Aster

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Botanical name: Aster

Plant type: Flower

USDA Hardiness Zones: 3, 4, 5, 6, 7, 8

Sun exposure: Full Sun, Part Sun

Soil type: Loamy

Soil pH: Varies

Flower color: Red, Pink, Purple, White

Bloom time: Summer, Fall

Asters are daisy-like perennials with starry-shaped flower heads. They bring delightful color to the garden in late summer and autumn when many of your other summer blooms may be fading.

The plant's height ranges from 8 inches to 8 feet, depending on the type. You can find an aster for almost any garden and they have many uses, such as in borders, rock gardens, or wildflower gardens. Asters also attract butterflies to your garden!

Planting

  • Asters prefer climates with cool, moist summers, especially cool night temperatures.
  • Select a site with full sun to partial sun.
  • Soil should be moist, well-drained, and average to humus-rich.
  • While the plant can be grown from seed, germination can be uneven. You can start the seeds indoors during the winter by sowing seeds in pots or flats and keeping them in the refrigerator for 4 to 6 weeks. After 4 to 6 weeks, put the seeds in a sunny spot.
  • Many gardeners purchase a potted plant from the nursery and plant in the spring.
  • Space asters 1 to 3 feet apart, depending on the type. 
  • Remember to stake the taller varieties.
  • If you're replanting shoots, use vigorous, young shoots to ensure best growth.

Care

  • Add a thin layer of compost with a 2–inch layer of mulch around the plants every spring.
  • If you receive less than 1 inch of rain a week, remember to water your plants regularly during the summer. However, many asters are moisture-sensitive; if your plants have too much moisture or too little moisture, they will often lose their lower foliage or not flower well. Keep an eye out for any stressed plants and try a different watering method if your plants are losing flowers.
  • Stake the tall variesties in order to keep them upright and remember to pinch the young shoots to encourage bushiness.
  • Divide every 2 to 3 years in the spring to maintain your plant's vigor and flower quality.

Pests

  • Susceptible to powdery mildew, rusts, white smut, leaf spots, stem cankers, aphids, tarsonemid mites, slugs, snails, and nematodes. Choose disease-resistant varieties.

Recommended Varieties

  • King George (Aster amellus), for its large, violet–blue flowers
  • Silver spray (Aster cordifolius), for its pink-tinged white flowers
  • Nanus (Aster thomsonii), for its star-shaped, lilac–blue flowers

Special Features

  • Attracts Butterflies

Wit & Wisdom

Asters, September's flowers, were once burned to ward off serpents.

Free E-Card

Send this lovely e-card of a butterfly on asters to your friends and family.

Comments

By Anonymous on May 17

I know I have to cut my mums back by half in mid-summer. Should I prune back my aster too? Its our first year.

By Almanac Staff on May 22

Instead of pruning the asters try pinching the tops of the stems for a fuller aster with more flower buds.

By Anonymous on May 7

I just bought some blooming aster starters. How should I plant them? 2 or 3 to a cluster? Or separately? All that is on the pots is height 8", width 6", and sun.

By Almanac Staff on May 22

Depending on the variety, plant them 1 to 3 feet apart.

By Anonymous on May 2

Will these grow towards sun (lean) in partial sun or grow straight up?

By Almanac Staff on May 22

The taller aster varieties need to be staked so that they don't lean or fall over.

By Anonymous on April 27

I have started asters from seeds and am now transplanting into a larger pot. How many shoots should I have in each pot? Now there are 4-5 in each one.

By Anonymous on April 29

There should be 8-14 shoots in the pot.

By Anonymous

i've left unplanted asters in original nursery plastic pots on my patio during the winter....can i salvage these??

By Anonymous

Anyone know the time to germination? And time to bloom?

By Almanac Staff

Germination for aster seeds is generally 7 to 14 days, depending on the type. Days to maturity should be on the packet--some types are 75 to 80 days. They often have a nice long bloom duration, perhaps 4 to 6 weeks if you deadhead and take care of them.

By Anonymous

Is it ok now in January to shear 1/3 of the top of my Asters?

By Almanac Staff

Sure. You can prune your asters now. They will send up new growth come spring.

By Anonymous

i have asters in pots outside and in the ground they have died off now (brown and brittle leaves) if i cut them rite down will they come up again

By Almanac Staff

No need to cut them down. A layer of mulch will keep moisture in the soil and protect against extreme temperatures. Store the potted asters in a garage or shed. You can also dig a hole in your garden and set the pot in the hole for extra protection. Next spring you can lift the pot and put it back on your porch.

By Anonymous

Can the cut flowers be left for germination or saved for Spring?

By Almanac Staff

Asters can be propagated by division or by planting seed in the spring. If your cut flowers had gone to seed you can save the seeds. Best time to divide an aster plant is in the spring. Cut a mature plant into 3 to 4 sections and plant each section in the garden. Asters grow quickly and will fill out in no time.

By Anonymous

I was told to cut my aster down to the ground which I did. Do I have a problem. Also - how do tell the difference between and 8" and 8' plant? A novice!!

By Almanac Staff

No worries. The asters will grow back.
There are many varieties of asters and some can grow to 8 feet tall when mature. If you know what variety you planted you can look it up online and see how tall it may grow.

By Anonymous

I live in Indiana, do I cut down my plants to the ground and mulch them for winter? The flowers are all gone....

By Almanac Staff

No need to cut them down. A layer of mulch will keep moisture in the soil and protect against extreme temperatures.

By Anonymous

I purchased asters in early October and put them in large pots with pansies. Since they are perrenials, will they come back next spring if I leave them in pots all winter on my porch. I live in central Oklahoma.

By Almanac Staff

It depends on how cold it gets. To be safe store the pots in a garage or shed. You can also dig a hole in your garden and set the pot in the hole for extra protection. Next spring you can lift the pot and put it back on your porch.

By Anonymous

I just bought an aster (not sure what type) it is october in illinois,can i put it in the ground now,or should i pot it and wait till spring? The lady i bought it from said they are hardier than mums,i planted those in late spring after potting and leaving outside all winter? however,we had a mild winter. so im just not sure. also, we have cats,so im reluctant to bring it inside. any advice?

By Almanac Staff

As long as you have a perennial aster, you can plant it now. Water and add mulch after planting. If you decide to bring it indoors, try putting citrus peels in the pot to keep the cats away.
Good luck!

By Anonymous

I received a small aster plant in early Sept. as a gift. Is it OK to plant that aster now-- mid-October to early Nov??

By Anonymous

Should I deadhead the dead flowers to encourage new flowers as I do my roses?

By Almanac Staff

Yes. You can pinch off the fading flowers during the growing season to encourage more blooms. Some gardeners also shear off the top 1/3 of taller asters (not dwarf types) in early summer to encourage fuller growth with more blossoms, although this can delay blooming.

By Anonymous

my aster seems to attract flies...lots of flies would insecticidal soap stop them from comimg to the plant??

By Sarah Perreault

Give mint a try. Flies do not like the smell. Either set out some pots of mint near your asters or crumble mint leaves all around the plants.
Good luck!

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