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3rd year now,potted Cosmos bottom leaves turning brown and somne plants have silner lines on leaves. This year, new pots new compost same problem. Could someone tell me if spores from the potted plants transfer to the ground the pots stand on. I have read that these plants cannot be grown in the ground for five years, but I cannot understand why pots are affected. Thank ou for any advice.


  • FairygirlFairygirl Posts: 54,811
    edited September 2021
    Have you a photo?
    Cosmos will naturally look rough lower down as the plants age, especially when they're in pots.. Many perennials and annuals are the same by this time of year. 
    They aren't really affected by any pests and diseases which would last year on year either. They're fairly trouble free for most people.  :)
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • Trouble could be blowing in on the wind from another source?
  • Pete.8Pete.8 Posts: 11,287
    I've grown cosmos for many years without any trouble until this year.
    The plants start out growing vigorously but then the leaves went pale and got covered in spots, the flowers died off and then the plants too.
    I happened to about 15 plants out of 20.
    Very disappointing and I don't' know why other than it seems to be a fungal infection of some sort

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • Hi, I took a leaf to my local garden centre and was advised that it isFusarium Wilt. There is no treatment for this problem which is a soil borne fungus. Apparently you will be unable to grow Cosmos in the immediate area for five years!! I am devastated as I love my garden full of these beautiful flowers.
  • Pete.8Pete.8 Posts: 11,287
    It may be fusarium wilt, but there are other possibilities such as phytoplasmas which cause similar-looking problems. This is a bacterial infection transmitted by insects.

    Of my plants some were affected but others within a couple of feet were ok.
    I have patches of cosmos here and there all over my garden and each patch of cosmos had a few affected plants, so I rather doubt that most of my 150ft garden has suddenly become infected with fusarium wilt.
    I'll be planting cosmos in the same areas next year, so will keep my fingers crossed and see what happens.

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
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