Late summer perennials to keep your garden flowering for longer

It’s a bright September morning, cool but with the promise of a warm day as the sun rises over the trees in the east in my Hampshire garden. A perfect late summer morning that makes me glad to be alive…not least because our two nippers are back at school and nursery after 5 months of COVID lockdown, and I can finally get a proper day’s work done without interruption!

I take 5 minutes to enjoy the peace in the garden before starting work – and it is still bursting with life and colour, (and will hopefully continue to do so for another month or so, and in the case of some plants – until the first frosts).

A common theme when I am talking to potential clients is that they say that come August there isn’t much going on in their garden and they have resigned themselves to the fact that the show is over until the following May.

This always astounds me as there are so many wonderful plants out there that have a long flowering season or that are only just showing their true colours at this time of year. With a little planning you can have something in flower every single month of the year, even through the depths of winter. For late summer perennials there is so much on offer for you to consider, such as Anemones, Asters (or Symphyotichum as some of them are now named), Hylotelephiums, Salvias, Heleniums, Crocosmia and grasses such as Pennisetum. Mix them in with early flowerers so that when one plant goes over you have another species or variety ready to flower next it, with no gaps in service. And if you keep deadheading plants like Penstemon, Salvias and Cosmos you’ll get more flowers appearing in quick succession.

In my garden the perennial sage - Salvia ‘Amistad' - with its spiky deep purple flowers (loved by bees) grows alongside a pink annual Cosmos that I grew from seed.

Penstemon ‘Raven’, with its bell-shaped flowers mingles perfectly with the switch grass Panicum virgatum 'Rehbraun' whose leaves are just beginning to turn a reddish purple. (I must admit this planting partnership was a happy coincidence but I’ll chalk it up as a win). The silver leaves of the semi-evergreen Artemisia ‘Powis Castle’ makes a superb foil for the purple flowers of the Penstemon.

Astrantia major ‘Star of Billion’ is onto its second flush of flowers after I cut the faded flowerheads back earlier in the season. An extremely floriferous plant (hence the name) whose dome-shaped flowerheads remind me of a pincushion. The Astrantia is set off perfectly by the almost black foliage of the outstanding black elder – Sambucus nigra ‘Black Lace’.

The compact Crocosmia x crcosmiiflora ‘Emily McKenzie’ with its bright orange flowers gives a great pop of colour in a semi-shaded area of the garden.

Symphyotrichum (née Aster) ‘Little Carlow’ and Rudbeckia fulgida var. deamii make perfect late-summer perennial planting partners (try say that ten times as fast as you can after 2 glasses of wine), not least because the colours are from opposite sides of the colour wheel creating a complementary colour scheme.

The deep purple flower spikes of Agastache ‘Black adder’ backlit here by the early morning sun, are an irresistible magnet to bumble bees, and will flower through to October. They add height to the border and the vertical form contrasts nicely with flatter flowerheads like Hylotelephium (sedums)

The aptly named Oenothera lindheimeri ‘Whirling Butterflies’ is a wonderful airy plant with masses of white flowers which will keep going well into late autumn. A perfect choice for cottage gardens or prairie planting schemes. Seen here with the silver-leaved Artemisia ludoviciana ‘Valerie Finnis’ in the background.

Verbena bonariensis is an absolute classic for any sunny well-drained border with its vivid lilac-purple flowers heads. And given it’s see-thru form, it doesn’t have to be reserved for the back of the border. In my garden it contrasts nicely with the pastel yellow of the annual tobacco plant – Nicotiana langsdorfii (grown from seed from a freebie packet that came with my Gardens Illustrated magazine). Both the verbena and the nicotiana complement the lighter violet-blue flower spikes of the Russian sage – Persovskia ‘Little Spire’ in the background.

The garden designers favourite - Hydrangea aborescens 'Annabelle - packs a real punch with its large white flowerheads, and still looking fresh in September.

Another favourite for bees and butterflies - Echinacea purpurea with its purple daisy-like petals and bright orange cone seed-heads.

For more ideas on great late summer perennials head on over to the very useful RHS plant finder. Also your local garden centre could well have some great end of season bargains to be had. Until next time, happy gardening!