As days begin to shorten, we start to think of berries and autumn foliage colour – but this is also the season when an unexpectedly wide range of autumn-flowering hardy perennials start to come into their own.
Michaelmas daisies, now classed botanically as Symphyotrichum, are perhaps the first to come to mind, in their vast array of flower colours and flower forms and heights. Penstemons, too, can be kept flowering into November with regular deadheading.
But there are many other easy-to-grow perennials that light up the autumn months. This choice of 10 are all winners of the Award of Garden Merit (AGM) - an independent assurance that the varieties are reliable, good for normal garden use and widely available.
Numbers at the end of each entry refer to plant height and RHS hardiness rating.
Fragrance and flowers
Since agastaches began to come to the fore, we’ve started to depend on their aromatic foliage, their long season of flowers, and their appeal to butterflies. Agastache ‘Blue Fortune’ is one of the finest, with peppermint-scented foliage and upright spikes of violet-blue flowers opening in tiers from darker bracts. I can see a butterfly on mine as I write. This is a plant that demands good drainage and sunshine – as part of a Mediterranean scheme it’s ideal. And it will flower until October and never self sow. 1m. H6.
Classic Japanese anemone
The swaying white flowers of Anemone × hybrida 'Honorine Jobert' start to enliven our borders in August and those golden-centred slightly frilly saucers keep coming into October. Plant them in sun or partial shade: ideally with brooding shade behind them to highlight those gleaming blooms. Just one thing: allow 'Honorine Jobert' room to spread as the woody roots tend to extend – and if you move your plant, prepare for new shoots to arise at the old site. 1.2m. H7.
The perfect perennial?
Aster × frikartii ‘Mönch’ is one of the finest of all sun-loving perennials: neat and well branched but elegant, prolific, long-flowering and with soft lavender-blue petals surrounding a yellow eye. Lovely with grasses, sedums and schizostylis, it’s also good for cutting. Oh, and it's resistant to mildew and the flower colour varies slightly in different growing conditions. 90cm. H7.
From Japan in a matchbox
Chrysanthemums are always associated with autumn and even hardy types come in a vast variety of colours and forms. Chrysanthemum 'Mei-kyo' is one of the prettiest and most manageable. Making a neat, twiggy plant with unusually small foliage, for a couple of autumn months it produces small, button-like pompom flowers in pale purplish pink. The original cuttings of this variety arrived from Japan in a matchbox in the 1950s. 60cm. H4.
Red and blue combo
The bushy, slightly twiggy growth of the hardy plumbago, Ceratostigma plumbaginoides, brings us a rare combination of foliage and flower colours. The clusters of sharp blue flowers, a little like those of a periwinkle, open in September and October on wiry reddish stems, but the special feature of this indispensible plant is that the leaves start to turn scarlet as the flowers are at their peak. An essential front-of-the-border plant for sun. 45cm. H5.
South American sea holly
Now this is a dramatic plant. Eryngium pandanifolium is a monster relative of our native sea holly we find on gravel beaches, and whose habitat reminds us that good drainage is valued by this more imposing relation. First making a bold clump of narrow, softly spiny, slightly bluish leaves, from the centre erupt tall, repeatedly branching upright stems carrying small, tight, egg-shaped reddish-purple flower heads. 2.5m. H4.
We usually think of buying ginger in the supermarket rather than growing it in the garden, but this autumn-flowering ornamental ginger is so good it has received the Award of Garden Merit. Hedychium 'Tara' is an imposing plant with slightly leathery lance-shaped foliage and impressive heads of fragrant reddish-orange flowers. Best with good drainage and high fertility, it needs protection over winter in cooler areas. Good for dramatic effect. 2m. H4.
New slant on old favourite
And another new name, Hylotelephium is the new moniker for the hardy perennial sedums. Hylotelephium 'Red Cauli' gets its name from the rich crimson-red colouring of its gently domed flower heads, which are said to look a little like red cauliflowers – more like red sprouting broccoli, I’d say. Set above rich green, succulent foliage I’ve found that ‘Red Cauli’ makes a perfect partner for Aster × frikartii ‘Monch’ over many many weeks. 70cm. H7.
Long season lifeline
Salvia 'Amistad' is a plant that will grace your border from May until October, especially if deadheaded, so it does the job of two or three other plants. The shimmering purple flowers stand out to face the light from the near-black calyces, all held on long, slender, elegant and equally dark stems. I’ve used these in a vase with the last of the pink ‘Mary Rose’ roses. Lovely. 1.2m. H3 (needs winter protection in cold areas).
The recent Wisley trial of hardy autumn-flowering perennial saxifrages revealed to many gardeners the value of these neat little perennials. Saxifraga 'Shiranami' was one of the highlights, its double, clear white, starry flowers held over glossy, fresh green foliage for many weeks in autumn. Best planted in partial shade in that elusive combination of humus-rich but well drained soil. 25cm. H4.
Find out more about the Award of Garden Merit (AGM)
See Graham Rice's New plants blog
Alpines for autumn colour