How to prune sulphur cosmos

Deadhead throughout summer; cut back midsummer if plants become straggly. Remove spent blooms at the stem base or back to the next side shoot. For leggy plants, cut the whole plant back by one-third to one-half in midsummer; new growth appears within a couple of weeks.

Deadhead frequently; one mid-season cutback if needed. Sulphur Cosmos is a heat-loving annual that blooms continuously if deadheaded. It can become straggly in hot weather — cut plants back by up to half midsummer to stimulate fresh, bushy growth. Allow some flowers to set seed at season's end if you want volunteers the following year.

Remove spent blooms at the stem base or back to the next side shoot. For leggy plants, cut the whole plant back by one-third to one-half in midsummer; new growth appears within a couple of weeks.