The only time I had geraniums get red leaves was when they were too crowded and wet. Yanked one to find mold on the bottom.
Do you have a picture?

This is common in phosphorus deficiencies, are you fertilizing? Janet

After I thought about it, I also wonder what size pots you have them in 450 geraniums is alot of geraniums for me.

Thanks for the quick response to my problem. These geraniums were repotted in regular geranium pots after they grew true leaves. I have only fertilized 2 0r 3 times. Maybe this is the problem. I will try fertilizing them more. I don't think they have been kept too wet as I let them dry out between waterings and have them in a soilless mix that drains well. No mold on the bottom of the pots. Thanks again for the advice. I am willing to try about anything as this is very disappionting to both me and the kids needing these for their project. Any other suggestions would be appreciated. Prudy

These geranium seeds were planted 1/03/07. They were moved to lights and than to the greenhouse. This is the 3rd year the kids have planted geranium seeds. They've always had such great success before this year. The geraniums were planted to be given as Mothers day gifts from the kids. I do have fish emulsion so will suggest trying this. Also, we'll move them to different soil. Thanks again for your suggestions. Prudy

Red or reddish leaves on geraniums are almost always caused by a trace mineral deficiency (phosphorous as someone mentioned above, or boron). This will often happen earlier or later in the season when temps are cool. If you are having night time temps 55 or below, this will inhibit the absorption of these trace minerals. They are usually present, but the cool prevents the geranium from using them. If you can bump up day and night temps to between 66 and 69, you should see the redness go away. It is also usually most evident on larger, older leaves. Hope this helps.

Mine are turning red too and for sure it is not because of cold, or no food. The entire leaf is turning a bright shade of red. Suggestions? Will post photo later.

petra, I just purchased this one the other day, It's called Velma Cox Geranium maybe thats what you have?
Christine

Same problem here...

I overwinter them in my sunroom but they have been outdoors now for approx a month. Cut back and Replaced with fresh MG potting soli. Forming buds now.

We've had quite a bit of rain lately, not sure if it's that? Or maybe they need to be fed?

I've always removed the leaves in the past when I had one or two, but this one seems to have more than usual.

Thanks in advance.