How to Prune a New England Aster to Delay Blooming

Spray down the blades of your pruning shears and bypass pruners with household antiseptic cleaner before use to eliminate any traces of fungus or disease from previous prunings. Wipe the blades dry with a paper towel.

Shear your New England asters back by half their height in mid-June, or whenever the plant reaches 12 to 16 inches tall, to encourage fuller growth. New England asters can sometimes grow as tall as 6 feet, but tend to become leggy and top-heavy when they get past 3 feet tall.

Clip back any long stubs to just above a leaf to avoid an untidy look. Trim stems higher in the center of the plant and shorter around its perimeter so your aster grows out into an attractive dome shape.

Shear the plant back by one-third to one-half again -- with clean pruning shears or bypass pruners -- in mid- to late July, or when the plant is 3 to 4 feet tall. This will shorten it and delay blooming by about two weeks.

Pinch developing flower buds off the tips of the plant as they develop in late summer through early fall, or simply shear off the top 4 inches of the plant, to delay flowering for two weeks without losing significant height.