September Flowers for Stunning Late-Season Borders

September is when your flower beds give a last hurrah before settling down for the winter. Relax in your garden and enjoy the last of the summer sun surrounded by colourful borders or pots packed with dahlias, asters, rudbeckias and fuchsias.

September is one of my favourite months of the year. By the time it rolls around, I’m longing for cool, crisp mornings and colourful autumn leaves, while still wanting to garden in a t-shirt during the day. One of my not-so-guilty pleasures is sitting out with a cup of tea, watching the bees and butterflies flutter around the late-season blooms, and feeling a comforting sense of limbo before we move forward into autumn.

It’s also a time to prepare for next year’s flowers by planting bulbs, sowing seeds, taking cuttings and dividing perennials. Use our September gardening guide to make your own to-do list for your garden this month.

 

September flower of the month: Anemone 'Honorine Jobert'

Japanese anemones brighten up the garden when most flowers are starting to fade, stretching their saucer-shaped faces up to the autumn sun. They’re also one of the few late-season flowers that can tolerate shade. Anemone 'Honorine Jobert' is a taller variety, growing up to 1.5 m, with single white-petalled flowers and brilliant yellow stamens. I’m looking to plant some underneath a pair of birch trees where I hope they’ll enjoy the dappled shade and well-drained soil.

These pretty plants do have a tendency to wander at will, making them best suited to larger borders or woodland gardens where they have room to spread. In smaller gardens, you can grow them in containers or plant the anemone inside a ring of polythene inserted into the soil – this will help contain the rhizomes.

If you want to brighten up your garden, you can get 25% off Anemone 'Honorine Jobert' this September.

Plant it with…

Hosta 'T-Rex': Hostas are a perfect companion for Japanese anemones, and the huge green leaves of the ‘T-Rex’ provide a lush carpet for the pretty white flowers of ‘Honorine Jobert’.

Verbena bonariensis: The contrasting colour and texture of Verbena bonariensis make it the perfect colourful counterpart for ‘Honorine Jobert’ in a mixed herbaceous border.

Dryopteris 'Brilliance': This colour-changing evergreen fern is an excellent choice for ground cover in shady areas. It shoots out bright orange-red fronds in spring that mature to dark green leaves.

 

Aster 'Grape Crush'

Aster ‘Grape Crush’ is an eye-catching New England aster with dense clusters of dazzling purple flowers. Once fully grown, it forms a neat, round mound approximately 75 cm high. The plant’s green leaves hold their spot in the border until late summer, when an explosion of colour places this aster firmly as the star of the show. The flowers are a draw for bees and butterflies, as well as envious neighbours whose gardens are beginning to look a little drab.

Aster ‘Grape Crush’ is a low-maintenance, well-behaved plant. It won’t take over your border, and as long as you remember to water it occasionally during dry spells, it’ll give you (and the wildlife) plenty of flowers for months. It will benefit from being divided every few years. This aster’s shapely nature means it won’t look out of place in a formal garden, though it’s equally at home in a cottage garden or a sunny border.

Plant it with…

Calamagrostis 'Karl Foerster': This tall grass is a perfect backdrop for bright asters, with complementary colour and texture.

Kniphofia 'Mango Popsicle': Pump up the colour with Kniphofia’s fiery orange flowers – a dramatic contrast to the tight purple blooms of Aster ‘Grape Crush’.

Nepeta 'Purrsian Blue': This dwarf cultivar of catmint flowers from May through to September, adding interest to a border before the aster’s time to shine.

 

Dahlia 'Dalina Maxi Sonora'

Dahlias should still be going strong in September, and Dahlia ‘Dalina Maxi Sonora’ is a stunner for any sunny garden. It’s a compact variety that produces large, yellow pompom flowers from mid-summer through to the first frost. You can plant it in pots for a delightful addition to a patio garden or show it off in a small border where it won’t be overwhelmed by larger plants.

Like all dahlias, ‘Dalina Maxi Sonora’ likes a sunny, sheltered spot and regular watering and feeding. Keep picking or deadheading flowers to encourage new blooms – although they don’t have the longest stems, the flowers add a delightful sunny tone to a vase of flowers. To make sure you get the best show of flowers year after year, lift and store the tubers over winter or, if they’re in a container, move it to a frost-free greenhouse or shed.

