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How to Grow Asters: The Complete Aster Flower Guide

purple aster flowers in a garden
Photo Credit
Pixabay
Botanical Name
Aster spp., Symphyotrichum spp.
Plant Type
Flower
Sun Exposure
Full Sun
Part Sun
Soil pH
Varies
Bloom Time
Summer
Fall
Flower Color
Blue
Pink
Purple
Red
White
Hardiness Zone
3
4
5
6
7
8
Special Features
Attracts Butterflies

Planting, Growing, and Caring for Asters

Catherine Boeckmann
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Asters enliven the garden in late summer and early fall when many flower blooms fade—providing a late-season treat for bees, butterflies, and other pollinators! Plant these deer-resistant native perennials to keep the color going. Learn all about planting, growing, and caring for asters.

About Asters

Cold-hardy perennials with daisy-like flowers, aster flowers are the pollinator stars of the garden from late summer through fall. Growing 1 to 6 feet tall, depending on variety, these upright flowering plants bear cheerful, star-shaped flower heads ranging from purple to white to blue.

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Even though there are more than 600 aster species, the two most commonly encountered asters in home gardening are the New England aster (Symphyotrichum novae-angliae) and the New York aster (S. novi-belgii). Several years ago, the Aster genus was split into multiple genera. Aster now covers most European and Asian asters, while those native to North America belong to Symphyotrichum.

Some hybrid varieties are available in showy colors, yet “wild type” species native to your region are generally a wise choice for the ecologically minded gardener despite not being quite as flashy as the cultivated varieties in some cases. Learn more about recommended varieties further down this page.

Aster is versatile: Depending on the height, it’s suitable for borders, rock gardens, or wildflower gardens. As well as being a valuable pollinator plant for bees and butterflies, its tasty seed heads are sought by cardinals, chickadees, finches, nuthatches, and many other seed eaters.

According to the North Carolina Extension, “Any species or cultivars of this genus would be a lovely addition to any home garden. It may be planted in a container for use on a porch or patio. It will also add color to a cottage garden or border garden. Butterflies and bees will appreciate the flowers, particularly as summer is ending and the evenings are getting cooler.”

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Planting

Asters prefer areas with cool, moist summers and cool nights in sites with full to partial sun. In warmer climates, asters do not like the hot midday sun. Soil should be moist but well-draining and loamy. Wet clay soil will lead to root rot, and dry sandy soil will lead to plant wilt. Mix 2 to 3 inches of compost into the soil before planting. 

When to Plant Asters

  • The best time to put young aster plants in the ground is in mid- to late spring after the danger of frost has passed. (See local frost dates.)
  • Or, you can plant mature, potted asters when available at garden centers (typically in the late summer or early fall).
  • Asters can be grown from seed, but germination can be uneven. If desired, plant seeds in the fall or start them indoors in the winter. 

How to Plant Asters

  • When planting young aster plants outside in the spring, space them 1 to 3 feet apart, depending on the type and how large they’re expected to get.
  • Fully grown asters, such as those available in late summer or early fall, should be planted about 3 feet apart.
  • If planting seeds, sow 1 inch deep in pots or flats and refrigerate them for 4 to 6 weeks to simulate winter dormancy. This cold period will kick-start germination.
  • Water well, and spread mulch around the plants to keep the soil cool and prevent weeds.
purple Aster and monarch butterfly
Asters are highly attractive to pollinators, especially bees and butterflies.

Growing

  • Add a thin layer of compost (or a portion of balanced fertilizer) with a 2-inch layer of mulch around the plants every spring to encourage vigorous growth.
  • If less than 1 inch of rain falls weekly in summer, water regularly. But beware: Many asters are sensitive to too much or too little moisture. They will lose their lower foliage or not flower well. Watch for stress and try a different watering method if your plants lose flowers.
  • Stake the tall varieties to keep them from falling over.
  • Pinch or cut back asters by one-third once or twice in the early summer to promote bushier growth and more blooms. Don’t worry; they can take it! Do the Chelsea Chop!
  • In winter, cut back asters after the foliage has died, or leave them through the winter to add some off-season interest to your garden. Birds may munch on the seeds, too.
    • Note: Aster flowers that mature fully may reseed themselves. The resulting asters may not bloom true to their parent. (In other words, you may not get the same color flowers you planted initially!)
  • Divide every 2 to 3 years in the spring to maintain your plant’s vigor and flower quality.
Varieties

The most common asters available in North America are the New England aster (Symphyotrichum novae-angliae) and the New York aster (Symphyotrichum novi-belgii). Both of these plants are native to North America and are great flowers for pollinators. We recommend planting a native species of aster over a non-native species when possible, so talk with your local Cooperative Extension or garden center about which species are best suited to your area. Look for varieties with disease resistance.

