Montane Knapweed

How to grow Montane Knapweed

Written by the GardenDecoded editorial team · Last reviewed 21 July 2026 · Written for UK gardens · How we research our guidance

Planting

Plant in autumn or spring in any reasonable soil. It is not fussy and flowers early, filling the gap between spring bulbs and the main summer border. It spreads by short runners and forms a broad clump.

Pruning

Cut the whole plant back hard to the base immediately after the first flush finishes, usually late June. Fresh foliage and a second flush of flowers normally follow. Left uncut it becomes sprawling and mildewed by midsummer.

Propagation

Divide in spring or autumn; it splits easily and division every few years is worthwhile. Self-sown seedlings appear and are simple to move.

Pests and diseases

Powdery mildew is very common on the old foliage from midsummer, which is the main argument for cutting back hard. Otherwise trouble-free.

Value to wildlife

Bees and hoverflies work the flowers, and there are nectaries on the outside of the flower buds that attract ants and other insects before the flower even opens.

Notes

The unattractive middle age of this plant is entirely avoidable. Treat the July cut-back as compulsory rather than optional and it stays presentable all season.

This guidance was researched and written by GardenDecoded — see our editorial policy for how guides are checked and reviewed.

Other names for this plant

These names have all been used for Centaurea montana but are no longer the accepted name. You may still meet them on old labels, in books, or in nursery catalogues.

Others in Centaurea