On the assumption you mean Spiraea, as with most shrubs, September/October is best, but otherwise, March, so long as the ground is not frozen or waterlogged.

I also think the same but a pot bought plant can be planted anytime but as bamboo said these are the best times. If you have to get it planted now then as long as the ground isn't frozen it will be fine. planting in the summer means you will have to make sure you water it well.

Seaburn, does your advice apply to “anything “? I have seedlings of Hellebores and Sweet woodruff in the greenhouse, and thought the soil might be too cold to plant them out just yet. My instinct is to keep them in a cold frame until March, but what would you do?

As long as the ground isn't frozen or waterlogged then they can be planted out after a week or two getting used to being out of the greenhouse. I'd harden them off first then plant out. I noticed lots of hellebore seedlings in the garden today. Obviously if snow/frost forecast then protect them. once in the ground they are less likely to die of the frost..

Many thanks Eileen.

Thank you