September is an underrated month in the garden. While summer may be over and some flowers have faded, there are still plenty of ways to enjoy a colourful garden at home.
Growing long-flowering perennials is one of the best ways to extend the display. With the right varieties, you can enjoy vibrant blooms well into autumn, bringing colour and interest to your garden as the seasons change.
'September can be a surprisingly colourful month in the garden, and there are plenty of perennials that will continue flowering as we move into autumn,' says Angharad James, brand manager at Baby Bio®.
'The trick is choosing varieties with a naturally long flowering season, then giving them the right care to help them keep producing blooms for as long as possible.'
With this in mind, we asked experts to recommend the best long-flowering perennials to plant for a beautiful September garden.
1) Dahlias
'Dahlias are absolute stars of the late-summer garden and, with a little care, can continue flowering right through September and often until the first frosts,' notes Angharad. 'With so many different colours, shapes and sizes available, they’re also one of the easiest ways to inject plenty of colour into borders and containers at this time of year.
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'Keep deadheading regularly, cutting spent flowers back to a healthy pair of leaves rather than simply removing the flower head. Dahlias are hungry plants, so continuing to feed them with a high-potassium feed while they’re actively flowering can help support further blooms.'
2) Japanese anemones
'Japanese anemones are fantastic for late-season colour, often flowering from late summer right through September and into October. Their delicate pink or white flowers sit on tall stems above the foliage, so they bring height and movement to a border without feeling too heavy,' explains Sarah Rumbles, garden expert at Crane Garden Buildings.
'They’re particularly useful in areas with partial shade, so can work really well alongside a garden building, wall or mature planting where other flowering plants might struggle. Once established, they’re also relatively low maintenance, making them a great choice for gardeners who want reliable colour year after year.'
3) Penstemons
'Penstemons are fantastic value because their flowering season can stretch from early summer well into autumn. Their colourful, bell-shaped flowers bring plenty of interest to borders and are also popular with pollinators,' Angharad says.
'Regular deadheading will help prevent the plant putting its energy into producing seed and encourage it to keep flowering instead. Don’t be tempted to cut the whole plant back in autumn though, as leaving the top growth in place can offer some protection over winter.'
4) Rudbeckia
'Rudbeckias really come into their own towards the end of summer. Their rich yellow and golden flowers work beautifully with the softer light and changing colours of September, so rather than looking like a summer plant hanging on, they naturally help bridge the gap between summer and autumn,' Sarah explains.
'They’re also excellent for pollinators and their dark central seed heads can continue adding interest after the petals have faded, so there’s no need to be too quick to cut them back.'
5) Heleniums
'With their warm shades of yellow, orange and red, heleniums feel perfectly suited to September. They naturally begin flowering later in the season, so they can still look at their best just as many traditional summer favourites are starting to fade,' Angharad explains.
'Deadheading spent flowers can prolong the display, and taller varieties may benefit from some support, particularly as autumn brings windier weather.'
