Harbingers of Fall - Part III - Asters, Part 1, Etc.

Starting to bloom about the same time as eupatorium and liriope, begonia grandis (hardy begonia) also tells me the season is getting on. I talked about the hardy begonia in my article More Self-Seeders Covering Ground For "The Wilderness". Mine are in their glory now. One thing I forgot to mention was what a nice front of the border plant they are. Their large leaves overlap in an orderly fashion, bending gracefully to the ground and making a neat edge.

Just coming on now are plants that really wrap up the gardening season in my USDA zone 7 garden.

Asters

Of the 250 to 500 species of mostly herbaceous plants belonging to this tribe of the Compositae family, I only grow a very few, primarily because of lack of appropriate space for them. Asters are an important group, most providing flowers late in the season when most other perennials have given up. Aster means "star" in Greek, in reference to the radiating petals in the flower heads.

Asters, sometimes called Michaelmas daisies, are native to North and South America, Europe, Asia and Africa. The flower heads are generally made up of a yellow (although it can be purplish) disc flower surrounded by ray flowers in white, pink, red, purple or blue. Only clear yellow and orange are absent from the color range. There is a related plant, Linosyris vulgaris (European Goldilocks), sometimes, incorrectly, referred to as Aster linosyris or yellow Michaelmas daisy, that has heads of small yellow flowers. Also with yellow flowers and sometimes mistakenly classed as an aster, x Solidaster luteus is actually a hybrid between goldenrod (Solidago) and aster species. It is used extensively in the cut flower trade as a filler in bouquets, lasting in water for just over a week.

Asters range from small plants, suitable for the rock garden or front of the border, to giants six feet (2 m) tall or more, for the back of the border. They can be fibrous-rooted (clump formers) or rhizomatous (spreaders). Although most of them are pretty easy to grow, accepting most well-drained soils in sun or light shade, they will be at their best if given good, fertile soil. Avoid over-feeding of the garden hybrids, which will result in lush growth more susceptible to powdery mildew.

With some exceptions, they prefer fairly dry soil, but overly dry conditions and poor air circulation can contribute to the onset of powdery mildew. The hybrids are more susceptible to this disease than the species. To avoid mildew, give them room so that air can circulate; divide the hybrids at least every two years, before growth reaches six inches (15 cm) high, retaining only the healthy outer divisions, and water the soil, not the leaves, when there is no regular rainfall. The species also come readily from seed. In very hot climates, the garden hybrids do better with some shade from scorching sun.

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