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Symphyotrichum chilense (Pacific Aster)
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© Erica Fleniken, some rights reserved (CC-BY-NC) · iNaturalist

Symphyotrichum chilense

Pacific Aster

At a Glance

FoliageDeciduous
Height1-3 feet (30-90 cm)
Width1-3 feet (30-90 cm)
Maturity3 years

Growing Zones

USDA Hardiness Zones

7 - 10
These zones indicate the coldest temperatures this plant can typically survive.
What's my zone? →
Frost Tolerancehardy

Overview

Symphyotrichum chilense is a herbaceous perennial reaching 1-3 feet (30-90 cm) tall and 1-3 feet (30-90 cm) wide, forming colonies from spreading rhizomes. Stems are slender, slightly hairy, and often branched in the upper half. Leaves are linear to lance-shaped, 1-4 inches (2.5-10 cm) long and 0.25-0.5 inch (6-12 mm) wide, with smooth or sparsely toothed margins; basal leaves wither by bloom time. Composite flower heads 1-1.5 inches (2.5-4 cm) across appear in loose, branched panicles from July through October, with peak bloom from August through September. Each head has 15-30 pale violet to blue-violet ray florets surrounding a yellow disc that ages to reddish-purple. Each flower head lasts 5-10 days; total bloom on a single plant extends 6-10 weeks. Achenes 0.1 inch (2.5 mm) long with whitish pappus mature October through November and disperse by wind. Foliage dies back to the rhizome after the first hard frost in zones 7-9. Spreads by rhizomes 6-12 inches (15-30 cm) per year, forming colonies 3-6 feet (90-180 cm) wide over 3-5 years. Lifespan 8-15 years for individual stems; rhizome systems persist longer. Tolerates salt spray and brackish soils, suiting the species to coastal sites.

Native Range

Native to coastal grasslands, dune meadows, salt marsh edges, and bluff openings from southern British Columbia south through coastal Washington and Oregon to central California. Restricted to sites within 5 miles (8 km) of the Pacific coast at elevations from sea level to 500 feet (150 m), with salt-spray and saline-soil tolerance throughout the range.

Suggested Uses

Used in coastal native plant gardens, late-season pollinator borders, dune restoration plantings, and bioswales. Spaced 18-24 inches (45-60 cm) apart in groupings of 5-9 plants. Functions as a nectar source for migrating monarch butterflies in coastal corridors and as a host plant for larvae of the pearl crescent and several other checkerspot butterflies.

How to Identify

Slender stems 1-3 feet (30-90 cm) tall with linear to lance-shaped leaves and pale violet to blue-violet flower heads 1-1.5 inches (2.5-4 cm) across. Distinguished from S. subspicatum by branched (not raceme-like) inflorescence and coastal habitat. Distinguished from S. novi-belgii by narrower, smaller leaves and consistently smaller flower heads.

Appearance

Size & Dimensions

Height1' - 3'
Width/Spread1' - 3'

Reaches mature size in approximately 3 years

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~10 weeks
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Flowers from July through October across the range, with peak bloom from August through September in zones 7-9. Cool maritime conditions can extend bloom into early November. Each flower head lasts 5-10 days; total bloom on a single plant extends 6-10 weeks.

Detailed Descriptions

Flower Description

pale violet to blue-violet with yellow center

Foliage Description

medium green

Growing Conditions

Sun Requirements

Requires 6-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)
357912
Soil Types
Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

2-3 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Plant container-grown stock or sow seed in fall in well-drained sandy or loamy soils with full sun to light shade. Water during the first growing season; established plants tolerate seasonal drought of 4-6 weeks. Tolerates salt spray, brackish soils, and sandy substrates, suiting coastal exposure. Powdery mildew may develop on lower foliage in humid summers; pruning the lower one-third of stems in midsummer reduces incidence. Spreading rhizomes can extend beyond intended planting areas and may need root barriers in confined garden beds. Crowns benefit from division every 3-4 years in early spring as new shoots emerge.

Pruning

Cut spent flowering stems to the base in late fall after seed has dispersed, or leave in place through winter for songbird forage. Pinch growing tips at 6-8 inches (15-20 cm) tall in late spring to encourage branching and reduce stem flop in fertile soils. Divide every 3-4 years in early spring.

Pruning Schedule

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summerfall

Maintenance Level

low

⚠️ Toxicity Warning

Non-toxic