Aromatic aster

Sun

Full sun; tolerates light shade but flowers less and may become floppy.

Water

Low to moderate once established; water regularly during the first growing season.

Soil

Well-drained sandy, gravelly or loamy soil; tolerates clay if drainage is good. Accepts mildly acidic to alkaline conditions and does not need rich soil.

Height

1-3 ft (0.3-0.9 m)

Spread

1-3 ft (0.3-0.9 m), widening over time

Flowers

Late summer through autumn; violet-blue to lavender rays around yellow centres that age reddish-purple.

Foliage

Small, oblong green leaves on densely branched stems; the leaves release an aromatic scent when crushed.

Growth

Moderate

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Cold hardy
• Wildlife
• Low allergen
• Fragrant

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   1.3 ft (0.4 m)

3. After 2 years

   1.6 ft (0.5 m)

4. After 3 years

   2 ft (0.6 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

the US

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Moderate

• Water newly planted clumps deeply whenever the root zone starts to dry; established plants need extra water mainly during prolonged drought.
• Avoid routine feeding in ordinary garden soil; rich soil and excess nitrogen encourage floppy growth.
• Keep mulch clear of the crown, especially where winters are wet.
• Divide congested clumps in spring every three to four years, or when flowering declines.
• Remove unwanted seedlings and dig out spreading shoots where space is limited.

Pruning. For shorter, denser plants, shorten stems by about one-third in late spring or early summer, before flower buds form. Leave spent stems through winter for wildlife, then cut them close to ground level in early spring before new growth develops.

Early spring

Cut back old stems, leaving any occupied hollow stems nearby for emerging insects.

Spring

Plant or divide clumps and water thoroughly.

Late spring

Optionally shorten shoots by one-third to encourage compact growth.

Summer

Water young plants during dry spells and check shaded or crowded plants for mildew.

Autumn

Leave flowers for pollinators; remove spent heads before seed ripens only if seedlings are unwanted.

Winter

Leave stems and seedheads standing, and check that water is not collecting around the crown.

• Plant in drifts with little bluestem and prairie dropseed for a low, late-flowering meadow effect.
• Use at the front or middle of a sunny border with coneflowers and black-eyed Susans to extend the flowering season.
• Repeat clumps through a gravel garden for autumn colour without frequent irrigation.
• Place beside a sunny path where its flowers can be seen closely and its foliage brushed lightly.

Garden styles it suits: Native meadow, New perennial (prairie), Pollinator garden, Dry gravel garden, Cottage garden and Autumn colour.

Plant it with: Little bluestem, Prairie dropseed, Purple coneflower, Black-eyed Susan, Butterfly weed and Showy goldenrod.

Wildlife: Flowers provide late-season nectar and pollen for bees, butterflies and other insects. Seedheads may feed small birds, and standing stems provide overwintering shelter for insects.

• Powdery mildew can affect crowded or shaded plants: increase sunlight and airflow, divide dense clumps and avoid drought stress.
• Root or crown rot in waterlogged soil: improve drainage or move the plant to a raised position rather than watering on a fixed schedule.
• Floppy stems in shade or rich soil: move to full sun, stop nitrogen feeding and shorten shoots in late spring.
• Lace bugs can cause pale stippling on leaves: inspect leaf undersides and use insecticidal soap if damage is substantial, avoiding open flowers and visiting insects.

Not known to be toxic to people, cats, dogs or horses; no particular part is recognised as poisonous. Species-specific safety information is limited, so do not treat it as an edible plant or encourage pets to eat it.

• New England aster (Symphyotrichum novae-angliae)

  Usually taller, with conspicuously hairy stems and leaves whose bases clasp the stem; aromatic aster is generally lower and bushier, with smaller, non-clasping, aromatic leaves.

• Smooth aster (Symphyotrichum laeve)

  Has smooth, often blue-green leaves with clasping bases and a more upright habit; aromatic aster has smaller, rougher leaves with a noticeable scent when crushed.

• Heath aster (Symphyotrichum ericoides)

  Usually carries many smaller white flowers and very narrow, heath-like leaves, rather than the broader leaves and larger violet-blue flowers of aromatic aster.

The epithet oblongifolium refers to the oblong leaves, while the common name describes their scent when crushed.

Propagation. Divide clumps in spring or take basal shoot cuttings in spring. Sow seed outdoors in autumn, or give spring-sown seed a period of cold, moist stratification; seedlings may differ from named cultivars.

Accepted botanical name

Symphyotrichum oblongifolium

In the US and Canada

Native in the lower 48 states.

Native range

Alabama, Arkansas, Colorado, Illinois, Indiana, Iowa, Kansas, Kentucky, Maryland, Mexico Northeast, Minnesota and Mississippi.

Measured

Average height 43 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.