Symphyotrichum cordifolium
(previously known as Aster cordifolius)
Overview
Uses: Woodland gardens and shaded borders, understory planting at the edge of trees, naturalized woodland-edge and meadow plantings, pollinator gardens, mass planting under high shade.
Benefits: One of the few asters that flowers well out of full sun, carrying clouds of small pale blue daisies on airy branched stems long after most perennials have finished. Heart-shaped basal leaves form a tidy mound in spring, and the late bloom feeds bees and migrating butterflies well into autumn.
USDA Hardiness Zones: 3–8
Sun: Full Sun to Partial Shade
Life Cycle: Hardy Perennial
Growth Habit: Upright, Clumping — airy branched stems above a leafy base
Bloom Color: Blue and Lavender
Mature Height: 2–4 ft.
Mature Width: 1.5–2.5 ft.
Bloom Season: Late summer through fall
Growth Rate: Moderate
Summary
Most asters want open sun. This one grew up at the edge of the eastern woods, and it flowers in the half-light under high trees where the fall garden usually runs out of ideas.
The spring growth is a low mound of heart-shaped leaves, easy to overlook. Through summer the plant builds a framework of thin, wiry, well-branched stems, and then in late summer it opens — hundreds of small daisies, pale blue to soft lavender with centers that start pale yellow and age to dusty rose. From a distance the effect is closer to a mist than to individual flowers.
It is one of the last things blooming in a shaded garden, which matters more than it sounds. Late nectar is scarce, and this aster draws bumblebees, small native bees, and migrating butterflies through weeks when there is little else for them.
Care
Blue Wood Aster Care
Plant in full sun to partial shade. It takes more shade than any other aster commonly sold, and in hot southern gardens some afternoon shade actually improves it. Plants in deeper shade grow looser and flower a little less heavily, which many gardeners prefer in a naturalized setting.
Average, well-drained garden soil is enough. It handles the dry, root-filled ground under mature trees better than most perennials, but it will not sit in soggy winter soil.
Water through the first season while roots establish, then only during extended dry spells. Established plants are fairly self-sufficient.
Feeding is rarely needed and rich soil produces floppy stems. If growth is genuinely weak, one light spring application of slow release fertilizer is plenty.
For a denser, shorter plant, cut stems back by about half in early June. Leave the seed heads standing through winter for the birds and cut the whole plant to the ground in early spring. Deadheading before seed set reduces self-sowing if you want to keep it in bounds.
Size
What Size is the Blue Wood Aster for Sale Online?
Our Blue Wood Aster ships in a greenhouse-grade grow pot and is appropriately sized for its container at the time of shipment. If you have specific sizing or planting questions, please contact us.
How Large Does Blue Wood Aster Grow?
Blue Wood Aster reaches two to four feet tall in bloom and spreads about a foot and a half to two and a half feet wide. Plants in shade run taller and looser; plants in sun stay shorter and denser. Space eighteen to twenty-four inches apart for a drift.
Additional Information
What are some common names for this plant?
The most widely used names, in rough order of familiarity, are:
- Blue wood aster
- Heart-leaved aster
- Common blue wood aster
- Bluewood aster
Why is the botanical name different from what I remember?
It was long sold as Aster cordifolius. Botanists split the North American asters out of the Old World genus Aster some years ago, and this species moved to Symphyotrichum. Nothing about the plant changed — only the name. Both are still in common use in the nursery trade.
How much shade will it actually take?
It flowers acceptably in about four hours of sun and does well in bright dappled light beneath high-canopy trees. In deep, all-day shade it will persist and stay green but bloom sparsely. Think woodland edge rather than the north side of a building. Browse our Native Plants of North America collection for more shade-tolerant natives.
Does it spread aggressively?
No. The clump widens slowly from the crown rather than running underground. It does self-sow where soil is open, which is welcome in a naturalized planting and easy to prevent in a formal bed by cutting the plant back after bloom. See our Perennials collection for other long-lived options.
Do deer bother it?
Deer will sample it in heavy-pressure areas, particularly on new spring growth, but it is not a preferred target and established plants usually recover without trouble. If deer are a constant problem, see our deer-resistant perennials and grasses.
