Is this pelargonium, e.g. the pom-pom type flowers held high on flower stalks above scalloped foliage ?

I suspect your pelargoniums either have been transplanted in cool soil and they are not like it, or that your soil has a very strong deficiency of phosphorous (test soil pH first). How were the roots when planted ?

My first thought was cool nights, like in the 40's or 50's. I've had them do that in Spring and Fall when we got those cool nights. Some kind of stress causing this. If it's the cool nights or soil, they'll recover when it warms up.

Kat

Yes, we have had some very cool nights, as cold as mid 40's. The cool nights sounds like it could be the cuplrit. As mentioned in my previous post, the geraniums are growing and have nice big heads, but the maroon edges had me stumped, since the plant looked fine otherwise.

Yes, KDJ, these are the large pom pom types with large flowers and scalloped edges.

Thanks for your input. Anyone else notice this problem?

I had this problem some years ago. Turned out to be a magnesium deficiency.

Here's what one expert says:

"I'm seeing geraniums with red lower leaf margins, which progress to interveinal chlorosis. There could be several causes of these symptoms (which makes accurate diagnosis difficult when you only have symptoms to work with) including cold temperatures, holding the plants very dry for a long period, root problems and magnesium deficiency. The only way to confirm magnesium deficiency is by foliar or media analysis. But if you don't have magnesium in your water, don't have dolomitic lime in the media, aren't applying a fertilizer incorporating magnesium, and feeding predominately calcium and potassium, the problem probably is magnesium deficiency. Even if you have magnesium in the media, high levels of calcium and potassium can interfere with magnesium uptake and the plant shows magnesium deficiency symptoms.

Because of this interaction, you need to look at the balance between these three nutrients. There should be adequate uptake of magnesium when the percent of total soluble salts (saturated paste media analysis technique) for magnesium is above 4% with calcium between 14 to 16% and potassium between 11 and 13%. One application of Epsom salts at 8 to 16 ounces per 100 gallons will usually bring the nutrient balance back into line. Don't over-apply magnesium because high levels can interfere with calcium and potassium uptake, although it would be rare. Remember by the time you see symptoms, the plants have lost growth and quality that they won't regain. Don't guess. Media test."

-Michigan State University