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Asters: The Stars of Your Fall Garden

I have a deep interest in nature, gardening, and sustainability. The local arboretum is my universe of learning, and my garden is my lab!

What Is an Aster?

Asters are one of the many members of the daisy family, as are goldenrods. Asters flower freely if left to their own devices. They have been cultivated into many varieties that look a little tamer than their country cousins, but I am partial to the wilder looking ones.

They are grouped under the plant family Asteraceae. There are about 250 different varieties of these flower types, but basically, they look like delicate daisies. I know goldenrods don't look like asters, but they are also related. Asters, daisies and goldenrods are natives of the United States but also grow in other temperate parts of the world.

Blue Asters Are the Forgotten Fall Flower

Asters are grouped into four main areas: perennials, annuals, biennials and subshrubs. The perennial aster is what I am writing about today, and there are some beauties in this group. These native American flowers are often the overlooked fall flower. While browsing through the ubiquitous mums that seem to pop up everywhere in the fall, keep an eye out for asters.

They are more subtle and simple in form with single rays emulating from a central disc. They arrive in cooler colors including the lightest lilac to white and also include mid-range blues and purples. Blue is an uncommon color in the flower world and you could pair these with the rich oranges and bright yellows of some of the mums. Of all the flowers related to daisies, the resemblance is strongest in asters.

The other fall favorite for gardens, chrysanthemums, are native to Asia, Russia and parts of the Arctic. I mention chrysanthemums (or mums, as they are known) because they are everywhere starting in late September and people forget about asters.

Growing Conditions

Their growth habit is variable, sometimes branching out and sending sprays of star-like flowers in all directions, which other cultivars grow in tame mounds. When I see asters, they remind me of late-summer evenings long ago when I would spot these bright little patches of unexpected daisy-like flowers in a field or by a roadside. I especially loved the blue-purple ones.

Most like full sun but not boiling hot. So if your summers are super hot you may want to give them a break and place them in a spot with some afternoon shade, under another less dense plant so the sun can still get through, or next to a large rock. They enjoy tumbling over large flat rocks and planting them near rocks keeps the asters cool by protecting their roots. They are perfect in a rock garden. Asters will come back every year if planted properly. The cool purple and blue hues are an excellent contrast to the many yellows and golds of the fall landscape.

The dried seed heads are interesting themselves. They are tan to gold in color and look like aged miniature stars. As you may know from reading prior articles, I am equally interested in the garden out of bloom in its more subtle moments. All seasons have their time of beauty.

Thanks to asters bees can feed themselves well into the fall.

Thanks to asters bees can feed themselves well into the fall.

Aster Varieties

  • Heath Asters: These look the wildest and the plants have hundreds of small white flowers, some with burgundy centers. The flowers grow all along their stems.
  • Heart Leaf Asters: As always, there is an exception to the rule. These asters have dark center discs and lighter purple rays emanating from the center.
  • Calico Asters: Very similar to Heath Asters but the flowers only bloom on one side of the stem, where heath asters bloom all the way around the stem. Another wonderful quality of calico and heath asters is that their central disc is large compared to their petite flower rays.
  • New England Asters: Botanical name novae-angliae, these usually come in purple-blue or light pink hues with golden yellow centers. The flowers are about 1 and 1/2 inches across and these have an upright habit and grow up to 6 feet high. New England Asters are big and colorful so they would probably do well as an informal privacy screen when in bloom or at the back of a perennial garden border. Very good for flower arranging as the stems are sturdy.
  • New York Asters: Botanical name novi-belgii, these are somewhat smaller at a height of up to 4 feet but are also excellent bloomers with some beautiful blue varieties. Their stems are thinner than New England Asters and their leaves are smooth. There is also one gorgeous cultivar called Crimson Brocade with crimson red rays and bright yellow centers.
  • Red Asters: Yes, there are red asters and they are as striking as their blue counterparts. They would fall under the New York Asters—novi-belgii. These asters are really rich-looking. They are a crimson color, a red with slightly cool undertones, with cheery yellow centers that grow to about 3 feet high. A nice compact, gorgeous flower.
'King George' found in the sub group Aster amellus are light blue asters. Blue is a rare color in flowers.

'King George' found in the sub group Aster amellus are light blue asters. Blue is a rare color in flowers.