Plant it with…

Marigold French 'Durango Mixed': Marigolds can help deter pests from your dahlias and attract early pollinators before your dahlias start flowering.

Cosmos sulphureus 'Brightness Mixed': This colourful mix of cosmos complements the dahlia’s yellow blooms, creating a warm-toned border that’s a magnet for insects.

Nasturtium 'Jewel Mixed': Nasturtiums are worth growing in their own right, with bright edible flowers, but they’re also a useful sacrificial crop, drawing aphids away from your dahlias.

 

Clematis 'Nelly Moser'

Clematis ‘Nelly Moser’ is a top choice for any garden with a bare patch of wall and a bit of shade. It blooms twice a year – once in late spring/early summer and again in early autumn – with each large flower having striking white petals slashed with pink, rather resembling a candy cane. The colour fades in strong sun, so choose a semi-shaded position – a north-facing wall is ideal.

It can take a couple of years for clematis to get going, but once they do, they’re relatively easy to look after. They’re hungry plants, so add plenty of organic matter when planting and feed during the flowering period with a high potash fertiliser.

Plant it with…

Rosa 'Snow Princess': Clematis and roses go together like jam and cream. This climbing rose tolerates partial shade and produces fragrant white flowers from June to September. 

Penstemon 'Apple Blossom': With similar candy-cane colouring, this hardy perennial would work well in front of ‘Nelly Moser’ in a mixed border.

Mixed lettuce: It may be controversial to throw edibles into the mix, but the shaded, moist soil around the base of a clematis is ideal for growing summer lettuces. Choose a mixed pack of seeds for varied colour and texture.

 

Rudbeckia 'Goldsturm'

This sunny coneflower gives a final blast of colour to your garden or to a vase of flowers, which is particularly welcome on grey September days. The golden petals surrounding the black, conical centre are a magnet for pollinators and a welcome addition to any wildlife garden. You can plant Rudbeckia 'Goldsturm' in large containers, but it’s best suited to garden borders and looks particularly spectacular if you have the room to plant it in large swathes alongside other flowering perennials or grasses.

Deadheading helps encourage the plant to keep flowering through to October, but it’s nice to leave the final seed heads on at the end of the season to provide winter food for birds.

Plant it with…

Salvia 'Pink Amistad': Create a vibrant mix of colours by planting Rudbeckia ‘Goldsturm’ alongside these tall spikes of bright pink flowers. They flower from June through to the end of October, adding long-lasting colour and scent to a border.

Monarda 'Cambridge Scarlet': This bright red bee balm flowers through to September and pairs well with Rudbeckia ‘Goldsturm’ in a hot border. 

Persicaria 'Alba Junior': Soften rudbeckia’s hard lines with the delicate white flowers and muted tones of Persicaria ‘Alba Junior’.  

 

FAQ

What flowers are in season in September?

There are plenty of flowers to brighten your garden in September, including asters, rudbeckias, dahlias, fascias, sedums and fuchsias. Japanese anemones such as Anemone 'Honorine Jobert' grow well in shaded borders, and Clematis 'Nelly Moser' is a good choice to add colour to a north-facing garden.

What flowers can I plant in September in the UK?

September is a good time to plant perennial flowers like heucheras, camellias, hostas, clematis and hardy geraniums. You’ll also want to get your spring and hardy summer bulbs in the ground. Daffodils, in particular, should be planted by the end of September. You can also plant biennials like honesty, Sweet William and foxgloves that were sown in the summer.

What is September’s birth flower?

Asters and morning glories are the birth flowers for the month of September. Asters are easy to grow and produce daisy-like flowers in a range of bright colours. Morning glories are fast-growing vines with flowers that bloom for a single day. They symbolise love, renewal and new beginnings.

Want to plant your own birth flowers for September? Sow Ipomoea 'Heavenly Blue' (morning glory) seeds in spring to get stunning sky-blue flowers from June all the way through to October. Aster ‘Grape Crush’ is a versatile perennial with masses of bright purple flowers.