My personal take on this, is that if the ground isn't waterlogged or frozen, you would be okay to do it. Depending where you are in the UK and if the forecast is reasonable, l would plant them with as much of the existing rootball and soil as you can, and maybe slightly deeper in their new planting positions. I have moved wallflowers just before they have flowered and they have survived. Others may have different opinions though
I have grown wallflowers in small pots, 2 in each overwintered them in my cold greenhouse, as today brought them out watered them and they will be planted in our front garden soon, just to fill some spaces do you think I should nip the tops out they are about 8 inches tall
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Depending where you are in the UK and if the forecast is reasonable, l would plant them with as much of the existing rootball and soil as you can, and maybe slightly deeper in their new planting positions. I have moved wallflowers just before they have flowered and they have survived.
Others may have different opinions though