How to prune ageratum houstonianum 'blue horizon'

Deadhead throughout summer; optional midsummer shear when first flush fades. Remove spent flower clusters by cutting back to the nearest leaf node or lateral bud. For a fuller refresh, shear the top one-quarter of all stems with clean shears in midsummer, then water and fertilize lightly.

Deadhead every 1–2 weeks; optional single mid-season shear. Ageratum 'Blue Horizon' is a tall, cut-flower-type ageratum that benefits from deadheading as clusters fade, extending the blue display. Without deadheading, plants set seed and slow down. A light shear by one-quarter when flowering wanes in midsummer encourages a fresh late-season flush. It stays upright and rarely needs structural pruning.

Remove spent flower clusters by cutting back to the nearest leaf node or lateral bud. For a fuller refresh, shear the top one-quarter of all stems with clean shears in midsummer, then water and fertilize lightly.