Blue Wood Aster or Heartleaf Aster

by cazort

The blue wood aster, Symphyotrichum cordifolium, a wildflower native to eastern North America: growing info and uses for this plant in gardening and landscaping.

The blue wood aster, Symphyotrichum cordifolium, also called the heartleaf aster or common blue wood aster, is a blue fall-flowering perennial wildflower native to eastern North America.

It is an unusually durable plant, adapted both to partial shade and urban conditions.

It is especially valuable as a late-blooming wildflower providing a blue color at a time when few other flowers bloom in such vibrant color. It is also a prolific bloomer, producing dozens of small flowers which persist for many days.

Blue Wood Aster in Bloom
Blue Wood Aster in Bloom
Photo by Alex Zorach

Quick Summary of This Plant's Attributes

  • 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.

Growing Conditions: This Plant is Adaptable

Sun to moderate shade, not heavy shade. Dry to moderately wet, but not very wet.

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, 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.

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

Growth Habit and Bloom Pattern

Sometimes upright but sometimes falling over, leading to a sprawling habit

The blue wood aster can grow upright, but its stems frequently fall over, leading to a sprawling habit.  It often sprawl 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.

Blue Wood Aster Blooming in an Urban Flower Bed
Blue Wood Aster Blooming in an Urban ...
Blue Wood Aster in a Semi-Wild Meadow
Blue Wood Aster in a Semi-Wild Meadow

Wind-dispersed Seeds

This plant is easy to grow from seed, and spreads readily.

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!

References and Further Info

Read and learn more about this species of aster

Closeup of Leaf, Flowers in Background

Note the heart-shaped leaf, explaining the name "Heart-leafed aster". Note also the insect damage to the leaf; insects frequently feed on, but rarely kill this plant.
Photo by Nadiatalent, Licensed under CC BY-SA 3.0
Photo by Nadiatalent, Licensed under CC BY-SA 3.0
I recommend this book if you live in the Southeast or Mid-Atlantic and are interested in learning more about growing and propagating wildflowers.
Growing and Propagating Wild Flowers

This book, the most complete and expert treatment of wild flower propagation and cultivation to date, offers a sure approach to gardening with native plants while practicing goo...

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Updated: on 09/27/2014, cazort
 
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Mira on 06/10/2014

:-) Yes, that's quite something, when a plant blooms so nicely, for so long, with so many flowers, in the shade.

cazort on 06/09/2014

Thanks! I think the combination of the color and bloom dates are one thing that makes this particular plant so appealing to me. It's relatively easy to find late-blooming plants that bloom white, but there aren't many other plants that bloom this color any time of year, especially in late fall.

I also was astounded at how many blooms the plant produced, and how long they lasted--weeks.

A few blocks over, I saw someone who had also planted this plant on a north-facing exposure with no direct sun (the plant pictured here has a south-facing exposure shaded by a large tree), and that plant also bloomed well even without any direct sunlight. I think that may have been when I decided I really loved this plant.

Mira on 06/09/2014

I enlarged your photos and these blue asters look quite nice. I love their color, that pale lila. And if it blooms late, when other flowers are already gone, well, that's wonderful :-)



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