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perennials winter care?

Hi all, 

I'm not planning on lifting any of these plants, so wondered if someone could advise on when and how to prepare these for winter in terms of cutting back and covering them?  I know some are hardy and some not.      Thanks in advance.

Veronica - is this hardy?


Verbena bonariensis - how much to cut back and when?  cover?

Dahlia bishop of llandaff - as above

Aster x frikartii - as above

Aster novi belgii - as above

Geraniums - left to die back naturally?     Are they then cut to the ground in spring?

Delphiniums - same as above?

Thanks all.



  • Hostafan1Hostafan1 Posts: 34,854

    Where are you Pierre? Location makes a lot of difference, as does your soil type. 

    eg, if you're somewhere mild and you have light sandy soil , you can leave Dahlias in the ground, but cold and wet soil is a different matter.

    More information would be useful.

  • Hi, I've got the verbena bonariensis. i usually cut it down in the spring, same with most of my perennials, as I don't like my garden looking bare over winter and it's supposed to be helpful for wildlife in the garden. I just mulch around them October time.

  • Veronica, asters, geranium and delphiniums are all hardy and can be tidied as necessary. I generally put some grit round delphs as slugs can easily beat me to the new growth in spring. image

    Some fuchsias are hardy, others not. If you have the variety name you can look it up to find out. It is probably best to leave it till spring to cut these back, as the stems help protect the roots. If it is a non hardy one you will need to lift it and pot it up and keep it somewhere frost free for winter. It needs minimal water, just enough to keep it ticking over, then you cut it back and begin watering when growth starts in spring.

  • In east midlands.   Have heavy clay soil.

    How thick a mulch are we talking for the verbena and dahlias?   Bark chips ok?

    For the geranium and aster etc do I cut to the ground in late winter as I would for say my achilleas and sedums?

  • raisingirlraisingirl Posts: 7,079

    yes, bark chips are ok - 2 inches is usually the recommended depth for mulch to be effective at keeping weeds down and the soil protected from the worst of the weather. It's very unlikely your dahlias will come though the winter in a heavy clay soil. I've never managed it on mine - they just rot.

    I leave verbena all winter and well into spring, it's tough as old boots and the birds love it. This does mean I get a lot of seedlings - it self seeds abundantly.

    Geraniums die back and I leave the dead growth in situ all winter - the dead growth protects the 'crown' of the plant if we should get a really hard frost Probably unnecessary for most of them.

    Asters I usually trim back to just above ground level once the flowers have gone over to stop wind rock - the old flower heads are quite heavy (and not particularly attractive) and flop around when they get wet. That can open up a gap around the base of the stems, rain gets in and either rots the roots, or frost forms and the whole thing just goes to mush.

    Veronica and delphinium, trim the stalks down but leave lower leaves to die back.

    All the old dead material and late cutting back (verbena) I clear or dig in during the March (or whenever the rain/snow stops for long enough) mulch/weed/tidy up of the borders. 

    Gardening on the edge of Exmoor, in Devon

    “It's still magic even if you know how it's done.” 
  • Hostafan1Hostafan1 Posts: 34,854

    I concur wholeheartedly with Raisingirl.

  • Raisingirl - thank you very much for these pointers.   I will certainly apply your advice.

    I was under the impression that the Verbena in question though was only half hardy - you say it's as tough as old boots?    I shall leave this in place then until March under your advice... for the Dahlia, I feared this would be the case.   Looks like there's no choice then but to lift.   Please can you tell me how would I go about this, and when?    Do I wait until all the foliage has died back, and does it need to be lifted before the first frost?    What would I expect to see on digging up the plant, and what pot would it go into?   Where would it need to be stored? 

    It was only planted a month ago or so....oh well.    Better than losing it.

  • Hostafan1Hostafan1 Posts: 34,854

    I'd leave the dahlia unitl after the foliage has been frosted. 

    It'll turn black and look awful, but it stops the plant trying to grow. 

    Be careful when you dig it up not to dig into the tubers. They'll be bigger than you expect . 

    I store mine in the polytunnel in dry ( ish ) soil and leave until they start to grow next spring. 

    A garage / cellar or shed also work well so long as the tubers don't freeze.

    Some start to water them in Spring to bring them on, but I leave mine to start when they're ready.

  • raisingirlraisingirl Posts: 7,079

    Verbena bonariensis is listed by the RHS as 'hardy throughout the UK'. Verbena rigida is less hardy. If you're sure it's bonariensis (very tall - my OH says it looks like a crowd of stick men waving their arms in the air) then it'll be fine.

    When you dig the dahlia up - and you should get a few weeks more from it yet unless we get a very cold snap early this year - it'll look like a sort of loosely connected bunch of bananas. You need to cut off the frosted shoots and then hang it up side down for a day or two so the water that may be inside the cut stalks runs out and then as Hosta says, buried in dry soil somewhere frost free and where it won't get wet. In about March you can plant it into a fairly big pot (9 inch, probably) and begin to occasionally water it, still keeping it under cover, and it will hopefully begin to shoot. 

    Gardening on the edge of Exmoor, in Devon

    “It's still magic even if you know how it's done.” 
  • Thanks to everyone for their advice, really helpful for me as well.  My Verbena Bonariensis self seeds and regrows every year and I just leave it to its own devices, although I ususally cut it back to the ground where it is a nuisance, such as along the paths.   

    I also have heavy clay soil and after trying leaving Dahlias in, lifting them, storing them dry, storing them in dry compost and all the other options I have given up and treat them as annuals, buying them as small plug plants in spring.  For me, and it is probably my lack of skill and knowledge, it is the easiest option.

    I also have Asters, which I cut back to the ground once the frosts brown them off.

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