How to Plant, Grow, and Care for Douglas Asters

Douglas asters pop up around the same time that goldenrods do. You’ll see purple-yellow aster-like blooms alongside large yellow flower spikes of goldenrods. Both of these native species attract pollinators like butterflies and bees, and they help local insect species that need resources. 

When you plant perennials like Douglas aster, you invite animals to return where they once were. Flowers lure bugs, bugs lure birds, and birds lure larger predatory animals. You feed the local food web by simply planting native flowers. This radical act will make your garden look gorgeous and boost your confidence as a naturalist.

What Is It?

Douglas asters are native wildflowers of western North America. Although aster is a part of their name, they are not true asters of the Aster genus. They’re a part of the Symphyotrichum genus, which includes other North American asters like Michaelmas daisy and leafy aster. 

These New World asters work better in our landscapes than non-native ones, as they appeal to the insects and animals that live on our continent. Consider subbing marginally hardy and non-native asters for gorgeous, frost-tolerant, and tough native species. 

Native Area

Douglas asters are close relatives of New York asters and Michaelmas daisies. The western species grows from Alaska southward through California, and east to Montana and Idaho. It prefers sandy sites near bodies of water, forests, and open meadows. Find the plants growing where Canada goldenrods are, as the two prefer similar conditions.

I often see this perennial poking out of the sand near the Willamette River by my home. It sprouts where the trees let sunlight poke through. The ample moisture near the riverside allows the roots to creep into new locations underground while the stems sow seeds aboveground, giving the plants two chances at spreading. 

Characteristics

Douglas aster plants are leafy perennials with many qualities similar to European asters and daisies. They sprout hairy stems early with lance-shaped leaves. The leaves often have small teeth on the edges, and their tops and bottoms are hairless and green. 

This North American aster reaches between 8 and 32 inches tall, although it sometimes grows taller and leggy if it doesn’t receive enough sunlight. In late summer through late autumn you’ll see dozens of flowers open up on the stem tips. They have purple-blue petals and sunshine-yellow composite centers. 

Each composite center contains dozens of tiny flowers that form heads with multiple seeds after successful pollination. Leave the stems and seed heads and they’ll feed hungry birds throughout the winter. In cold zones with winter chill, this perennial dies back to the soil level. New sprouts emerge in spring as days lengthen and temperatures warm.

Planting

Because this is a tough perennial wildflower, getting it into the ground is simple. Your specimen will take off with new root growth shortly after planting and likely bloom this year. Seedlings may take longer to blossom and most likely will flower in their second year after growing successfully. Start seeds if potted plants are unavailable; otherwise, it’s easier to plant mature specimens from containers. 

Growing from Seed

Like many other native plants, Douglas aster seeds grow best when you plant them during fall a month or two before your first hard frost. You may also sow seeds in early spring, although fall sowings have a higher chance of blooming in their first year because they germinate sooner than spring ones. 

Cover the tiny seeds with a thin layer of soil and water the site well. Fall sowings may germinate and overwinter, or they’ll sprout in early spring when native seedlings start growing in natural environments. Thin overcrowded seedlings so there’s four or six inches between them.

You may also start seeds indoors if you’d prefer to have more control over the sprouts. Plant them in small 4” paper pots and layer a thin coating of soil on top. Keep them warm, moist, and lit while they germinate. Transplant the plants outdoors after the danger of frost passes in spring. If you sow seeds in summer, plant the mature seedlings a month or two before your first hard frost of fall. 

Transplanting

Transplanting seedlings or potted plants is easy enough with the right materials. You’ll need: 

Start the transplanting process by digging a hole as deep and twice as wide as your plant’s rootball. Remove the aster from its container, and loosen the roots so they dangle downwards. Place the plant into the hole so it sits at soil level, then backfill the empty hole with the loose soil you dug out. 

Add compost or mulch on top of the soil to protect the new transplant, then water the site well. Your specimens will take off in no time—they may produce dozens of flowers by late summer!

How to Grow

This native perennial is one of the easiest garden plants to grow on the western side of North America. It thrives with little care once it establishes itself. Grant Douglas aster what it needs while it’s young and you’ll have dozens of rooting stems popping up in your garden a year later. 

Light

Douglas aster enjoys full sun, meaning it’ll thrive with six to eight hours of direct sunlight. It will also function well in partial shade, although it’ll have fewer flowers than other plants with full sun. 

The more sunlight the plant receives, the more water it’ll require, and the more blooms it’ll produce. Modify your care techniques to match what your plant needs so it survives droughts and floods. 

Remember, this native wildflower grows near streams and forests in well-draining soil. Areas near bodies of water often have lots of direct sunlight with ample water, while forested sites have dappled sunlight and less moisture. Match the native plant’s preferences in your garden and it’ll resist undesirable environmental pressures. 

Water

Douglas asters have varying water needs depending on where they grow. Give them ample water during the growing season if they receive full sun and less moisture if they’re in partial shade. They’ll tolerate summer droughts and fall or winter flooding, making them ideal perennials for sites with changing moisture levels.

These North American native plants naturally enter dormancy as frosty weather arrives. They stay safe underground in rhizomatous roots below where the dirt freezes. Keep them moist but not soggy throughout their dormancy. They’ll have additional frost protection when under snow, mulch, or compost. The layer acts like a blanket and safeguards your perennials from extreme storms. 

