READER’S QUESTION

SEVERAL of my colchicums have a few flowers left. Some of the clumps are congested. Can I dig those up and split them? If so, when is the best time?

Dorothy James, via email. YoU can divide them, but now is not a good time. Colchicums are not fully dormant until their spring top-growth withers. They’ll be dormant from then until late August. It’s best to dig up the plants when old top-growth is still visible. Tease the clusters apart then plant bulbs about 10cm (4in) deep.