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Over wintering plants

I recently bought two Dahlia plants, Bishop of Llandaff and Mystic spirit also a Cosmos 'chocamocha' plant as i want to redo a border in my garden. It then dawned on me that i should maybe have waited untill spring to purchase them as im sure they cannot stay in the ground over winter, they are still in the pots i purchased them in. I was hoping someone could give advice as to the best way of overwintering them i do have an unheated greenhouse, but never seem to have much luck with overwintering plants. Also is it possible to take cuttings/safe seeds from all three. Many thanks.


  • SingySingy Posts: 206

    I have a couple of Dahlias i will be overwintering in the spare room, i dont think this is the correct way to do Dahlias, i think you are supposed to lift and store.

    Here is the link to the RHS guide on Dahlias

    Cosmos will be similar i suppose

  • punkdocpunkdoc Posts: 14,605

    The best thing to do with dahlias is to wait until frost has blackened the tops, chop the foliage down to a couple of inches, dig up the tuber removing most of the soil, allow to dry out by turning them upside dowh [ allows moisture to drain from the stems ], then store the tubers somewhere frost free. I wrap loosely in paper and store in a box in the porch. The longer the tubers are in the ground the more the tubers will develop.

    How can you lie there and think of England
    When you don't even know who's in the team

    S.Yorkshire/Derbyshire border
  • Kim63Kim63 Posts: 15
    Thank for the replies... Think I'll leave them in their pots and keep in the greenhouse away from frosts until spring.
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