Aster Care

Asters like a sunny spot and a slope is a good home for them because some varieties tend to get rangy. The slope keeps them in check and allows them to take advantage of their naturally rambling nature and their need for good drainage.

Potted Asters

If you are transplanting a potted aster, dig the hole slightly deeper than the pot but about two and 1/2 times as wide so the roots can spread. Take the plant out of the container by turning the container upside down, tap the bottom and squeeze the sides slightly so the plant will slip out. Don't pull it out, let it gently drop out. Loosen the compacted roots at the base of the plant and them place in the hole you dug. Water slowly and deeply, wait a couple of minutes until all the water looks absorbed then repeat.

Potted plants dry out very quickly. You don't want to overwater them once established. But, when you first plant them, give them a nice long drink. For the first couple of weeks water them once a week, but thoroughly at the base, not overhead. This will allow the roots to get established in their new home.

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Planting Asters From Seeds

If you have collected seeds from the previous year, early spring would the time to plant them to allow themselves to get established. You can start them in a cold frame which is simply a frame with no bottom, solid sides and a clear vinyl or plastic top to catch and retain heat. Place seeds in good garden soil in the frame, but make sure the cold frame is in a sunny spot allowing this small microclimate to store heat. This will promote sprouting of the seeds and can take about ten days.

Usually, you can put your cold frame out in late March but I would wait until April to plant the aster seeds. The sun will warm up the earth during the day prompting the seedlings to sprout. At night, depending on how low the temperature goes, you may want to drape a blanket over the top to retain the heat the seedlings gained during the day. Being out in a cold frame encourages strength and rapid growth in the seedlings. Don't spoil them, but don't let them suffer either. Shelter the cold frame from ferocious spring winds and dropping temperatures. Spring is one of the most unpredictable seasons.

These are the asters I used to spot in open fields and roadsides.

These are the asters I used to spot in open fields and roadsides.

Propagating Asters

Asters tend to get a little straggly. They are a native wildflower after all. When the middle looks as if it is dying off, it is time to divide them.

Propagation can be done in two ways:

  • Taking root cuttings
  • Division

Taking Root Cuttings

Cut everything off of the shoot except for a couple of leaves towards the top and put the cutting in a container with sand and perlite. For those who do not know what perlite is, it is a volcanic glass that has been superheated until it pops like popcorn into the little puffs you see in some potting soils. The beauty of perlite is that it attracts and holds moisture on the outside of each puff and cuttings absorb this moisture which encourages new root growth. Make sure to moisten the perlite before mixing with sand, then put a plastic bag over the top.

Within a couple of weeks, you should see new roots. When the roots are about 2 inches long plant the cuttings in the ground. When taking the cutting from the parent aster, make sure it is a young shoot. You will be able to tell this because the leaves will look extra fresh and a lighter color of green. Periodically check to see that the perlite/sand mixture is still moist and keep the cutting in bright light, but not direct light. Timing is important. Take the cutting in spring or early summer but no later than that. The new fledgling plant needs time to establish itself.


The other way is by division. You would either lift the entire plant in the spring and cut through the plant at natural separations and include side shoots and roots then replant. Or don't lift the entire plant. If it still looks good in the middle, just take some side cuttings, but do cut right down into the soil to also include some of the root systems and replant.

Water thoroughly and check every 3 or 4 days to make sure new plantings have not dried out. Plant asters about 18 inches apart and don't crowd them in with other plants. Plant in a sunny location and by fall you will have some more asters to fill your world.

Asters enjoy nestling among rocks and make great rock garden additions.

Asters enjoy nestling among rocks and make great rock garden additions.

Blue Asters

With so many colors other than shades of blue in our gardens, it is refreshing to plant moments of blue with asters. Although they do come in shades of red along with the lightest lilac, pinks, purples and white, I am always delighted when I see our native blue wildflower growing happily in our gardens.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2017 Claudia Smaletz


Claudia Smaletz (author) from East Coast on October 24, 2017:

Hi Chitrangada and thank-you for reading my article. The world of plants endlessly fascinating to me as I am sure you tell.

Chitrangada Sharan from New Delhi, India on October 24, 2017:

Beautiful Asters with lovely colours!

Very interesting and informative article about these gorgeous flowers. I have always admired their beauty, but didn’t know so many details about them.

Thanks for sharing this wonderful information!

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