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Can compost be too strong?

I have stunted yellowing brassica seedlings. They are in 2" square modules of West Riding potting compost. I used to use their seed and module compost but it didn't have enough go in it to take brassica seedlings to the bulky 4 leaf stage. Can compost be too strong? I am reluctant to go out and buy different compost because I have - I know - 96 eighty litre bags of this stuff. Lettuce and salad crops, sweet corn and all the toms and squashes are doing fine - brassicas - awful.

Comments (2)

  1. Grower


    All brassica need untreated and compost free soil to grow.

  2. Grower

    Geoff Hodge

    It all depends on the compost and its fertiliser make up. Some multi-purpose compossts are just that - and have quite a lot of nutrients, so they can be used as a potting compost. Some are OK when used with large seeds, but I tend to only use them for potting up and potting on.
    I always use a seed and cuttings compost for sowing small seeds.
    Never use old compost left over from year to year - or buy compost in old, faded bags. The nutrients in here can easily build up to 'toxic' levels, which will damage seeds and seedlings.
    I don't know and have never tried the composts you refer to, so can't comment on them.

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