My mimosa tree is getting a bit overcrowded, and I would like to prune it. When should it be done?

Cut back branches fairly severely in the spring after flowering.

New growth will develop in the summer, and should flower the following spring.

The leaves of my Mimosa pudica shrivel and die, what is causing this?

Mimosa pudica (sensitive plant) is a short lived sub shrub, and is usually treated as an annual by sowing seed each spring.

You could try to keep your plants over the winter in a warm greenhouse.

The possible cause of the shrivelling leaves may be because the plant has been kept too dry at some stage.