Alpine Aster Facts

Characteristics

• The Alpine aster, sometimes called the rock aster, is a herbaceous perennial native to the mountains of Europe. The plant is about 1 foot tall and grows as a slowly spreading clump, with foliage that starts as gray-green in spring but deepens to dark green by summer. The plant has abundant blue-violet flowers with thin, raylike petals surrounding a bright yellow center. It usually blooms in May through June, producing a single flower at the end of each stem and can attract clouds of butterflies.

Location

• The Alpine aster does best in a spot that gets full sun for most of the day, although it benefits from some light afternoon shade in areas with hot summer sun. It can grow well in any type of climate within its range but prefers cool summers. The plant might slow its growth and die back in late summer in an area prone to hot, humid summer weather. Alpine aster also needs a spot with good air circulation, to help keep down fungal diseases that can become a problem in extra moist locations.

Soil and Water

• The Alpine aster grows in any type of moderately fertile garden soil that's well-drained. You can increase your soil's fertility by adding some compost at planting, but avoid adding fertilizer since this can promote leafy growth at the expense of flowering. The plant needs an average amount of moisture but isn't tolerant of standing water or soil that tends to stay soggy after a rain or watering. If your soil is rich in clay and holds water for long periods, add some sand at planting to increase its drainage.

Propagation

• Alpine aster spreads slowly, increasing the diameter of its clump over several years. You can propagate the plant by dividing the clump, using a knife or sharp spade to remove pieces from the outer portion of the clump. Fill in the resulting space around the mother plant with soil and plant the division in a new location. You can also take cuttings from an Alpine aster plant, choosing young stems and keeping them in wet sand or soil-less mix until roots develop, generally in two or three weeks.

Problems

• Alpine aster is prone to infestation by aphids or mites and to several fungal diseases, such as gray mold, rust and leaf spot. These diseases are best prevented by clearing debris from under plants regularly and watering plants with a soaker hose or drip irrigation to minimize wetting of foliage. When mites or aphids appear, spray the plant with insecticidal soap, diluted at a rate of 5 tablespoons per gallon, ensuring that foliage and stems are completely drenched in the solution.