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How to grow asters

How to grow asters

All you need to know about growing asters, or Michaelmas daisies, in this detailed Grow Guide.

A table displaying which months are best to sow, plant and harvest.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Sow
Sow

Do not Sow in January

Do not Sow in February

Do Sow in March

Do Sow in April

Do not Sow in May

Do not Sow in June

Do not Sow in July

Do not Sow in August

Do not Sow in September

Do not Sow in October

Do not Sow in November

Do not Sow in December

Plant
Plant

Do not Plant in January

Do not Plant in February

Do Plant in March

Do Plant in April

Do Plant in May

Do not Plant in June

Do not Plant in July

Do not Plant in August

Do not Plant in September

Do not Plant in October

Do not Plant in November

Do not Plant in December

Flowers
Flowers

Plant does not flower in January

Plant does not flower in February

Plant does not flower in March

Plant does not flower in April

Plant does not flower in May

Plant does not flower in June

Plant does flower in July

Plant does flower in August

Plant does flower in September

Plant does flower in October

Plant does not flower in November

Plant does not flower in December

Take cuttings
Take cuttings

Do not Take cuttings in January

Do not Take cuttings in February

Do not Take cuttings in March

Do Take cuttings in April

Do Take cuttings in May

Do Take cuttings in June

Do not Take cuttings in July

Do not Take cuttings in August

Do not Take cuttings in September

Do not Take cuttings in October

Do not Take cuttings in November

Do not Take cuttings in December

Asters are in the daisy family and flower mostly in late summer and autumn, which gives them their common name Michaelmas daisy. Asters are ideal for growing in mixed borders, with grasses and other prairie-type perennials.

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Asters are a great transition plant, bridging the seasons from summer to autumn. The bright, daisy-like aster flowers make a colourful splash and provide a rich source of nectar and pollen for late-flying insects, and many varieties make good cut flowers.

In botanical terms there are two main types of Aster – north American and European. Most North American species come under the name of Symphyotrichum or Eurybia, but many people still refer to them as asters.

How to grow aster flowers

Grow asters in moist but well-drained soil in dappled shade or partial shade. Deadhead regularly to keep flowers coming, and cut back to the ground in late autumn. When shoots emerge the following spring, pinch out the tips to encourage more flowers to form.


Where to grow asters

How to grow asters - where to plant them
Planting asters with heather in a pot

Grow asters in dappled or partial shade, in any type of soil, although slightly moist soil (that never dries out) is preferable for species prone to developing powdery mildew. Asters can also be grown successfully in containers, again, preferably where the soil remains slightly moist or choose European asters, which have greater resistance to powdery mildew.


How to plant asters

Asters are easy to plant. Plant them as you would any perennial, ensuring they have plenty of space to grow and keeping them well watered as they establish. Watch our video guide with Monty Don on how to plant asters:


How to propagate asters

How to grow asters - aster cuttings in a pot
Aster cuttings in a pot

Increase your stock of asters by taking softwood cuttings between April and August (bear in mind that the process from taking cuttings to having flowering plants can take over two years).

Remove non-flowering shoots, cutting them down to a few centimetres in length, and then remove the lower leaves. Push each cutting into a pot of moist but gritty compost. Cover with a clear polythene bag or pop the pot in a propagator. Check the compost regularly and ensure it doesn’t dry out, so the cuttings have the best chance of taking root. Pot the cuttings into individual containers at the first signs of growth (after about six to eight weeks). Plant the young plants out in spring, and they will flower the following year.

Asters can also be propagated by division. Usually after around three years, the clumps are large enough to divide. Simply dig up and halve or quarter the clump with a sharp spade. Replant the clumps immediately into their new positions, and water well.


Growing asters: problem solving

Mildew is a common problem among many aster varieties, particularly the North American varieties. Keep plants well-watered and don’t let the soil dry out, but also look for varieties that are more mildew-resistant. European asters, including Aster amellus, Aster pyrenaeus and Aster x frikartii, are all mildew resistant, as are Eurybia x herveyi, and Symphyotrichum ‘Little Carlow’.


How to care for asters

How to grow asters - cutting back dead aster foliage
Cutting back dead aster foliage

Deadhead aster flowers to keep them looking good and to encourage more blooms to form. Cut aster plants back hard after flowering in late autumn. In midsummer, pinch out the top shoots to encourage flowers.


Advice on buying asters

  • Choose your aster flowers carefully – if you have drier soils then opt for European or certified mildew-resistant varieties
  • Always check plants for signs of damage or disease before buying or planting
  • Asters are available to buy from garden centres and nurseries but you’ll find a wider selection from specialist nurseries and online

Where to buy asters

Great aster varieties to grow

Symphyotrichum laeve 'Calliope'
Symphyotrichum laeve ‘Calliope’

Symphyotrichum ‘Ochtendgloren’ (pilosum var pringlei hybrid) – previously known as Aster ‘Ochtendgloren’, this has typical lavender flowers with bright yellow centres. A taller variety, it works well at the back of a border

Symphyotrichum laeve ‘Calliope’ – a particularly tall aster, with masses of small, lilac-blue flowers with yellow centres

Symphyotrichum novi-belgii ‘Samoa’ (‘Dasthree’) (‘Island Series’) – with purple flowers with bright yellow centres

Symphyotrichum ‘Coombe Fishacre’ – the small, lilac-blue flowers have yellow to purple-brown centres

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