What is this?

[dfollett]

Originally Posted by KarenO

may not be strictly a deficiency of iron but rather an uptake issue caused by too wet, high soil ph, excessive phosphous etc. google iron chlorosis

KarenO

I had a similar problem with only a few plants in a flat showing severe yellowing. Karen's list mentions what I have concluded was the cause of my problem - High soil ph.

I add Garden lime to the peat based container mix I use. I recently purchased a new bag of lime. It is very finely powdered rather than the pelletized lime I have used in the past. I add the lime to the mix of peat, bark and perlite then stir it to blend everything. I think the powdered lime adheres to the damp peat it touches first and doesn't blend evenly like the pelletized lime does. That leaves a small portion of the mix (that portion with the limey peat) very high in lime and the rest with no lime. That portion of the mix heavy in lime will be much higher ph than the no-lime mix.

I'm not positive that is the answer to my issue, but that is the conclusion I've come to. Does my conclusion make sense to you gardening pros? That is the only answer I've been able to come up with.