The best plants for London gardens: colourful flowers to keep your outside space blooming until autumn

Gardeners and hair dye makers may not have much in common, but the quest for lasting colour unites them.

Plants that flower only briefly and then give up, exhausted, can’t earn their place when outdoor space is tight — we want troopers that pump out the blooms all summer long.

The staff of small neighbourhood nurseries are experts at helping clueless Londoners find their horticultural mojo.

So who better to ask for recommendations to fill window boxes, pots and borders with colour till autumn and beyond?

At Battersea Flower Station (batterseaflower station.co.uk), the friendly plant nursery wedged behind the railway tracks in SW11, John Schofield would go for nemesia for colour and scent all summer. “It’s great for pots, there are lots of colours and it flowers really late into autumn.”

He would add the perennial wallflower erysimum Bowles’s Mauve, with masses of purple flowers that bees adore.

But his number one for lasting colour in pots and window boxes are pelargoniums in pink, white or classic pillar box red. “In London they can flower right through the winter some years, especially if they’re on a sunny windowsill.”

Like most neighbourhood nursery people, Schofield is used to customers asking for advice. “Ninety per cent of our customers are beginners who worry that they’re bad gardeners, but I think good gardening is all about routine.

We think of London as a wet climate, but the city gets less rainfall than Rome. So get into the routine of watering, especially pots and window boxes in the rain shadow of the house.

And the key to really successful colourful planting? “Be bold. People often under-plant when they’re novices, leaving gaps and empty areas of soil. Aim for the pot or bed to look full when you’ve finished planting and it will look so much better.”

Peter Hulatt, MD at the biggest nursery in central London, Camden Garden Centre in NW1 (camdengardencentre.co.uk), would point long-lasting colour hunters in the direction of dahlias, lavender and patio roses.

He also rates Cape daisies (osteospermums) available in pink, orange, yellow or white; lobelia, cosmos and, if you want something really colourful, begonias — don’t worry, they’re considered fashionably kitsch these days.

Hulatt would add geranium Rozanne, with pink or white scabious to attract bees and butterflies. All will thrive in pots and window boxes as well as garden soil, but don’t forget to keep deadheading the old flowers to keep them blooming.

“Don’t just take the dead head off under the flower,” advises Hulatt, “snip the whole flowering shoot off where it meets the main stem.”

Pocket snips are so sharp and light to use they make the job almost pleasurable, especially with a glass in the other hand. Try Mini Snips, £5.99 (burgonandball.co.uk).

In south London, Peter Milne of The Nunhead Gardener (thenunheadgardener.com) recommends exotic-looking agapanthus, crocosmia and cannas for vibrant colour that lasts.

As for hanging baskets, stuff them with trailing petunias and bacopa for a summer riot.

In nearby Penge, Alexandra Nurseries (alexandranurseries.co.uk) is an oasis of plants, good advice, delicious cakes and vintage gardenalia.

The nursery’s Carolyn Harding would recommend salvias for long-lasting colour, from blues to purples and reds. The red-and-white bi-coloured Hot Lips is a particular favourite.

She’d add sedum Carl, a bushy variety that will flower for an age, with flower heads you can leave on over autumn. “They look lovely when they catch the dew.”

And don’t forget penstemons, she says, with spires of vivid flowers in shades from retina-burning pink to claret. She particularly loves the pearly pink variety Evelyn.

Pack some of these into pots or borders this weekend and, as long as you remember to water and deadhead them, they will provide heart-lifting bursts of colour all summer so you can concentrate on important things — like lighting the barbecue.