Blue Wood Aster or Heartleaf Aster

• Blooms many pale blue flowers in mid-to-late fall.
• Native to a wide region of Eastern North America.
• Very easy to grow; requires little to no care.
• Can tolerate light to moderate shade, but not heavy shade.
• Spreads by wind-dispersed seeds; easy to grow from seed.

The blue wood aster can be grown in full sunlight, but it requires considerably less sunlight than a lot of the more colorful asters.  For example, it is much more shade tolerant than the common purple New England aster.  It will not bloom in heavier shade.  How much shade is too much?  It blooms well in a south-facing exposure, even growing under shade from trees and other plants.  In north-facing exposures, without any direct sunlight during the peak of the day, it blooms well but only if exposed and not if shaded by trees or other plants.

This plant can tolerate a wide range of conditions, but it is more tolerant of drought than moisture.  It will not do as well in soil that is consistently wet.

Its native habitat is open woodlands and woodland edges, and it does particularly well in rich but slightly rocky soils, especially on slopes.

Once established, it requires little care.  It frequently spreads by seed, and will come up elsewhere in your garden.

The blue wood aster can grow upright, but its stems frequently fall over, leading to a sprawling habit.  It often sprawls out as far as 2 feet from the base, in different directions.  The flowers come closer to the end of stems, sometimes leaving it to flower a modest distance from where you planted it.

The initial leaves are largest, and the stems are most likely to be upright earlier in the season.  As the season goes on, the new leaves become smaller, up until when the plant blooms.

Get ready for a lot of blooms!  This plant is a prolific bloomer, and will be covered in lots of light-blue flowers mid-autumn.  Another exciting thing about this plant is the variability of its blooms; if you grow a bunch of plants from seed, you'll find some have thicker rays than others, some have more yellowish flower centers, others more purplish.  The color of blue also varies.

Bees particularly love the flowers of this plant, and are its main pollinators; it attracts a variety of both long-tongued and short-tongued bees.  The flowers also attract wasps, flies, butterflies, skippers, and even beetles.

There are quite a few insects that eat the foliage and other parts of this plant.  The larvae of several butterfly and moth species eat the leaves, and some caterpillars also eat the flowers, seeds, stems, and roots.  The plant also supports leaf beetles, leaf-mining flies, and various true bugs, aphids, and leafhoppers.

Birds, including larger birds like wild turkeys and ruffed grouse, eat the seeds.

The blue wood aster produces numerous small, wind-dispersed seeds.  Left on its own, it will tend to spread, which can be delightful if you like its flowers.  As a relatively small plant, whose denser leaves stay low to the ground, it is unlikely to choke out most other cultivated flowers.  It also tends to be a much more visually-attractive plant, and better for the local ecology, than a number of common weeds in urban and suburban environments, so growing this plant and creating a seed source will be helping to restore and beautify the surrounding ecosystems and gardens.

Because of its prolific seeding, ease of sprouting from seed, and wind dispersed seeds, it is of key importance that you do not plant this plant outside its native range.  It has a high potential to become an invasive weed.  For example, it can become invasive in Europe.  In its native range, it is eaten by many native insects, which help limit it from choking out other plants.  I find that this plant typically shows evidence of various insects munching on the leaves; see the photos below for yourself!

• Symphyotrichum cordifolium | Wikipedia - A brief, general article on this species.
• Symphyotrichum cordifolium | USDA Plants Profile - A detailed repository of information on this species.
• Heart-leaved aster | Eloise Butler Wildflower Gardens - A detailed page on this plant, with great photos.
• Blue Wood Aster (Symphyotrichum cordifolium) | Illinois Wildflowers - Although this source focuses on the plant's presence in Illinois, it is extremely thorough and deep, especially at exploring habitat, growing conditions, and faunal associations.