Zone: Typically 4 - 8, but variable
Soil: Variable - check label
Light: Full sun to part sun
Bloom colour: Pink, purple, blue, white
Bloom period: August into fall
Height: Typically 2 - 6 feet, but up to 8 ft.
Moisture: Typically medium, see note
Attracts: A variety of bees and butterflies.
Notes: Asters are simply a must in a wildflower garden because they flower in the latter part of summer and fall when there is a high demand for pollen and nectar. They act as host plants for Northern and Pearl Crescents. They also attract Monarch, Skippers, Painted Ladies and Sulphur butterflies. When goldenrods have finished, asters are still around to provide foraging bees with food.
Asters under modern plant classification systems are placed in several geni and if you go to a good nursery, then you should be able to find specimens that suit your particular soil and moisture requirements. For moist or clay soils, Aster puniceus is a tall and attractive specimen. However, what I consider to be the best looking Aster is also probably one of the most attractive for wildlife. New England Aster grows to around 6 ft and holds it own when naturalised with goldenrods. The best looking cultivar of this plant is the compact Purple Dome. Unfortunately, the semi-double flowers do not serve pollinators well.
Boltonia asteroides (false aster) can grow in a wide range of conditions including fairly dry soil. The species, growing to about 5 feet, is taller than the cultivars and may need support. The picture here shows a cultivar called snowbank. It is a dense plant covered with a spray of white flowers. It may still need support after heavy rains. Smooth Aster is more compact than New England Aster and it is excellent for attracting bees. While the individual flowers are not as pretty as the New England Aster, the sheer mass of flowers that it produces are impressive. It does well in dry sandy soils and is good for xeriscaping. Sky blue aster grows in similar conditions to smooth aster and only grows to about 30 inches high (75cm).
Asters provide some great flowers to brighten up the shade garden in the fall. Heart-leaved Aster (Aster cordifolius) matures into a plant with a decent spray of flowers that is attractive to bumblebees. It grows to about 30 inches high (75 cm). You might also consider Large-leaved Aster that does well in dry woods.
Here are some recommendations (many of those mentioned are now classified in the genus Symphyotrichum):
Full sun and medium moisture:
Aster novi-belgii, Aster novae-anglicae or the much taller Aster puniceus.
For clay soil, try New England Aster and Sky Blue Aster.
For sun and dry soil:
Aster laevis, Aster dumosus, Aster ericoides, and sky blue aster
For rock gardens, try Aster alpinus. It is rare wild plant in Ontario.
Aster cordifolius, Aster divaricatus and Aster macrophyllus.