Splotchy Leaves on Laelia tenebrosa

[Rhonda Svoboda]

I am not sure what's going on but a few of my orchids have developed splotchy leaves. They've been under grow lights all winter. Could this be because of uneven lighting?

[rbarata]

Read this, especially Calcium and Magnesium deficiency.

[Rhonda Svoboda]

Awesome!! I'll try it

[Ray]

Rhonda,

Before you go throwing additives at the plant, what water supply do you use and what fertilizer formula, concentration, and frequency have you been applying it?

[Rhonda Svoboda]

I use Better Grow Orchid Plus. I cycle between bloom booster and the regular formula. I have city water so its probably alkaline, I am guessing 7.5ph which is pretty standard in West MI.

---------- Post added at 03:00 PM ---------- Previous post was at 02:55 PM ----------

Also- if I do have a Mag/Cal deficiency would it hurt to add it to all of my orchids once a month? I have to water at least 3 times a week. Perhaps the fertilizer is being flushed out to fast to maintain the required levels?
Should I fertilize more than twice a month?

[estación seca]

Alkalinity sometimes, but not always, may reflect how much mineral content is in the water. Some city water has a lot of calcium; other doesn't. If you let water dry on your windows, are there distinct mineral stains? If so, your tap water probably has plenty of calcium if the pH is appropriate.

You aren't watering plants with softened water, are you? That takes calcium out of the water and replaces it with sodium. It's not good for plants, and it's not good to drink.

As Ray says, if you have enough calcium and magnesium in your water, you won't need to supplement. But we suspect you don't.

City water departments in the US are required to publish water quality reports annually. Mine lists the mineral content and pH of my water. I searched for "Grand Rapids water quality report" and found this:
Water System

Scrolling down, under Water Quality, I found a link to the water quality report. Unfortunately it only shows levels of toxic substances and contaminants, not normal minerals, not pH. I haven't seen this situation before.

So I would call your water department and ask for information on how much calcium and magnesium is in your water.

It can take weeks to replenish low calcium or magnesium in plants. There is a limit to how much they can take up with a single watering, so it doesn't make sense to give high doses regularly. Low doses every watering makes more sense.

Edit: Better Gro does't list the formulation on their Web site. Home Depot has a photo on their site that can be enlarged to show the formulation. It's 20-14-13 with micronutrients and 1% magnesium.

The Orchid Plus probably has enough magnesium for ongoing use, if your pH is proper. A magnesium-deficient orchid would get better faster if you use more. Get some Epson salts from the drug store. Add 1 teaspoon/5ml of powder to 1 gallon/3.78 liters of water. You can mix magnesium with the rest of your fertilizer.

Better-Gro Orchid Plus doesn't have any calcium. If your water lacks calcium, you definitely need to use a calcium supplement. I don't know how much calcium is in Lake Michigan, nor how much is in your ground water. You need to call your water company and find out. Don't mix the calcium supplement with other fertilizers. The calcium can precipitate out and not get to your plants. If your water company won't tell you, consider paying for a water analysis from a local lab.

I don't need a cal-mag supplement because my water has a lot of each. Adjusting the pH is all I need to do. But people do need to find out whether they have enough in their water, and add supplements if they don't.

[Ray]

Rhonda - what are the fertilizer formulas, and how much do you mix per gallon?

[Rhonda Svoboda]

So I've some homework to do. Should I add some lime too? Or just try the Epsom salts?

[estación seca]

Lime provides calcium, but it's hard to predict how much. You would also need to be very careful about the pH of your solution; it could wind up very high, and damage your plants. I would get a specific calcium or calcium-magnesium supplement. I don't have any brand recommendations because I don't need/use them.

Epsom salts contain only magnesium and sulfur, not calcium. You would need to use Epsom salts and a calcium supplement.