Frost and plants left out!!

Hi

I didn’t realise the following were not frost tolerant and I think the frosts killed them ( I’ve attached pictures of the dahlia ) . So, I left raspberry cosmos in the ground , because my chocolate cosmos has reappeared every year, but the former looks all black& collapsing after minus 4 in Yorkshire! I’ve also left out tangerine coloured dwarf Dahlias in pots- they look bad - image attached and a giant red gazania in the ground , which has all wilted with the frost . We’re these supposed to be protected ?

 

Ordinary cosmos is an annual - quite different to chocolate cosmos. If the raspberry one is one of those, it's definitely gone. Dahlia top growth will get blackened by frost. The tubers may be ok, but if they're in pots, I'd recommend you store them somewhere now (after cutting off the top growth).
There's a current thread on how to keep them safe over winter with many suggestions.

 

oh maybe there’s hope thenn! The raspberry cosmos is in the woody shrub like genius similar to the chocolate cosmos, but the chocolate cosmos never wilts or goes black with frost and stays green most of the winter. I guess the gazania is gone too ?‍♂️ I’ll have a read on some of the other threads . Thankyou

 

Oh I've never heard of raspberry cosmos - I grew (and killed) the chocolate one in cold Nottinghamshire. Gazania are also pretty tender - if you garden in London you might get away with it.

 

Oh it’s pretty! Hopefully she’ll come back next year and I can get a picture! I’m in Yorkshire- so a lot colder lol Yes, I think the gazania a are heat loving unfortunately. Lesson learnt
I’m never sure how to protect the ground plants. Is it straw around the plant 7 cm
Thick AND fleece ??

 

The idea of winter protection for plants in the ground is to keep the roots or tubers dry and frost free. It's not too important about the top growth. So a layer of dryish compost or peat or peat substitute is good as it doesn't harbour slugs and snails, covered with a layer of old leaves, bark chippings, straw...any coarse material. If heavy rainfall is a feature of your climate, a sheet of plastic or weed membrane pinned down over tuberous plants like dahlias, cosmos or canna helps although you have to check regularly in early spring for new growth. Fleece is more use for protecting top growth, really, as it absorbs water when horizontal. In an emergency, a bucket or spring-loaded type garden rubbish bag upturned over tender plants can make all the difference and is quick and easy to remove when the temps rise again

 

I don't leave dahlias in the ground as they just wouldn't cope with the wet cold. That's more of a problem than dry cold @Shaneoak, so it really depends on your soil and climate as to what you do with them. If you want to be sure, it's better to lift, clean and dry them off, and then store. Cold wet ground is harder to deal with than dry cold, so that's where you have to judge it and proceed from there. Covering plant crowns with dry material will only work if the weather can't get through it, but the surrounding soil will absorb it, so that can affect dahlia tubers.
Mulching ,or adding some protection, around plants is also best done before weather/temps become too severe, as frozen ground will just stay like that. Insulation can keep cold in just as it does with warmth.

I don't tend to grow plants that need protection if planted out, so if I grow anything half hardy, I regard it as an annual, or I'd have to bring it inside for overwintering. The gazanias etc that you have are generally regarded as tender or half hardy, so they wouldn't survive outside in many areas without help. As @CarolineL says - in a sheltered town garden in the south, or similar, those might survive.
I think some people are able to keep the choc. cosmos going, as it's different from the annual type, but it doesn't manage here where I am, so I can't advise on those. If you find they normally survive for you, and the raspberry one is of the same type, it might be ok, so again - it's a case of judging it.

 

Thanks for the replies and tips . Much appreciated