These autumn superstars take the stage as summer winds down.
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Asters are the stars of the autumn garden.
Our native asters have been cultivated for hundreds of years, generating the wide variety of cultivars available today.
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Songbirds feasting on seeds carry the charm of these lovely plants into the winter months.
Purple Aster Care
Asters are adaptable plants and easy to grow in average, well-draining garden soil.
Select a planting site with good air circulation to promote healthy foliage.
In hot locations, plants benefit from afternoon shade.
Soil
Asters perform well in loamy garden soils of average fertility.
They perform well in dry or rocky soil.
Most aster species tolerate clay soil.
As a rule, water young plants regularly until established, then irrigate throughout summer during dry periods.
To prevent fungal disease, water at the base of theplant, preferably in the morning.
Temperature And Humidity
Asters tolerate a range of growing conditions.
Plants are winter hardy and stand up to summer heat and humidity.
They bloom best when autumn nights are cool.
For plants growing in nutrient poor soil, apply a balanced fertilizer in spring.
Both species are native to moist eastern forests andmeadows and perform well in more northerly stretches of the Southeast.
Gardeners in hotter and drier areas might turn to some of the other native asters featured here.
‘Purple Dome’ is a long-time favorite, topping out at 2 feet tall.
This species is well suited to gardens in the upper South (zones 5-8).
Many cultivars are available with flowers ranging from soft pink to rich purple.
With lovely blue-green foliage, ‘Bluebird’ is a popular cultivar that stands 3 to 4 feet tall.
Compact cultivars include ‘Raydons Favorite’ and ‘October Skies’.
Hardy in zones 4-8, these adaptable asters tolerate drought and clay soils.
Not to be confused with blue wood aster,Symphyotrichum cordifolium, an upland forest native.
Native to sandhills and pinewoods in zones 6B-11, this unusual aster is tough as nails.
The rich violet-blue flowers are produced along upright stems standing 2-3 tall.
Prepare the planting bed by adding a thin layer of compost and raking the soil surfacesmooth.
If starting seeds indoors or in outdoor containers, use a high-quality seed starting soil mix.
Look for a container about 3 to 4 inches deep with drainage holes in the bottom.
Use a mister or spray bottle to keep the soil moist but not wet.
Seedlings will emerge in 1-3 weeks, depending on species.
Thin seedlings sown in planting beds to a spacing of six to eight inches.
Transplant seedlings grown indoors into the garden or outdoor containers after the threat of frost has passed.
Seedlings grown in outdoor containers can be moved to the garden when they are 3-4 tall.
The same is true for any seedlings you started indoors from seed.
Hardening off slowly acclimates plants to outdoor conditions to avoid shocking them with the drastic change in environment.
Begin hardening off seedlings about one week prior to transplanting outdoors.
Increase the length of time aster seedlings are outside each day and slowly increase exposure to sunlight and wind.
By the end of the week, plants can be set in full sun and left outside overnight.
Pay attention to watering as plants will require more water outside due to wind and higher temperatures.
Space plants according to their mature width, 1 to 3 feet apart, depending on the species.
Dig a planting hole large enough to accommodate the root ball of the plant.
Gently remove the plant from its pot and loosen the roots if they are tightly bound.
Set plants at the same depth they are growing in their containers.
Fill the planting hole with soil, pressing the soil down gently with your hand.
Cut back plants by up to one third in mid to late June.
Do not pinch after early July or you risk removing flower buds.
Many asters grow quite tall and may require staking to keep from flopping over.
Pinching back plants can help reduce the need for staking.
Deadhead plants after flowering if you do not want your asters to self-sow in the garden.
Propagating Purple Aster
Asters can be propagated from seed, cutting, or division.
Plants grown from seed take a long time to reach a sizeable, flowering plant.
Division is the simplest way to multiply plants.
Dividing asters not only produces new plants, but also benefits existing plants and keeps their size in check.
Like other fall-blooming perennials, asters are best divided in spring, rather than fall.
Dig plants in early spring when the ground has thawed and plants begin to break dormancy.
Separate the crown into multiple 6- to 8-inch sections, making sure each portion has roots and shoots.
Replant divisions immediately and keep them well watered to establish.
New plants can also be propagated from cuttings.
Clip 2- to 4-inch sections of young, tender stems in spring.
Remove the cuttings lower leaves and dip the cut end in a rooting hormone.
Mist plants as needed to maintain soil moisture.
Cuttings will root within a few weeks.
New plants can be hardened off and planted outdoors in fall.
Severe infections can cause foliage to drop from plants.
Good air circulation helps reduce the incidence of powdery mildew.
Improve air movement through the plant canopy by spacing plants farther apart and selectively thinning branches as appropriate.
The best way to avoid powdery mildew is to plant disease-resistant varieties.
Smooth aster cultivars like ‘Bluebird’ and ‘Calliope’ have excellent mildew resistance, as do aromatic asters.
The Woods series asters also have good disease resistance.
Seek out varieties with proven resistance.
