Aster
Aster novi-belgii
A bushy, clump-forming perennial producing masses of daisy-like flowers in shades of blue, purple, pink, and white from September to November. Michaelmas daisies are among the finest autumn-flowering perennials for UK gardens, extending the season well beyond the first frosts. They provide critical late nectar for bees and butterflies preparing for winter.
How to grow aster
Plant in spring in fertile, moisture-retentive soil in a sunny or lightly shaded position. Space plants 45-60 cm apart. Water regularly during dry spells, as asters in dry soil are far more susceptible to powdery mildew. Mulch with garden compost each spring and feed with a balanced fertiliser in April. Use the Chelsea Chop in late May — cut all stems back by a third to produce bushier, self-supporting plants that flower slightly later. Divide clumps every two to three years in spring, replanting only the vigorous outer sections and discarding the woody centre. Choose mildew-resistant cultivars where possible.
Pruning
Deadhead faded flowers to keep the display tidy but many gardeners leave the last flush for wildlife. Cut all stems back to ground level in late November once flowering has finished. Thin emerging shoots in spring to six or seven per clump for larger individual flowers.
Propagation
- Division in spring
- Basal cuttings in spring
- Softwood cuttings in early summer
Common problems
- Powdery mildew on foliage
- Wilt disease causing sudden collapse
- Slugs on young spring growth
Good companions
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