North American Asters

  • New England asters (S. novae-angliae): Varieties have a range of flower colors, from magenta to deep purple. They typically grow larger than New York asters, though some varieties are smaller.
  • New York asters (S. novi-belgii): There are many, many varieties of New York asters available. Their flowers range from bright pink to bluish-purple and can be double, semi-double, or single.
  • Blue wood aster (S. cordifolium): Bushy with small, blue-to-white flowers.
  • Heath aster (S. ericoides): A low-growing ground cover (similar to creeping phlox) with small, white flowers.
  • Smooth aster (S. laeve): A tall, upright aster with small, lavender flowers.
  • Aromatic aster (S. oblongifolium): Multi-branched at the base, stiff upright stems, with lavender or pink flowers.

European/Eurasian Asters

  • Frikart’s aster (Aster x frikartii) ‘Mönch’: Hailing from Switzerland, this mid-sized aster has large, lilac-blue flowers.
  • Rhone aster (A. sedifolius) ‘Nanus’: This aster is known for its small, star-shaped, lilac-blue flowers and compact growth.

Harvesting

Cut asters for flower arrangements when blooms are just beginning to open. Vase life is 5 to 10 days.

Asters have side shoots, which will continue to develop. These can be cut for indoor arrangements once they are the size you like.

Learn more about keeping cut flowers fresh.

Gardening Products

Pests/Diseases

Diseases: aster yellows; Botrytis blight; leaf spot, fungal; powdery mildew; rust; rot, Rhizoctonia root and stem, white smut, Fusarium wilt, Verticillium wilt.
Pests: aphids, foliar nematodes, slugs and snails, Tarsonemid mites.

Wit and Wisdom

  • The name aster comes from the Ancient Greek word for “star”—a reference to the plant’s star-shaped flowers.
  • Asters are called Michaelmas daisies because they bloom around September 29, the ancient feast day of St. Michael, and a quarter day, marking the transition to autumn. Learn more about Quarter Days!
  • Asters, one of September’s birth flowers, were once burned to ward off serpents.

The asters twinkle in clusters bright, 
While the corn grows ripe and the apples mellow. 
- Celia Thaxter

Flowers
About The Author

Catherine Boeckmann

Catherine Boeckmann loves nature, stargazing, and gardening so it’s not surprising that she and The Old Farmer’s Almanac found each other. She leads digital content for the Almanac website, and is also a certified master gardener in the state of Indiana. Read More from Catherine Boeckmann
 

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Comments

Sharon Dunfee (not verified)

9 years 7 months ago

Planted a lovely aster about 3 weeks (late August). The buds opened up and all was well. Then one morning I noticed every flower was gone from the plant. I have rabbits in my yard and I presume they are the culprits. What can I do to keep the rabbits from eating my aster blooms. They've not eaten the foliage, just the flowers!

Sharon - I used to have the same problem with rabbits eating my Aster (and other foliage). I read somewhere - probably Pinterest - to grate/shred original scented "Irish Spring" soap (which I found at the dollar store) to keep them away. I tried it this year and - viola! My Aster bloomed beautifully and my lily buds didn't get eaten! It didn't seem to harm any of the plants in my garden. This will be my go-to method from now on.

Rabbits do like to eat asters. If you are lucky you may have a second bloom from your plants if you can keep the rabbits away. Check our rabbit page for suggestions.
http://www.almanac.com/content/rabbits
 
 

Sheila Marler (not verified)

9 years 8 months ago

i have had my Aster for two years. It is a beautiful bright green plant, but has never bloomed. Could I have planted it to deep? Thank you, I have never trimmed it.

Hi, Sheila, This is a tough one because these are pretty forgiving plants. They perform best—bloom best—in full sun but tolerate part shade. (Perhaps only a little "part shade.") The do not like to sit in water, so well draining soil is important, and good quality—loamy or composted—soil helps. And add a shovelful of compost at the base in spring.
That's all we can say. The plant may have needed time to become established. Check these steps and see how it goes next year. (Yea, it is a long way off but never give up!)

SandiDe (not verified)

9 years 9 months ago

My asters seem to bloom early and early ever year. They are blooming now in July and before did not bloom until August or September, so I had color for the fall. Once they flower will that be it after the flowers die or will they rebloom until frost?

You can deadhead the blooms to encourage the plant to bloom again. If you keep up with removing the spent flowers before they set seed (remove the flower and stalk back to the next branch, leaf, or bud), the plant should continue to bloom until the end of the growing season.

Cat Hanson (not verified)

9 years 9 months ago

* planted many mixed mounding Asters around my walkways last fall in colors of red, white, blue, pink. These are all supposed to be only 18 - 24 inches tall and mound spread alike by bloom time. The white are 29 - 37 inches tall already and the crimson red are 24- 27 inches tall. Barely mounding yet . Pink and blue are in the normal range. Can I prune back the white and crimson red Asters to get them to be within the same height as the others are? Or my border is gonna be just way out of control around my walkways?

Hi Cat,
Yes, you can prune the taller asters. You may loose a few blooms but the plants will get bushier and you will have more flowers later in the season.

KaylaL (not verified)

10 years ago

I purchase some asters that were on sale in October and planted them in front of my house. I put some garden fabric down followed up by mulch. Now it's April, and my aster are brown and dry.. Did I kill them? And can I save them?