Soil

This plant thrives in well-draining soil rich in organic matter. It’ll tolerate sandy sites, as it naturally grows in some areas of the West Coast. If your garden is thick with clay or silt, consider amending it with sand and organic matter to break up the chunks. This will help guarantee your plant’s success in the long run. 

These perennials grow in the forest, but the forests often have a layer of duff that’s loose and airy for their roots. Try to emulate loose, crumbly conditions in the garden to set this native plant up for success.

Fertilizing

Douglas asters are low feeders, and they typically thrive in the soil you plant them in. A good rule of thumb is to add one or two helpings of organic matter each year. Use compost, leaf mold, or fall leaves to form a layer two to three inches thick above the dirt. This layer will decay slowly to add small increments of nutrients your plants soak up. 

Excess fertilizers may cause growing issues rather than boosting your plants, so use small amounts of organic fertilizer if necessary. You can apply a helping or two annually, using a half or quarter dose according to the package’s instructions. 

Maintenance

This garden ornamental has little maintenance. Leave the dead stems throughout the winter instead of pruning them. They’ll feed small birds with their seeds, and the dead stems protect sensitive sprouts below the soil. 

One main task you’ll have is limiting this plant’s growth! It’ll spread underground with creeping roots and on top of the soil through germinating seeds. Pull up seedlings and dig up rooted rhizomes. Plant them where you’d like, or throw them in a compost pile to recycle them. 

Propagation

Try any of these three methods for easy propagation. Seed saving is simple but less reliable than cuttings or divisions. Cuttings and divisions work well, although they require mature plants. Use whichever method is easiest for you and your garden’s setup.

Seed Saving

All you need to save seeds is a flowering Douglas aster! Let it flower outdoors, watch as pollinators flock to the blossoms, then wait for seeds with fluffy plumes to form. Like dandelion seed heads, those of asters have feathery attachments so they can waft in the wind to new locations. 

Save seeds by plucking these plumes from the stems in late fall. They should pull seeds right out of the heads. Let them dry, then decide whether you’ll sow or save them. Sow them immediately after collecting them for fall plantings. Store them in an airtight container in a cool, dark, and dry location if you’d prefer to sow them in spring. 

Cuttings

Cuttings are a great propagation tool during spring or summer, and year-round indoors. Snip four to six-inch stem pieces off the mother plant, then strip each of its lower leaves. Place the stripped cuttings in pots with free-draining potting soil and water them well. 

Your cuttings need bright indirect sunlight or partial shade and consistent temperatures to root successfully. A cactus or succulent soil mix works well, as it allows you to give your plants consistent moisture while ensuring they don’t grow soggy and rot. 

The cuttings will form roots four weeks or more after planting. Wait until they start putting out new growth to transplant them. You want them to develop a strong root system so they handle the transition without issues.

Division

Division is the most reliable way of propagating Douglas asters. Simply wait for a plant to reach maturity, then dig up a portion of it to move elsewhere. You’ll cause the original plant to sprout new growth, and you’ll have a separate specimen to fill in empty spaces. 

Dividing is best in late fall after Douglas asters finish flowering, or in early spring as they start growing. Use your shovel to sever a portion of the plant underground, then dig it up. Take care to leave the original specimen intact while you remove the cut-off portion. 

Dig a new hole as deep and twice as wide as the division’s rootball. Place it in the hole, and backfill the soil until it covers the roots. Water well, then watch these asters take over your garden with beautiful blooms!

Popular Varieties

There is one species of Douglas aster, Symphyotrichum subspicatum. You may try this species if you live outside its native range, although other similar and more suitable species grow near you depending on where you live. Choose one of the following asters in the Symphyotrichum species according to your growing region:

When in doubt, choose a North American aster that grows in wild spaces near you. It’ll acclimate well to your garden and require little care, water, and maintenance throughout its lifetime. You’ll boost your local environment’s biodiversity by growing these nectar-rich native plants that local wildlife need to survive!

Common Problems

Because this American aster is hardy in its native range, it has few pests or diseases. Its perennial nature prevents most issues from growing out of control, as they’ll die or disappear for the winter. New sprouts emerge in spring with little remnants of aphids or powdery mildew from the past year. 

Pests

The main insect pest of this aster is aphids. They attack the fleshy leaves, flowers, and stems to feed. They gorge themselves full of plant matter and produce tiny babies that eat more of your plants. The good news is they’re easy to remove! Simply hose your plants off daily with strong streams of water. The aphids will disappear in a week or two. 

Diseases

Two main diseases affect these North American asters: powdery mildew and aster yellows. Powdery mildew is a fungal condition that spreads through spores. You’ll see white or gray dust coverings coating your plant’s leaves and stems. It spreads rapidly during fall and spring while wet, warm weather is abundant. 

Powdery mildew is rarely lethal. It’ll hinder your plant’s growth this season at its worst. To control the mildew, use an organic option like potassium bicarbonate or a milk spray. These options prevent the mildew from spreading while avoiding harm to any beneficial pollinators or predatory insects. Prune away damaged areas if you’re dealing with a small case.

Aster yellows is a unique disease targeting plants in many families, although species in the aster family are especially susceptible. It causes weird fleshy growths on the flower heads, and the petals often turn green instead of purple. Flowers distort and grow in a deformed manner. It’s also rarely fatal, although it can spread to nearby plants and it’s uncurable. Remove infected plants to control the spread.

Frequently Asked Questions