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yellowing leaf on phlox perennial #879049

Asked July 27, 2024, 6:07 PM EDT

My phlox plant was developing a mottled yellowish leaf earlier this summer in a hot, dry weather pattern. Now it seems to be changing over to the normal green. Does this have anything to do with the hot weather or is it related to disease?

Jefferson County Colorado

Expert Response

Good morning!

If you could send over a few photos of what you are seeing I can help out more! It could be plant stress, nutrient deficiency or a disease depending on what the leaf looks like.

Thanks!

Rachel

An Ask Extension Expert Replied July 30, 2024, 9:09 AM EDT
Hi Rachel,
Here are 3 photos of the plant with the stressed leaf and with the normal leaf.  
Hope this helps.
Suzanne
From: ask=<personal data hidden> <ask=<personal data hidden>> on behalf of Ask Extension <<personal data hidden>>
Sent: Tuesday, July 30, 2024 7:10 AM
To: stealela <<personal data hidden>>
Subject: Re: yellowing leaf on phlox perennial (#0148967)
 
The Question Asker Replied July 30, 2024, 4:15 PM EDT

Thank you for sending over those photos! 

That looks like a phosphorus deficiency - phosphorus deficiencies show up in the older leaves and does not affect the new growth which is why you see the nice green on the top of the plant. 

Have you fertilized at all recently? I would suggest using a phosphorus rich fertilizer. Bone meal is a great source of phosphorus. When you are looking at fertilizers there are three numbers on them (looks like 3-5-3) those number stand for the ratio of nitrogen, phosphorus and potassium in the fertilizer. I would grab a fertilizer that has a higher middle number (phosphorus) that the other two numbers. 

Please let me know if you have any other questions and thanks for reaching out!

Rachel

An Ask Extension Expert Replied August 01, 2024, 11:27 AM EDT

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