I always start dahlias in the greenhouse, if they are in the ground the slugs eat them as they poke through. I feel safe with slug pellets on the bench in a greenhouse as the hedgehogs can't get in.
I start dahlias in my growhouse too, but with additional protection - usually just another clear plastic container, but with enough ventilation, which is very important to prevent rotting. Otherwise, it may need to be in the house, but it depends on the temperatures, as always. I grow mine mainly in containers, because of the problem with slugs. The ground isn't ideal for them here until later on.
It's a place where beautiful isn't enough of a word....
I live in west central Scotland - not where that photo is...
I think it should do OK in a pot so long as the pot is big enough and it is fed and kept moist. Use John Innes no 3 or soil and rotted manure mixed in with the compost.
Dordogne and Norfolk. Clay in Dordogne, sandy in Norfolk.
My Olivia Rose Austin does well in a large pot (45 cm diameter). I use 50% John Innes 3 mixed with 50% multipurpose compost, plus a couple of large handfuls of manure compost and another couple of large handfuls of horticultural grit. The pot is raised on pot feet to aid drainage. I prune it in late January and apply rose fertiliser in March, with liquid seaweed diluted in the water I use to water it every other week from May to September. Watered weekly with ~12L of water in summer, maybe more often if very hot. It has a lovely scent, but not very strong to me.
@zakzak I visited David Austin last year the rose garden was at it's best .R Olivia Austin stood out amoungst some very beautiful roses. The fact that it is named after a family member seems to be a good indication as to just how good.
I have worked as a Gardener for 24 years. My latest garden is a new build garden on heavy clay.
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I live in west central Scotland - not where that photo is...
https://www.davidaustinroses.co.uk/products/olivia-rose-austin
I think it should do OK in a pot so long as the pot is big enough and it is fed and kept moist. Use John Innes no 3 or soil and rotted manure mixed in with the compost.