Asters in the fall garden

It’s easy to lose your enthusiasm for perennial gardening right about now. Many plants have ceased to bloom or have dried up from the summer heat. But if you plan accordingly, you can have more than mums blooming in your fall garden. There is a considerable number of other “late-bloomers” to choose from.

Coreopsis, salvia, dahlias and helianthus continue to bloom well into fall just as the caryopteris, Japanese anemone, sedum, ageratum, golden rod and sweet autumn clematis start to show their color. Couple all these perennials with asters and your garden will keep you entertained through October.

But the real showstopper in September and October is undoubtedly the aster. Native to the United States, the New York aster, aster novi-belgii, and the New England aster, a. novai-angliae, have over 1,000 known cultivars although you won’t find that many to choose from. The colors range from pink and purple to red and white with blossom diameters from 1 to 2 1/2 inches.

The New England aster, also known as the Michaelmas daisy, fits our traditional image of an aster, relegated to the back of the border because of its height, about 3 to 5 feet. The species bears a mass of purple flowers with bright yellow centers from September through October. There are cultivars in various shades of red and pink including “Harrington’s Pink” and “Alma Potschke” both of which begin to bloom a little ahead of schedule in mid-summer. These two cultivars also remain aster-enthusiast’s favorites. “Alma Potschke” has an erect, compact growth habit, reaching about 3 feet in height. It has double, vibrant pink blooms that stand out against its deeper green foliage of alternating, lanced-shapes leaves. In contrast, “Harrington’s Pink” has smaller, soft pink blooms and lighter colored foliage. There is only one true white cultivar of the New England aster, called “Herbstschnee”. Unlike the other “whites” this one does not turn a light mauve color as it matures.

The New York Aster is the most common aster grown and hybridized. You can find dwarf varieties well suited to mass plantings as well as cultivars that reach 4 feet in height. These prolific perennials are stout plants because of their woody stems. If they are taken care of properly, they are rarely in need of staking, although I recommend it in a formal perennial border. They prefer full sun in well-drained, rich soil. They will do best in moist soil but can tolerate drier conditions.

A staple in our fall garden is “Raydon’s Favorite” which is aromatic when it rains, like balsam or mesquite, and by October it opens to a mass of purple blooms. I get it to bloom later and stay a bit more compact by cutting it back by half in early summer.

In a more formal perennial border, asters should be divided every other year by removing the main plant and replanting the newer off-shoots. Biennial division allows for a healthier, compact plant with more blooms and a tidier appearance. Some cultivars reseed more prolifically than others so take care to deadhead late in the season to avoid seedlings. Seedlings revert to the wild state and will have violet flowers so you must take divisions or cuttings for accurate propagation of cultivated varieties.

In naturalized areas regular division is not as important because asters will perform well enough for your enjoyment and reseeding may not be an issue. Because asters are native to the southern United States, they are a perfect perennial to add to naturalized areas.