Symphyotrichum Species, Blue Wood Aster, Heartleaf Aster, Wild Aster

It makes a lovely mass of small aster or fleabane-like flowers of pale blue or white with a bluish tint. Very similar to the White Wood A...Read Morester, S. divaricatus, that is also nice. This species can grow in full sun, where it has more flowers in display and less leaf showing above. It should be able to grow in slightly alkaline soils too, not just acid ones.

Hardy at least to Z3.

This species can grow and flower fairly well in heavy shade and in difficult dry shade, and it can b...Read Moree a useful plant under those conditions---especially since it blooms in autumn. It also performs well in full sun, but there there are generally better perennials to grow.

I see some plants reach 5' tall, though they're more usually between 18" and 3'. The flowers are small (1/2") but profuse, and in flower this plant is fine-textured. The flowers are useful in cut flower arrangements.

It's native and commonly grows wild around here. A common weed of urban wasteland, especially in the shade of Ailanthus trees and Norway Maples, it self-sows here with enthusiasm. Seedlings generally require a trowel to remove unless the soil is very well prepared. I generally treat it as a weed, as do most gardeners around here.

Despite the common name, flowers are usually white with only a faint bluish tinge (really bluish violet rather than blue, but so faint it's hard to tell), the color of skim milk. I often see some variation in the amount of blue-violet tinting, but I've never seen any that could be described as "medium blue". I hope some enterprising plant breeder will develop a form with a more saturated blue-violet flower color. I occasionally see a pure white form, and I find it more desirable than the skim-milk color, especially since it stands out better in the shade.

Frequently confused with A. divaricatus, a similar native wood aster, but with pure white ray florets. Compared with A. divaricatus, A. cordifolius is slightly later blooming, taller, more upright, with flowers that are smaller individually but often more profusely borne. I find it more attractive. A. divaricatus spreads by runners, but A. cordifolius is a clump-former.

Tolerates clay soil and pH 5.7-7.5 http://www.genesisnurseryinc.com/Up Ur C/C14 asters sym-xan....

Aster 'Little Carlow' is usually listed as A. cordifolius, but it's a hybrid between A. cordifolius and A. novi-belgii.

11/21/2015: This perennial has been growing in my esteem, especially as it's one of the few that bloom well in shade in autumn.

I see a lot of genetic variability in this species, and see a lot of room for breeding and selection, for height, flower color, floriferousness, and bloom time. I have a tall pure white form, which appeared spontaneously in my yard. Another consistently blooms much later than the others, beginning a month later, in mid October, and still in full bloom on November 21.

Native to North America, plant this with spring blooming flowers to provide extended color and interest in the woodland garden well into ...Read Moreautumn. It creeps by rootstocks to form a nice patch. Prefers part shade but can grow in shade. Distinctive heart-shaped leaves.

This aster grows wild around my property and to be honest, its self-seeding is quite a nuisance. It also spreads by runners and doesn't s...Read Moreeem to be too fussy about the soil it weasels into. It prefers a little shade and the plants grow larger and more robust with adequate moisture. Hybrids on the market might be better behaved but this wild species should be confined to the wildflower garden.