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How to Grow Aster Flowers

Learn how to grow aster flowers, the perfect fall-blooming perennial pollinator that also looks good all spring and summer!

Learn how to grow aster flowers—a perfect fall pollinator!

Asters are now one my one of my favorite fall-blooming perennials. And I kind of fell into this one by accident. When I decided to focus on perennials and pollinators for the first year of our new home’s back garden, my strategy was kind of shooting in the dark.

I went to a local nursery that has all of their perennials labeled by light needs, if they are good pollinators, their size, by when they bloom, and by if they make good cut flowers.

I chose aster because the little purple-blue flowers were lovely. But mostly because the variety I got—aster oblongifolius “Raydons Favorite,” aka aromatic aster–grows to be about 3 feet tall and wide. And makes a lovely anchor piece in the garden!

large aster plant filled with purple-blue flowers
white aster flowers

Where do asters come from?

Aster is actually the name for a genus of around 170 species of perennial flowers. According to Wikipedia, all but one of the species are restricted to Eurasia. However, these lovely plants grow as perennials in U.S. grow zones 3, 4, 5, 6, 7, 8, and 9.

There are different types of aster plants. And they produce blue, purple, periwinkle, red, pink, and white star-shaped flowers. In fact, the name “aster” comes from the Greek word for star.

All of them have a rather delicate look to them with small petals and yellow centers. And according to some sources, they are the birth flowers for people born in September. (Although others say September is morning glories? I don’t know. I’m a Scorpio.)

light pink aster flower

Do asters come back every year?

Yes! They do. In a variety of grow zones. I’m in zone 7, and I planted a tiny aster in early spring. It absolutely exploded in size through the summer. I didn’t do any pruning, but I did stake the plant to help it grow straight.

My plants looked lovely all summer even without flowers…though they did throw out the odd flower here and there. The fine green leaves looked lovely as a backdrop for my color-filled annuals.

For spring-blooming perennials, check out my guides on How to Plant Tulips, How to Grow Allium, and How to Grow Hyacinth Flowers!

purple-blue aster flowers

How long does it take for an aster to grow?

In my experience, aster grows quite quickly. Specifically, my “Raydons Favorite” variety grew like an absolute weed. After planting, it grew to be about 6 times the size of when I planted it. 

Here’s a look at the size when I planted it below…and then a few months later. In just a few months, I’d say it reached its full size—though I’ll probably do a bit of pruning next year just to control its shape.

starter garden in the spring with a small aster plant circled
starter garden in the spring with an arrow pointing to an aster bush

Do asters bloom more than once?

Yes, aster blooms in the late summer or early fall (depending on the variety) every year. While mine threw out the occasional bloom during the summer, I noticed it just totally exploded with blooms one day in October.

Even after two frosts, the blooms looked amazing. Such a welcome addition to a fall garden where everything is dying!

large white aster flowers

Should asters be cut back after flowering?

You don’t need to deadhead aster flowers after they bloom since they bloom at the end of the growing season. So “after flowering” and the end of the season are actually the same time.

When the flowers die off, you can cut all of the stems down to a few inches above the ground. If you don’t cut them back, you might end up with seeds that can drop into the soil and spread.

pink aster flowers

Do aster plants spread?

And on that note, aster plants can spread by seed. So it’s best to prune them back as soon as the plant is done flowering. However, if you want them to spread…have at it!

Leaving the stems un-pruned at the end of the growing season can result in the dead flower heads dropping seeds, which will sprout in the spring.

Do asters like sun or shade?

If you’re looking for the best place to grow aster plants, shoot for full sun. I have mine in some of the sunniest spots in the garden. However, the plant can also tolerate part shade. It may bloom less prolifically, though.

purple-blue aster flower
white aster flowers

Is aster a good plant for butterflies?

In addition to being pretty, aster flowers are also food for a bunch of Lepidoptera species (an order of insects that includes butterflies and moths). And they bloom in a time when there aren’t many other pollinators blooming, so they make a lovely late-season snack.

Want the perfect pollinator partner for your aster plants? Check out my posts on How to Grow Beautiful Zinnia Flowers and How to Harvest Zinnia Seeds.

monarch butterfly on pink aster flowers

How to plant aster plants

Asters do not like super hot days. I did notice that the leaves on mine yellowed a bit in the peak of our hottest summer days. But the plant rebounded very well once temperatures dropped a bit.

When I planted my aster plants, I dug a hole about twice the size of the plant’s root ball. Then I put in a shallow layer of leaf compost and set the plant in. I backfilled the plant using a mixture of the dirt I dug out and leaf compost.

The leaf compost helps to lighten up the soil, making it a bit more well-draining. It also improves the overall quality and adds nutrients. Our soil sucks.

I didn’t need to prune my plants at all as I was very happy with how they grew. However, I may trim them to control their shape next spring or summer—we’ll see.

white aster flowers
large aster plant filled with purple-blue flowers

Is aster hard to grow?

I’d say absolutely no. I barely gave mine any attention all spring and summer, and they did great! Giving them a great base with leaf compost and a solid layer of mulch at the surface helped, I think.

We get some deep, soaking rains over the spring and summer where I live. However, if it was super hot (90+ Fahrenheit) and we went more than 48 hours without rain, I’d give my garden a solid soak with the hose.

Is aster poisonous to dogs?

Aster is not known to be poisonous to dogs, other pets, and humans. However, it isn’t a plant grown for consumption. So it’s best not to ingest it.

purple-blue aster flowers

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collage that says how to grow aster flowers with images of blue, purple, pink, and white asters

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