FORTE: Asters – stars of the October meadow

Theresa Forte

By Theresa Forte, special to Postmedia Network

Late-season asters provide an important food supply for bees and other pollinators. (Theresa M. Forte/Special to Postmedia Network)

Late-season asters provide an important food supply for bees and other pollinators. (Theresa M. Forte/Special to Postmedia Network)

Cool October days paint Niagara’s meadows and woodland edges with a palette of violet, blue and white asters, providing the perfect backdrop for the vibrant reds, oranges and yellows of our autumn trees.

Asters are native North American wildflowers and bloom with single, double and semi-double flowers in shades of white, pink, lavender, violet, blue and purple. They can vary greatly in height (20 centimetres up to 250 cm tall) and can self-seed like mad if you are not careful.

Do your homework and select well-behaved, disease resistant cultivars and you will enjoy their showy, late season colours for many years to come. Asters are attractive to bees and other pollinators.


Asters prefer a well-drained site that is evenly moist in the late summer and early fall. Most prefer a sunny location, although certain cultivars accept partial shade. The exception is the white wood aster (Aster divaricatus), which accepts full shade.

Asters are drought tolerant in the summer months, but need evenly moist soil in August and beyond, to produce a good show in the fall.

Pinching or shearing back the bloom tips in the late spring or early summer will encourage bushy plants with lots of flowers in the autumn. Tall varieties may need staking to stay upright once the flowers appear.


Asters are perennials that grow quickly. The clumps will spread and then weaken in the centre as they grow, expect to divide them every second or third year to keep them strong. To divide a clump of asters, dig them up and divide healthy chunks from the outside edges of the clump. Dividing the plants in the spring is the most reliable way to increase your stock.

Cuttings, taken in the spring before the hot weather arrives, can also be rooted for extra plants. Place cuttings in perlite/peat mixture and keep them moist until roots appear, usually within three to four weeks. Grow the rooted cuttings in a pot for the summer, transplant them into the garden in the fall. Remove flower buds until the plants are well established.


Sow aster seed directly in the garden in the early spring or late fall, In Perennials for Every Purpose, author Larry Hodgson recommends letting seed-grown asters bloom before selecting the healthiest and most attractive plants for your garden. Compost any plants that do not make this first cut. “Established asters self-sow freely, offspring are often less attractive than the originals,” Hodgson says. Deadhead plants by cutting off the top several inches of growth after they have finished flowering.


Powdery mildew can be a problem with many asters. Experts suggest leaving adequate space between plants, dividing them frequently and just watering the roots, keep the foliage dry if at all possible. The best defence is to look for disease resistant cultivars (check the tags) when selecting new plants.


White wood aster is native to North America and grows well in full shade. It forms a low mound of bright green leaves, bearing upright stems of small white, red-eyed daisies, held on black stems. This hardy plant will tolerate a sunny location, and naturalizes at the edge of a meadow, pretty ground cover in a woodland setting.

Heath aster (Aster ericoides) offers hundreds of tiny, star shaped flowers in shades of white, pink, blue and lavender above tiny, needle-like leaves, from mid-summer through to mid-fall. Position it toward the centre of a border, it will reach 75 to 120 cm tall and spreads up to 60 cm.

New England Aster (Aster novae angliae) blankets the countryside from Quebec to Alberta in shades of purple, blue and pink. In the wild, their size varies from a demure 30 cm to a mammoth 240 cm tall. Many beautiful cultivars are available through nurseries and garden centres, including the compact ‘Purple Dome’ (45 to 60 cm tall) with a tidy, dome-like form. New England asters enjoy full sun; good air circulation and spacing the plants will help prevent foliar diseases.

Michaelmas daisy, New York aster (Aster novi-belgii) have a more compact form and are more manageable in the garden than the New England asters. ‘Professor Anton Keppenberg’ offers bluish flowers on 30-cm-tall plants in late September; ‘Woods Purple’ and ‘Woods Pink’ are even shorter at 20 cm tall and blooms from early to late fall.

Aromatic aster (Aster oblongifolius) has aromatic foliage and is one of the latest asters to bloom, with blue-purple daisy-like flowers that persist well into late October. The plant can reach 60 to 90 cm tall; full sun and well-drained soils. Cut the plants back hard in the late spring.

Tatarian aster (Aster tataricus ‘Jindai’) features sturdy, tall stems topped with dense clusters of blue or purple flowers with showy yellow centres. These sun loving asters bloom late in the season, making them valuable additions to extend the seasonal colour in the garden. Give them plenty of space, they will reach 150 to 200 cm tall and spread 90 cm.

Asters are a beautiful, relatively self-sufficient plants that will add splashes of late season colour to your home garden. They are also fabulous cut flowers and are attractive to pollinators.

— Theresa Forte is a local garden writer, photographer and speaker. You can reach her by calling 905-351-7540 or by e-mail at