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``Color change on geranium seedlings #875424

Asked July 01, 2024, 6:10 AM EDT

I grow common geraniums from seed on heat under lights for my outdoor flower beds. The seedlings start out a beautiful healthy green color but too often the leaves turn partially red and then, sometimes, a most unattractive orange. I thought I was overwatering them but when I give them barely enough water to stay alive, the color on some the leaves still quite often changes to yellow and orange. Could you please tell me what you think may be causing this to happen?

Arapahoe County Colorado

Expert Response

Hello Doris,
If you could answer a few questions it may help us figure out what is going on with your seedlings. First, please describe how you're watering the seedings and, secondly, are you fertilizing them? If so, when do you begin fertilizing, what type of fertilizer are you using and how often?
Judy K Arapahoe County Master Gardener Replied July 02, 2024, 1:25 PM EDT

Dear Judy,


Thank you for responding to my query. My seedling trays are the type from which one waters from the bottom. I keep watch on the water in the bottom of the trays and the appearance of the soil. If the soil appears to be a little dark, and/or wet, I cut back on the amount of water in the tray. If the soil appears to be drying out, and becoming light in color and weight, I add water to the bottom of the tray.


I begin fertilizing the seedlings when the cotyledons begin to shrivel and dry out and the first real leaves appear. I have been using the recommendation of fertilizer from Miracle Gro of 1/2 teaspoon (the small end of the enclosed scoop) mixed with one gallon of water every two weeks.


The redness begins with the light red circle formation (normal)? And then spreads out over the leaf and later sometimes changes to orange and then yellow on the edges. I would very much appreciate any suggestions regarding how to avoid this from happening.


Many thanks,

Doris Kennedy


The Question Asker Replied July 03, 2024, 7:53 AM EDT
Purpling of the older leaves on a geranium is not an uncommon problem, particularly in our area. It usually indicates the inability of a plant to absorb phosphorus. The leaves will initially turn purple and then fade to a tan or brown, eventually dying. Since Miracle Gro contains phosphorus, I’m wondering if your geraniums are outside overnight when the temperatures are still a little too cold. If nighttime temperatures are lower than 55 degrees, then you may see this change. This could have been a problem, particularly this spring, because the overnight temperatures were low for a long time—even into late June. If you are putting your flats out overnight to acclimate the geraniums, I would suggest you bring them inside until the nighttime temperatures get a little warmer. If your geraniums are in the ground and the temperature of the air and soil are low, you can simply trim off the affected leaves, which are usually the older leaves. Your plants should be ok as the air and soil temperatures warm.
Judy K Arapahoe County Master Gardener Replied July 04, 2024, 10:03 AM EDT

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