Aster thomsonii (Thomson's aster) — Clump-forming, upright to bushy

Overview

Aster thomsonii is a clump-forming, upright to bushy perennial in the genus Aster, part of the Asteraceae family, with deciduous; simple, often narrow and roughly textured foliage. Aster thomsonii grows best in full sun, and tolerates fertile loam; avoid thin and dry soils soils and neutral to slightly alkaline pH. Its UK hardiness is rated H6–H7. Suggested uses include borders, wildflower gardens and naturalistic plantings. It is native to Pakistan and West Himalaya.

About

Aster thomsonii is a clump-forming perennial in the Asteraceae that flowers from August to October. It grows upright to well-branched stems with deciduous, often narrow and roughly textured leaves. Give it a sunny spot in fertile, moisture-retentive loam and avoid thin, dry soils. It suits south, east or west-facing sites and will tolerate exposed as well as sheltered positions.

About the genus

Aster is a genus of perennial flowering plants in the family Asteraceae. Its circumscription has been narrowed, and it now encompasses around 170 species, all but one of which are restricted to Eurasia; many species formerly in Aster are now in other genera of the tribe Astereae. Aster amellus is the type species of the genus and the family Asteraceae.

Wikipedia contributors, "Aster (genus)", CC BY-SA 4.0 — Aster (genus)

In the garden

Aster thomsonii originates from Pakistan and the West Himalaya and brings a late-summer to autumn flowering period to the garden, with blooms from August to October. As a clump-forming perennial in the Aster genus, it carries narrow, roughly textured leaves that die back seasonally and produce upright to well-branched flowering stems. Choose a full sun site on fertile loam that holds some moisture but drains freely; avoid planting into thin, dry soils. Soil should be neutral to slightly alkaline. The species is rated H6–H7 (very hardy to fully hardy) in the UK and also corresponds to USDA zones 4–8, so it will survive normal winter conditions and can be grown in exposed situations as well as more sheltered spots. Use Aster thomsonii in back or middle of mixed borders, naturalistic plantings and wildflower-style beds where late-season colour is wanted. Its clump-forming habit provides structure through the growing season, and because the foliage is deciduous the clumps renew from the base each year, leaving room for fresh spring growth and companion plants that emerge later.

Growing conditions

Best soil and position for Aster

Sunlight: Full sun
Soil type: Fertile loam; avoid thin, dry soils
Soil pH: Neutral to slightly alkaline
Soil moisture: Moist but well drained
Aspect: South, east or west facing
Exposure: Exposed or sheltered
UK hardiness: H6–H7

Plant details

Aster thomsonii size, habit and characteristics

Plant type: Perennial
Habit: Clump-forming, upright to bushy
Foliage: Deciduous; simple, often narrow and roughly textured
Suggested uses: Borders, wildflower gardens, naturalistic plantings
Native to: Pakistan, West Himalaya

Care notes

Pruning and caring for Aster thomsonii

Cultivation: Plant in an open, airy position — crowding is what brings on mildew. Divide every second or third year to maintain vigour, and pinch or Chelsea-chop the taller kinds in late spring to reduce the need for staking.
Pruning: Deadhead to prolong the display, then cut stems to the base after flowering, or leave them standing through winter for structure and wildlife.
Propagation: Divide in spring, replanting only the vigorous outer growth. Basal cuttings taken in spring root readily.
Pest resistance: Slugs may take young shoots in spring; otherwise generally trouble-free.
Disease resistance: Powdery mildew is the main weakness, especially among the older novi-belgii cultivars. The frikartii hybrids and the aster relatives are markedly more resistant.

Frequently asked questions

How do I grow Aster thomsonii?

Plant in an open, airy position — crowding is what brings on mildew. Divide every second or third year to maintain vigour, and pinch or Chelsea-chop the taller kinds in late spring to reduce the need for staking.

Where is the best place to plant Aster thomsonii?

Aster thomsonii prefers full sun. It suits exposed or sheltered positions.

What soil does Aster thomsonii need?

Aster thomsonii grows best in fertile loam; avoid thin and dry soils soil. It prefers neutral to slightly alkaline soil. Aim for soil that stays moist but well drained.