right balance of low-TDS water while providing sufficient nutrition (and that's not much) in the right proportions, many of your issues will vanish.

[bogdan]

Originally Posted by Ray

Adding it once a month is inadequate, because as the plant grows it must have a ready supply. Most nutrients can be taken from old growth and moved to new, but calcium isn't one of those

Adding tap water, even once a month, shouldn't be necessary while using a fertilizer with plenty of calcium in it, which I do use, but I figured it might be cheaper to flush thoroughly with tap water instead of the regular RO water.
However, I saw a black tip beginning on a new growth (planted 2 months ago in Orchiata with its added dolomite, go figure) so it seems that the daily 31 degrees under lights and the increased growth rate cannot keep up with the orchids' calcium needs.

I had the dilemma regarding tap water vs RO after I received some orchids with what appears to be heavy carbonate deposits on the leaves, so that greenhouse either has only tap water supply and overhead irrigation or the grower sprays the plants with calcium containing formulas (which I gather from this forum to be ineffective). So, instead of buying all sorts of additives, I will try first to use more tap water, as mine has no chlorine added, albeit quite a lot of iron particles (rust?).