Plant of the month - August

Aster divaricatus @ Rosemoor

A native of eastern North America, Aster divaricatus is a valuable, tough, summer to autumn-flowering perennial. Although of rather sprawling habit, it is a very effective informal ground cover for the border edge or in woodland. It can notionally grow to 60cm (24in) high and as much across, but typically the stems are almost prostrate, a striking dark purple in colour that sets off the mid-green foliage nicely.

From mid-summer onwards clouds of small white starry daisies are borne for a number of weeks, the whole effect being rather charming, especially if clothing a bank or cascading over a low wall.

Gertrude Jekyll recommended this plant highly as a subject to flop among the leaves of bergenias in the latter part of the season, as it is quite gentle and easy to control. Take her advice and don’t try to stake it, it somehow never looks at ease when growing upright.

At Rosemoor we grow this stalwart plant in the Formal Garden, the Stream Field, in the shady Gully and in Lady Anne’s Garden.

 

Aster

The asters comprise a genus of around 180 species of annuals, biennials, perennials and subshrubs. Asters are found in a variety of habitats ‑ in the northern hemisphere (particularly North America), these plants grow in habitats ranging from mountains to moist woodland areas while the relatively few shrubby species originate from South Africa.

Asters are members of the Asteraceae family characterised by their composite flower-heads, with the central disc composed of up to 300 individual flowers, usually yellow or orange. This is surrounded by large, white or brightly-coloured rays, designed to attract pollinating insects. The flowerheads are either solitary or borne in terminal corymbs, racemes or panicles on branching stems (erect or spreading).

The large number of aster species and cultivars means that the gardener can chose a plant for almost any situation including borders, wildflower gardens, streamsides and dry sites.

The name aster comes from the Greek word for star, in reference to the shape of the flowers. Many garden asters are also known as Michaelmas daisies.

 

Aster divaricatus

Aster divaricatus (a native of eastern North America) is a clump-forming perennial with arching, wiry, black-purple stems bearing loose corymbs of white flowerheads with brownish-yellow disc-florets from midsummer to mid-autumn. The name divaricatus means spreading and refers to the plant’s straggly growth.

 

Cultivation

• Grow in partial shade in a moist, moderately fertile soil. Mulch after cutting back in late autumn.

• Generally trouble-free, however, may be vulnerable to aphids, slugs, snails, leaf spot and grey mould.

 

Propagation

• Sow seed in containers in spring or autumn in a cold frame.

• Propagate by division in spring.

 

Links

• Dividing perennials