Astilbe Amethyst Roots

Question

I was wondering at what time of year I should plant them.

Answer 1

I should also add that you can start them earlier by placing in pots with a good commercial potting mix.
They can be placed in a cool greenhouse or a cold frame. You will need to keep them in bright light but above freezing temperatures.
You can then plant them out when weather warms.

Answer 2

Plant out any time after danger of frost has passed in the spring.

https://www.gardeningknowhow.com/ornamental/flowers/astilbe/bare-root-planting-astilbe.htm