new to gardening, how late can i plant out hardy perennials

we recently moved to a house with a huge front and back garden, so i thought i would get my self a greenhouse and do the garden up nice.. instead of buying plants i bought A LOT of hardy perennial flower seeds different species (supposedly able to stand -15C) is it too late to plant these out after germination or will they still be able to withstand the frosts here in the UK, its only a small 6x4ft greenhouse so i don't think there is enough room to keep them in there over winter

thanks

ps the seeds have not been sown yet, just waiting for some info on what to do

 

Hi Jack, welcome to GC..

You can sow perennial seed pretty much anytime between Feb & Sep, although the spring is better as you'll have better sized plants by the winter.

I would go ahead and sow them Jack, this spring has been so on the whole that I doubt they'll end much behind a lot of earlier sowings which many are saying are slow to get going.

It all depends on what species you are growing as to whether you'll have a garden ready plant within the first year; the more vigorous ones should be fine to plant out in the autumn (which is an excellent time to plant out as the ground will still be warm and they should establish wel before the cold weather comes). I always like to grow mine on in pots for a year before planting out; they wouldn't necessarily need to be kept in a greenhouse over winter, a sheltered corner would be fine and if any severe weather is forecast just throw some fleece over them, they're hardy after all, they'll just need a little tlc through their first winter.

Good Luck and have fun

 

Hi there Jack,
what service eh? GC is the place to join for rapid, pukka replies!! Welcome,
Jenny namaste