Some plants look best when bathed in the golden syrup of autumn sun, writes Jane Powers
I'm not quite sure how I feel about this month. The increasingly darker evenings and murkier mornings make it seem as if the days have sprung a leak, and are being drained of their vigour. This gradual depletion of light leaves me a little despondent. On the other hand, the autumnal chill is heady and bracing, and the light - although there is a lot less of it - is high-calibre stuff: golden, warm and evocative.
In the garden, plants are lit up with an incandescent glow. Disparate flower colours find a common note under the amber filter of autumn, and become friends for the season. The screaming yellow rudbeckias and hectic crimson sedums that would clash viciously in the bright light of the midsummer border are suddenly the best of companions when bathed in the golden syrup of the autumn sun.
The daisy family, Asteraceae, reigns supreme in the late-summer and autumn garden. You could have a vibrant, long-lasting border with nothing other than members of this large clan. Among them are the brassy and coppery daisies that we associate with August, September and October: the sunflowers (Helianthus), annual and perennial; Helenium; Heliopsis; and the many rudbeckias. If you can guide them successfully through infancy (when they are popular with slugs and snails) they are mostly trouble-free plants - although none likes a very dry, light soil.
Directly opposite these flaming sizzlers on the colour wheel are the Michaelmas daisies, or perennial asters, with their cool blues and mauves. The novi-belgii kinds (New York asters) are more prone than others to mildew, and unless you are a fan of fungicidal spray, they are best avoided. Cultivars of Aster novae-angliae (New England asters) and A. amellus are less likely to fall foul of the fungus, as is the lovely lavender-blue, yellow-eyed A. x frikartii 'Mönch'. The latter is sturdier than some, and is one of the earliest to flower: it is in full flight from August to October, and often into November.
Among the more showy of the late-blooming Asteraceae are the chrysanthemums. Most are too stiff and unsociable for a border, but a few - 'Mary Stoker' and 'Clara Curtis', for instance - arecongenial to the company of other plants. Situate them among lots of calming green foliage, or go the whole hog, and let them fight it out with equally brazen canna lilies or dahlias.
Ten years ago one of the only dahlias that was let into fashion-conscious gardens was the blood-red, dark-foliaged 'Bishop of Llandaff' (raised in Cardiff in the 1920s by Fred Treseder). But now that the colour temperature of horticulture has risen - with brighter, more tonally-saturated flowers becoming the norm - dahlias are being splashed around all the "best" borders. The Welsh plant, once known simply as "the bishop", now has to compete with five other dusky-leaved ecclesiastics, introduced last year: 'Bishop of Canterbury' (deep pink single flowers), 'Bishop of York' (yellow single), 'Bishop of Lancaster' (red double), 'Bishop of Auckland' (dark red single) and 'Bishop of Oxford' (orange double).
The new bishops probably won't be widely available for a year or two, but in the meantime, there is a host of other jewel-coloured dahlias that can add a rich glow to a late garden, including 'Arabian Night' (wine) 'David Howard' (orangey-apricot), 'Nuit d'Eté' (deep red) and 'Roxy' (magenta).
Staying within the Asteraceae family, there are two more members that are valuable late bloomers. Neither, however, has the characteristic daisy flowers of its kindred, so it may come as a surprise that they are related. First up are the goldenrods (Solidago), not recommended for hay-fever sufferers, but one of the few late-performing species with flowers that make good vertical accents. Then we have Eupatorium, including the tall and splendid American Joe Pye weed (E. purpureum) and our native hemp agrimony (E. cannabinum). The latter is a prolific self-seeder, so be prepared to do a cull of its hundreds of offspring in springtime.
Almost all members of the vast Asteraceae family (although not the highly-bred chrysanthemums and dahlias) are excellent bee and butterfly plants and for this reason alone, they should be well-represented in the September garden.
Another genus of late-flowering insect pleasers is Sedum, the stonecrops. The most often planted is 'Herbstfreude', more commonly (but incorrectly) known as 'Autumn Joy'. This fleshy-leafed plant has good, long-standing, pink plates of flower, which gradually fade to brick-red and dark rust as winter advances. Alas, while bees are keen on it, butterflies are not, preferring instead S. spectabile and its cultivars ('Brilliant' is probably the most readily available). New sedums are being bred all the time, with bigger and frothier flowers and more interestingly toned foliage. Of the dark-leaved ones, 'Purple Emperor' (about 40cm tall, with red flowers) is perhaps the best of the upright kinds, while 'Bertram Anderson' is a lovely, swarthy sprawler with cherry-coloured blooms. Sedums, being succulents, are happy in a sunny spot in the garden. They don't mind a dry soil, as long as you add some organic matter at planting time.
Plants that will flower just about anywhere - so don't give them your best position - are the Japanese anemones. They start to bloom in late July, and may go on until November. Grow them in awkward, shady places - behind gates or in a north-facing border - and let them light up the gloom with their pink and white heads carried on tall wiry stems.
Let's not forget the space on the floor of the garden, where late-flowering low-growers - mostly bulbous plants, including corms and rhizomes - can be accommodated. Among these are white and mauve Cyclamen hederifolium; purplish Crocus speciosus, C. sativa and Colchicum autumnale; and yellow Sternbergia lutea. Slightly taller are the lacy, white garlic chives (Allium tuberosum) and the pink, white and crimson-flowered Schizostylis coccinea.
With all these sterling plants shining in the golden light of autumn, I think I should come off the fence and declare a whole-hearted "yes!" for September. This is a good month in the garden.
DIARY DATE Thurs, 8pm at the National Botanic Gardens, Glasnevin, Dublin: illustrated talk by Royal Horticultural Society librarian Brent Elliot, The Family Jewels: Lindley Library of the RHS. Admission free.