5 pointers for growing aster in autumn

Just when you think there's nothing to look forward to in the garden except falling leaves, asters arrive in autumn with cool blue and silvery pink flowers. Follow these 5 pointers to fully enjoy this easy-to-grow plant.

5 pointers for growing aster in autumn

1. Plant asters in the right spot

  • Asters often bloom in tandem with chrysanthemums, but this partnership works best with compact aster varieties that match the mums in terms of plant form and stature
  • Plant taller asters, which usually require staking, near fences so they can be tied to posts or open rails
  • Combine with good neighbouring plants such as goldenrod, sneezeweed and the last of the marigolds and rudbeckias

2. Choose the right aster for your garden

  • Most of the asters sold by nurseries are descendants of two North American native species: New England aster (Symphyotrichum novae-angliae) and New York aster (S. novi-belgii), including hundreds of named cultivars
  • If ease of culture is your goal, begin with a naturally compact cultivar, such as 'Purple Dome', which grows to only 45 centimetres (18 inches) tall and needs no pinching or staking
  • Where you want more height, consider 'Hella Lacy', a one metre (three foot) purple bloomer with excellent cold hardiness and good resistance to fungal leaf disease

3. Avoid leaf disease

  • Disease can be a worry with many asters when they grow in warm, humid climates
  • If you notice fuzzy or moldy-looking spots on the foliage, trim off affected leaves and prune back or space plants widely to increase air circulation
  • Consider growing a disease-resistant aster, such as the shade-tolerant white wood aster (Eurybia divaricata), which has starry white flowers and is happy under larger shrubs or in the dry shade of trees
  • Plant Aster × frikartii,  another disease fighter, which flowers prolifically with big blooms and is very vigorous

4. Provide low-maintenance care

  • Set out purchased plants in spring in soil that is of average fertility
  • Add a scant ration of fertilizer to help get new plants going, but avoid feeding asters after summer begins
  • Fo not over fertilize, these tough flowers prefer to fend for themselves. Too much fertilizer can make them grow big but weak-stemmed and short on flowers
  • Pinch back tall varieties at least once, in early summer, to encourage branching
  • Stake or tie up the stems when they have grown more than 0.6 metres (two feet) tall

5. Increase the bounty

  • After only two to three seasons, asters grow into large, crowded clumps. To relieve crowding, either pinch out one-third of the new stems soon after they appear in early spring, or dig up and divide the clump if you want to expand your collection
  • Dig small divisions from the outer edges of a clump well into early summer
  • If transplanted promptly and given plenty of water, the new divisions will bloom heavily in fall the same season

These low-maintenance plants can take the spotlight in your garden after the flowers of spring and summer have passed. Asters' starry blue or pink blossoms with yellow centres are so numerous that they often hide their leaves entirely. Follow these pointers to get them growing for you.

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