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Late-Season Garden Blooms: How to Grow and Care for Asters

purple aster flowers in a garden
Image Credit:
Pixabay
Botanical Name
Aster spp., Symphyotrichum spp.
Grown as
Perennial
USDA Zones
3a
3b
4a
4b
5a
5b
6a
6b
7a
7b
8a
8b
Toxicity
Non-toxic
Sun Exposure
Full Sun
Partial Sun
Water Needs
Moderate
Height
1–3 feet
Spread
1–3 feet
Soil pH
Neutral
Bloom Time
Summer
Fall
Flower Color
Blue
Pink
Purple
Red
White
Special Features
Container-Friendly
Cut Flower
Fall Color
Long Blooming
Low Maintenance
Winter Interest
Attracts Butterflies
Attracts Pollinators
Attracts Songbirds
Resilience
Clay Soil Tolerant
Cold Hardy
Drought-Tolerant
Heat-Tolerant
Plant Type
Flowers
Written By: Catherine Boeckmann Executive Digital Editor and Master Gardener

When the garden’s summer show starts to fade, asters steal the spotlight. These daisy-like perennials don’t just brighten your borders—they’re buzzing with pollinator drama! 

Bees, butterflies, and even birds can’t resist these late-season stars, making asters the must-have finale for any garden.

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.

Buy Seeds Now

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 State Extension, any of the commonly available varieties of this genus “would be a lovely addition to any home garden.” Aster may be planted in a container for use on a porch or patio, the extension notes. 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.

Planting

Where to Plant Asters

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

Watering

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.

Fertilizing

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.

Pruning

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!

Seasonal Care

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.

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.

Pests and Problems

Diseases: aster yellows; Botrytis blight; leaf spot, fungal; fusarium wilt; powdery mildew; rhizoctonia root and stem; rot; rust; verticillium wilt; white smut.
Pests: aphids, foliar nematodes, slugs and snails, tarsonemid mites.

FAQs

When is the best time to plant asters?

Plant asters in spring after the last frost or in early fall. Spring planting allows roots to establish before the heat, while fall planting lets perennials overwinter and bloom next season. 

How tall do asters grow? 

Depending on the variety, asters can grow anywhere from 1 to 6 feet tall. Choose shorter varieties for borders or containers and taller ones for the backs of flower beds. 

Which asters attract the most pollinators?

Native asters like New England and New York asters are particularly popular with bees, butterflies, and seed-eating birds. Planting a mix of colors and heights boosts pollinator visits. 

How should I care for asters? 

Asters prefer full sun, well-draining soil, and moderate watering. Deadhead spent flowers to encourage continuous bloom and cut back plants in late fall to maintain healthy growth. 

Are asters deer-resistant?

Yes! Most asters are considered deer-resistant, making them a great choice for gardens where deer are a concern.

Types

Even though there are more than 600 aster species, the most common asters available in North America are the New England aster (Symphyotrichum novae-angliae) and the New York aster (S. 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

  • Aromatic aster (Symphyotrichum oblongifolium): Multi-branched at the base, stiff upright stems, with lavender or pink flowers.
  • 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.
  • 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 varieties of New York asters available. Their flowers range from bright pink to bluish-purple and can be double, semi-double, or single.
  • Smooth aster (S. laeve): A tall, upright aster with small, lavender 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.

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, American poet (1835–1894)

Flowers

About The Author

Catherine Boeckmann

Catherine Boeckmann

Executive Digital Editor and Master Gardener

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

<a title="View user profile." href="/author/editors">The Editors</a> Mon, 09/22/2014 - 11:45

Check the soil about 2 inches below the surface to see if it is moist. If not the plants need more water. Add mulch around the plants. Asters like cool temperatures and will do better when the night temperatures drop below 60.

 <span>Mbr</span> Mon, 09/15/2014 - 01:39
"Last year, purchased and planted several potted "daisy like" asters, bearing the "annual aster" tag. Some were blue, and some purple. Since I do not care for the pin cushion looks of mums, I was delighted to find those beautiful daisy looking flowers with the yellow centers., even though they were annuals. I am in Nebraska, and was a bit surprised when they came up in the spring, again, and bloomed this fall. My issue? They are full and compact, with a profusion of purple and blue flowers. However, they no longer present with a daisy like appearance. They resemble the full, rounded flower of a mum, with no yellow center. I retained the marker, left in the ground from last year, to confirm that they were indeed the same flower. I have no mums planted in this flower bed. Any idea what happened?
<span>Dennis Mcclure</span> Sun, 09/07/2014 - 17:48
how can i tell if the astors that i just bought are perennial or annual. I still have the label from the plant but it does not specify either annual or perennial?
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 09/09/2014 - 07:19

Most asters are perennials. The most popular are Michaelmas daisies which are about 12 inches tall. Annual asters are popular with florists for cut bouquets. The popular Chinese aster resembles a daisy but showier and more colorful.

 <span>Deveral Watson</span> Sun, 09/07/2014 - 15:55
I planted arrow-leaved aster, over 5' tall and as wide. Aug. just budding. Sept. producing just the yellow center with 9 green petals. I expected blue with yellow centers. Have you known this to happen before?
<span>Kathleen A. Ryan</span> Sun, 08/17/2014 - 13:42
Hello. I purchased astors last Fall from a nursery. I planted them and they survived the N. Idaho winter very well. They are now very hearty, compact bushes- very uniform in size and shape. It is the middle of August and I have yet to see any evidence of buds or flowers. Is it just too early for them to bloom, or have I done something wrong? Thank you.
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 08/19/2014 - 09:14

Hi, Kathleen: Assuming that your plants are getting good water and sun, chances are that they are a fall-blooming type and are just biding their time to surprise you in a few weeks. Thanks for "ast"-ing!

 <span>I<3Gardens</span> Wed, 07/30/2014 - 20:01
I live in Minnesota and my grandma from Texas sent me some aster seeds. Am I still able to plant the seeds outdoors in July??
<a title="View user profile." href="/author/editors">The Editors</a> Thu, 07/31/2014 - 08:18

How sweet of your grandmother. Asters are plant that can thrive in Minnesota—and usually bloom in the late summer or fall. They are also a great plant for attracting pollinating bees to the garden late in the season. Normally, you would seed around May though you can set transplants in pots most any time. You can save those seeds in a paper bag in a dry, cool place.

 <span>I<3Gardens</span> Thu, 07/31/2014 - 16:27
So if I already planted them I may be out of luck ? : /