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Problem with delphiniums #875444

Asked July 01, 2024, 9:22 AM EDT

Hi. I planted my delphiniums last year without problem (full sun, zone 6b). This year, besides having an animal bend the plants and eat the flower buds, a few are turning brown and the leaves are brown on the edges. Is it just a matter of adding fertilizer? Thx

Oakland County Michigan

Expert Response

Hello Lisa,
I don't know if this is a fertilizer problem. If you do fertilize, when was the last time? Do you see any insects on the plants? There are indications of insect damage. Thrips, a small, .04-.08 inch bug, are a common problem of delphinium. 

Have any insecticides or weed killers been used near the area of the plants? Accidental pesticide spray can harm plants. Also, have you planted other plants in this area in the past? If so, how well did they grow? Have you ever had the soil tested in this spot?

The problem may be too much water, which can cause root rot or fungal and bacterial diseases. Does the soil drain well? Most plants need about 1 inch of water a week - a little more in dry conditions. Your plants show signs of severe fungal leaf spot. My suggestions are:

-  If 2/3 of a leaf is affected, remove the entire leaf with sharp shears. If less, remove only the brown spots. Don't forget to disinfect the shears before using them. Try not to remove all the leaves from the plant, keeping the less infected leaves if needed.
-  Remove dry or blackened branches and flowers.
-  Clean all leaf debris from the area and dispose of it in the trash.
-  In severe cases, you may have to consider using a chemical fungicide. Check out a good garden center and look for a product that contains copper ingredients. Follow the label instructions carefully and make sure the product you choose lists delphinium.

Here are resources about growing delphiniums that you may find helpful:  https://libanswers.nybg.org/faq/223161
https://garden.org/learn/howto/grow/delphiniums/
https://extension.usu.edu/planthealth/news/delphinium-larkspur-pests

I'm sorry I couldn't be more definitive in my answer. I've given you a lot to consider, so don't hesitate to contact us again if you have more questions or need further information.

Have a good week.

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