Black spots on Polypodiums

This topic contains 5 replies, has 2 voices, and was last updated by  Jack 4 months, 1 week ago.

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  • #16254

    Jack
    Participant

    Hiya,
    I have quite a few different Polypodiums and a few develop black spots on their fronds fairly regularly. I read somewhere that this might be due to the medium being too wet for them.
    Is that correct?
    Thanks,
    Jack

    #16255

    Andrew Leonard
    Keymaster

    Are you growing them outside or indoors?
    What time of year does this happen?
    Can you provide a picture?
    images should be no larger than 600 x 900 pixels

    #16275

    Jack
    Participant

    Hi Andrew,

    They are all grown outside, for some it is happening now with small black spots, for Polypodium scouleri it happened in early summer with larger black areas just after the first flush of leaves and after very heavy days of rainfall so the pot was very wet. The scouleri is still growing vigorously.

    I’ve attached some pictures of the one the has just now developed black spots in the last week Polypodium x mantoniae ‘Cornubiense’. I really like this one so wanted to catch it early if I am doing something wrong.

    Thanks,

    Jack

    #16283

    Andrew Leonard
    Keymaster

    This is what the BPS Horticultural Information Adviser has to say:

    I have had a careful look at the pics. I cannot come to a firm conclusion about the spots. None of mine are showing such symptoms. How long has the ‘infection’ been noticed?

    We need a much closer look at the effect of the damage on the sori on the reverse side of the frond. I am inclined to think that it is some sort of fungal infection, perhaps Martin has had experience of this infection.

    It needs looking at microscopically……….Matt Busby

    #16301

    Andrew Leonard
    Keymaster

    and this is what Tim Pyner thinks:
    I agree with Matt and think the spots are a fungal infection. They seem to be associated with the sori on the under surface. My P. scouleri often have blackish areas on the fronds. I suspect both are caused by water logging combined with poor air circulation.

    and this is what Martin Rickard has to say:
    I broadly agree with the others. I have the problem and just put up with it! If it is fungus you would need to find out what type so you could think about type of fungicide. Or you could try several different chemicals. On the other hand I have heard comments, mainly from Continental growers, that this is caused by nematodes. I have no evidence to support or deny this. If it is, you cannot really do anything about it! Are these grown under trees? Could it be water drops? Personally I would not worry too much about it. It might not recur next year if the weather is different.

    Sorry not to be able to offer more constructive advice. Enjoy your polypods – they are wonderful!

    #16335

    Jack
    Participant

    Hi Andrew and everyone who responded.

    That is very constructive and helpful, thank you very much.

    I’ll not worry about it for now and see what happens when the weather warms up and the new growing season is upon us. The situation hasn’t become any worse so far.

    They’re on a patio in a slightly shady spot but not under trees.

    The growing medium has been very wet in the recent rains, not helped by being sited on a concrete patio.

    I’ll report back if there is any significant change (positive or negative)

    Thanks,

    Jack

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