Quick Guide: summer, half-hardy, full sun, height: 12-30cm/5-12in, width: 15-30cm/6-12in
Ageratum houstonianum is a native of Mexico and is sometimes listed as A. mexicanum. It produces mounds of small, soft-looking, daisy-like flowers amid heart-shaped leaves. It is an excellent choice for edging or for the front of the border, since the blue, white or pink flowers bloom from early summer through to autumn.
PROPAGATION Sow seeds in gentle heat in early spring and prick the seedlings off into boxes at 5cm/2in apart when they are large enough to handle. Harden off before planting out in early summer.
GROWING A well-drained fertile soil is best. Water the plants well in dry weather and dead-head regularly to ensure a succession of blooms.
VARIETIES Choose F1 hybrids such as `Blue Surf', `Fairy Pink' or `Summer Snow'.
POSSIBLE PROBLEMS Foot rot and root rot may occur, causing plants to collapse.
