How to grow hardy asters for dry gardens

Although North American asters (especially named forms of Aster novi-belgii)  tend to be thirsty plants prone to mildew, many asters bred from European species are tolerant of drier conditions. Aster amellus, sometimes known as the Italian aster, is perfect for the front of a border with large, well-rayed flowers that appear from August onwards. The two most worth growing are 'Veilchenkönigin'  (‘Violet Queen’ AGM), a deep-violet with dark middles and leafy stems which seems to flower on and on, due to being sterile, and 'Rosa Erfüllung' (‘Pink Zenith’). Both were bred by German nurseryman Karl Foerster in the 1950s and both will only reach under two feet (40 - 50 cm).  

The longest-flowering aster of all is A x frikartii ‘Monch’ (a cross between A. amellus and A. thomsonii) which often begins to open its large lavender daisies in July. It has deep-green, rough-to-the touch foliage and a slightly floppy habit, so is also best at the front despite reaching three feet (90 cm). ‘Monch’ is completely drought-tolerant and very hardy, although it dislikes wet soil in winter. Only divide asters, or Michaelmas daisies, in spring just as the growth breaks. Replant the pieces into the ground with a sprinkling of bonemeal.

How to grow

• Plant your drought-tolerant asters in a sunny position in well-drained soil. If in doubt add some grit to the soil underneath the plant to improve drainage.
• Always plant in spring, rather than autumn, if you can unless you have very well-drained soil. Keep new plants watered in dry seasons.
• Varieties of A. amellus will need dividing every fourth or fifth year to maintain vigour.
• Aster x frikartii can remain undivided for many years. However if you see die back in the middle of your clump, make a note to split up in the following spring.
• Cut down after flowering.

How to divide

• Lift the clump in spring as it begins to grow away. Either pull into hand-sized pieces, or use two back-to-back forks to split the clump.
• Discard the old woodier pieces.
• Replant smallish pieces into a fresh position - about a foot apart.
• Add grit to the base of the hole on heavy ground.
• Water until established.

What to plant with asters

Asters are good garden value because their attractive buds are a feature long before their flowers. Try to use them with spikes or saucer shapes, rather than with more daisies. 'Veilchenkönigin' ('Violet Queen') is very vibrant and will shine in front of the fluffy caterpillars of Pennisetum orientale, a grass that does well in warm situations. However the ponytail grass Stipa tenuissima, which is easy in all gardens, also frames this vibrant aster well.  'Veilchenkönigin' is also good against the spires of pale pink and blush-white penstemons such as 'Pearl' and 'Hidcote Pink'. Purple is also an excellent foil for lemon yellow and Achillea ‘Moonshine’ makes a perfect partner.

 

Varieties of drought-tolerant asters

Aster amellus

This wild aster was used medicinally as a decoction and a poultice by the Greeks and Romans for a variety of inflammatory ailments, which is possibly why it became rare in the wild. The species name is thought to have come from the River Mella, an Italian tributary of the River Po.

This aster, although rare in the wild, can still be found on free-draining ground on sunny limestone slopes through central France, northern Italy, the Czech Republic and the Caucasus. There are 30 named varieties of A. amellus.

A. amellus 'Veilchenkönigin'

The most sparkling and pristine of all, with vibrant purple straight-rayed daisies held on erect stems that reach just 15in high. It is also a butterfly magnet, perfect for the front of a sunny border, and will flower generously from late August and throughout September. Each flower has a thick layer of slender petals surrounding a tight golden eye reminding me of thickly-coated purple mascara on a young girl.

A. amellus ‘King George’

This was selected and raised by the British nurseryman Amos Perry in 1914 and it made Italian asters popular with gardeners within months. Apparently Perry intended to call his star plant 'Kaiser William' - until history intervened. It became 'King George' instead.  

All amellus varieties are drought-tolerant and perform in well-drained soil. This makes them useful in drier gardens where later-flowering North American asters either fail to thrive or develop mildew.

Aster x frikartii

This difficult cross was made by Swiss nurseryman Carl Ludwig Frikart (1879-1964) using A. amellus with A. thomsonii – the latter a Himalayan aster that’s now thought extinct.  He named eight seedlings after Swiss mountains and three, 'Eiger', 'Jungfrau' and 'Mönch',  are still with us.

A. x frikartii 'Mönch'

This sterile aster produces no seeds and this helps to make it the longest flowering aster of all. It reaches 3ft tall but is slightly lax, with dark green foliage that flatters the loosely rayed lavender-blue flowers.  Frikart also produced 'Wunder von Stäfa', but this seems to be the same plant as 'Mönch'.

'Flora's Delight'

Alan Bloom repeated the cross using A. thomsonii 'Nanus' and the Twenties variety A. amellus 'Sonia' to produce this long-flowering pink in 1964, naming after his second wife. It has greyer leaves and needs well-drained soil to avoid loss from winter wet.

Other drought-tolerant asters

A. turbinellus

This aster, from the dry prairies of the United States, has blue green leaves that clasp the stem and an umbrella of small lavender flowers that make it look like a heat haze when it flowers in August and September.

A. schreberi

A white-flowered aster that takes up room, producing white stars by August. Found on the edges of woods in North America, from New York to Michigan and Virginia, growing on dry, sandy soil and introduced to Britain in 1818. Schreber's aster (as it is also called) looks good close to dark-leaved shrubs such as Cotinus coggygria ‘Royal Purple, the smoke tree.  Not as pretty as A. divaricatus.

Aster laevis ‘Calliope’

Tall and upright, reaching at least four feet (120cm) this dark-stemmed aster with the dusky foliage bears lax heads of lavender flowers on leaning stems. Goes well with prairie planting. 

Aster ‘Vasterival’

Tall airy aster with lilac-pink flowers from late September onwards into autumn. Dark stems and narrow leaves. Le Vasterival is a botanic garden in France.

Supplier

Old Court Nurseries - www.autumnasters.co.uk

 

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