September is a special transitional month, when we say goodbye to the long hot days of summer, but are not yet into autumn colours and leaf fall. It is a month tinged with the sadness of the loss of summer, as the light mellows and days cool, so we need to think carefully as designers how to ensure it is not empty with melancholy. September can present charms of its own, perhaps not as vibrant as mid summer, but subtle and beautifully coloured flowers and the shapes of seedheads and grasses really come into their own. Rosehips and blackberries offer colour and beauty as well as food for the birds. Apples and crab apples are starting to ripen and the berries on Pyracantha, Viburnum opulus (Guelder Rose) and Sorbus (Rowan) are coming on.
Flowers that come into their own in September include Hydrangeas, Sedums and Michaelmas Daisies (Asters). Dahlias and many Salvias are still vibrant and Cosmos, the little daisy-like flower Erigeron karvinskianus and even Nasturtiums will flower until the last frosts. Achillea, Echinops (Globe thistle), Eryngium (Sea Holly), Rudbeckia, Solidago (Golden Rod), Heleniums, Eupatorium purpureum (Joe Pye Weed), Kniphofia (red hot poker), Penstemon, Monarda and Echinacea still have colour and interest, and the seedheads of Dipsacus (teasels) provide architectural beauty.
Crocosmia puts on a welcome show of vibrant reds and yellows, and late flowering Clematis provides purples and mauves. Anemone x hybrida (Japanese Anemones) are a reliable source of colour for light shade. Nerines need a sunny sheltered spot and light sandy soil but are well worth growing for their bright pink blooms, if you have the conditions, and Colchicums come into flower at this time of year. Verbena bonariensis is very popular as it provides a ‘screen’ that can be seen through, though I find it isn’t hardy enough to be grown as a perennial in Oxfordshire and surrounding counties. Sometimes I use the wild flower Linaria purpurea (purple toadflax) as an alternative. Perovskia is also very striking at this time of year and its silver stems continue to provide interest through the winter. The feathery leaves of Foeniculum vulgare (fennel) provide an attractive accompaniment to autumn flowers. Sanguisorbia is also very attractive at this time of year, with its bottlebrush flower spikes, but most species require moist soil.
Amongst the grasses, Miscanthus is popular. Panicum virgatum ‘Rehbraun’ turns a lovely red then purple as autumn approaches. Molinia caerulea subsp. arundinacea ‘Transparent’ has purple seedheads maturing to gold, held above green stems which turn yellow in autumn. Other favourites include Stipa gigantea and Calamagrostis. Grasses really come into their own at this time of year and there are a great many to choose from, but most require an open sunny position and free draining soil. For more information on grasses read “Grasses” by Roger Grounds published by Quadrille Publishing Ltd in association with the RHS.
With so many plants to choose from there is really no excuse for not having interest in the garden in September. The job of the garden designer is to weave them together to create sublime beauty that helps us mourn the passing of summer and eases us into autumn.