How to Trim a Carolina Aster

Wipe the blades of your shears with rubbing alcohol. Carolina aster is prone to fungal infections, which easily enter pruning wounds via dirty blades.

Trim the Carolina aster back to one-third of its size in early spring, just as it begins to put on its new growth for the season. Simply eyeball a point two-thirds of the way down from the top of the plant, and cut straight across with lobbing shears. Don't worry if the thin, hacked stems look unsightly. They will quickly grow out.

Gather the aster's cut foliage and compost it, or throw it away. Do not leave twigs dangling inside the plant or lying on the ground. The dying foliage may develop fungal colonies that could attack the living plant tissue nearby.

Examine the Carolina aster's remaining foliage for fungal growth or dead or wilted branches. Use pruning shears to cut these branches back to the nearest fork -- or back to their point of origin if necessary. After periods of prolonged rain or humid weather, re-examine your aster's foliage. These conditions could spur fungal growth, so vigilance and quick pruning are key.

Prune your Carolina aster again in May or June if necessary.