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 1 - 6 feet, but up to 8 ft.

Moisture: Varies, see notes

Attracts: A variety of bees and butterflies.

Notes: Asters are beautiful plants with a bountiful supply of flowers while in bloom. They 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 as well as over one hundred other species of insects. They also attract monarchs, skippers, painted ladies and sulphur butterflies. When goldenrods have finished, asters are still around to provide foraging bumblebees with food. Asters reseed easily and start popping up all over the garden, but they are still easy to control. A few asters will also spread by rhizomes or stolons and some of these should be avoided in small gardens. Asters are really easy to grow from seed, so collecting a small amount from local sources is recommended.

Asters under modern plant classification systems are placed in several genera and if you go to a good nursery, then you should be able to find specimens that suit your particular soil and moisture requirements. Nearly all asters can grow in clay soils, and many of them can handle sandy soil as well.

Top aster recommendations for sunshine.

For moist or clay soils, Symphyotrichum puniceum is a tall and attractive specimen. Compared to other asters its size, large flowers and heavy bloom with its purple stems set it apart as a garden worthy plant. In the wild, I have mostly seen it in more northerly areas and at higher elevations such as the Laurentides where the soil remains cooler and moister. It will grow well in gardens, but it really does need constant moisture and plenty of sun to be at its best. It will bloom earlier than most other asters. In nature, its height is variable, but in more consistent garden conditions you should expect the plant to be between 5 to 6 feet high.

At lower elevations, New England aster is one of the best-looking species as well as being one of the most attractive for wildlife. It often produces deep purple flowers that are absolutely gorgeous. New England aster grows to around 6 ft and holds it own when naturalised with goldenrods. When this plant is in full bloom, it is top heavy with flowers and is going to need some support. This plant has a long bloom period and will continue to provide nectar to bumblebees and sweat bees well into October in Ontario. Cutting the plant down by half at the end of June will stunt the growth of the plant and prevent it from becoming lanky while enabling the plant to stay upright on its own. This is well before the blooming period and will not affect flowering. Unfortunately, many of the cultivars are semi-double flowers that do not serve pollinators well and so the straight species is recommended. If you do the "Chelsea chop" on the on the straight species at the end of spring, then you will have great looking plant with a large number of pollinators. New England aster can grow in sandy soil as well, but it will need watering to prevent the leaves from dying back before flowering.

Smooth aster, at 4 ft (120 cm), is more compact than New England aster and it is excellent for attracting bees. In drier areas with sandy soil, it would be a more suitable alternative to New England aster because the foliage will remain in good condition. It is an impressive plant with thick leaves that hug the stem and large blue flowers. I use tomato cages to support these plants in part sun, but it really does do well if given full sun. For raised beds in school wildlife gardens , this really is an excellent choice because you will not need to water it over the summer.

Sky blue aster grows in similar conditions to smooth aster and only grows to about 30 inches high (75cm). It does not require support as most of the vegetation is made up of basal leaves. The stems have much smaller leaves with a large number of flowers. The bloom is more airy than smooth aster. These characteristics make this plant a worthy addition to the garden.

There are several tall white asters that grow in the region, but they are often too aggressive for smaller gardens as they spread by rhizomes as well as seed. Avoid planting S. lanceolatum, S. pilosum and S. ontarioensis in particular.

A white aster to consider for drier soils that is native to Ontario is arrowleaf aster, Symphyotrichum urophyllum. It prefers part sun and can grow in a range of soils. The bloom is more upright than other white asters which gives it a nice form. It grows to about 3 feet high and will flower in late summer. It does not spread too much by rhizomes but it will reseed itself like most other asters.

The flat-topped white aster is another species to consider for moist soil. While it is not as attractive as New England aster, flat topped white aster is an excellent plant to attract wildlife. It flowers much earlier than other asters when a greater diversity of pollinators are around to take advantage. The nectaries are easily accessible so many beneficial wasps as well as bees will feed on this plant. It can be commonly found in drier areas along the coast or at higher elevations where the soil is cooler.

Boltonia asteroides (false aster) can grow in a wide range of conditions but it does prefer moist conditions. 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. This plant is not native to Ontario or Quebec, but it is found in most of Eastern North America

If you have lots of room, then Heath aster is another species that does well in dry sandy soil and is covered with such an abundance of small white flowers that the stems are difficult to discern. It is also only about 30 inches (75 cm) high and does not need support. While New England and smooth asters are frequented by bumblebees, hover flies and sweat bees, heath aster attracts beneficial wasps. Heath aster frequently hybridises with New England aster to produce white or lilac flowers. It reproduces quite easily and in wild areas, it may be the dominant plant. It is not really recommended for small gardens as it spreads quite quickly through rhizomes.

A shorter aster that does well in dry soil and part sun is calico aster. It is less than 2 feet high and is notable for the disc flowers that start off as yellow and turn to purple over time. While the individual flowers are interesting, the overall appearance is a bit weedy and it does not look great en masse. It branches out nearly horizontally and its form is a great clue for identifying it in the wild. It would be better to let this plant grow in between other plants. It will reseed itself generously. It is fairly easy to identify from other asters before blooming so it can be pulled wherever it is not wanted.

Top aster recommendations for shade.

Asters provide some great flowers to brighten up the shade garden in the fall. Heart-leaved aster (Symphyotrichum cordifolius) matures into a plant with a decent spray of flowers that is more attractive to bumblebees than any other shade plant that I have grown. It grows up to 3 feet high but typically has much less stature. The individual flowers are stunning. The plant has light blue ray flowers. The disc flowers in the centre start off at yellow and turn to a deep purple shade as the flower matures. Heart-leaved aster does spread by short rhizomes and by reseeding. Pull it as soon as you see it in areas where it is not wanted and you will find it easy to control. A much rarer shade plant of similar size is Short's Aster which has flowers that are nearly twice the size of heart-leaved aster. Combine it with zig-zag goldenrod or blue-stemmed goldenrod. It grows to about 30 inches high (75 cm).

You might also consider Large-leaved Aster and white wood aster, which both tolerate shady woods with the former plant doing well in more mesic conditions. These asters are smaller in stature and should be planted in front of other shade plants. Large leaved aster flowers earlier than other asters and has a long blooming season. White wood aster is the plant to choose for dry shade. It forms a compact flat spray of flowers. It will not stand out if you just plant a few, but it will look absolutely fantastic if you plant it en masse. The bloom is so dense that it is hard to see the foliage underneath. White wood aster combines well with Virginia blue bells, which dies back in early summer. This aster will fill in the spot and give a second round of blooming

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-angliae, Doellingeria umbellata or the much taller Symphyotrichum puniceum.

For sun and dry soil:

Symphyotrichum laeve, Symphyotrichum dumosus, Symphyotrichum ericoides, Symphyotrichum urophyllum and Symphyotrichum oolentangiensis.

For rock gardens, try Symphyotrichum alpinus. It is rare wild plant in Ontario.

For shade:

Symphyotrichum shortii, Symphyotrichum cordifolius, Eurybia divaricatus and Eurybia macrophyllus.