Sarah Raven: The flowers I have that are flourishing superbly, despite the battering heat

As late-summer and autumn border fillers, long-lasting cut flowers and container troopers, rudbeckias are stellar — even in all this summer’s heat. The bright golden ones are not my cup of tea, but I adore the aubergines, mahoganies, crimsons and yellow greens. ‘Cherry Brandy’ is a long-standing stalwart I’ve picked until Christmas for many years and I love the seed-grown, ever-flowering mix ‘Sahara’, but they’re only a fraction of what is available with recent breeding.

We have 10 new varieties on trial in the garden here now, all doing superbly, despite the heat. Recently I went to the open days at Ball Colegrave in Oxfordshire, one of the biggest suppliers of bedding annuals and perennials to nurseries and garden centres around the UK. They had lots of new ones, too, including a crimson-centred, gingernut-petalled Sunburst ‘Radiant’ and a mix of more faded tones in ‘Rudy Double Rose Yellow’. Both really did look radiant and will surely be in lots of garden centres and nurseries very soon.

Next come the thunbergias, the good old black-eyed Susans, which have also had a major makeover, leaving primary yellow and orange behind in favour of more subtle, sultry beauty. Derry Watkins (of Special Plants Nursery near Bath) introduced me to ‘African Sunset’ in Autumn 2007 and I’ve grown and loved it ever since. A drought-tolerant, South African plant, this whole family looks like the kind of thing we all want. New and glorious hybrids of thunbergia keep appearing and every one is lovely in my view.

We grow them here up and over silver-birch teepees and hazel arches, sometimes on their own or mixed with other tender perennial climbers, such as rhodochiton, cobaea and Ipomoea lobata (syn. Mina lobata), reliably glorious almost to the end of the year.

Ball Colegrave had some inspiring combinations with a range of new thunbergias mixed with climbing sweet potatoes, with ebony or acid-green heart-shaped leaves. I loved pretty, soft Thunbergia ‘SunEyes Pink Beauty’ clambering up a frame with the elegant leaves of Ipomoea ‘Solar Power Black’ and the spectacular contrast of these same black leaves with the tangerine T. ‘SunEyes Orange Beauty’. Almost whatever heat and drought is thrown at these plants, they seem to thrive.

My next heatwave rave is the combination of a top-notch nemesia paired with a compact salvia with perhaps one of the trailing sweet potatoes added in. Nemesias, like thunbergias, come from South Africa and they’ll take almost any amount of heat and drought. Now available in some great rich, saturated colours, I adore the new varieties, such as Nemesia ‘Lady Lisa’, a bicolour purple and indigo blue, and the rich, deep, denim, ‘Lady Anne’. I’ve also fallen for the sweetly scented, but appallingly named ‘Fairy Kisses’.

The nemesias may need dead-heading and even more severe cutting back to one-third of their height after a truly scorching few days, but they will bud up and flower again. As they rest, the sweet potato Ipomoea ‘Solar Power Black’ swags the edge of the pot, with the salvia coming to the fore to take over the colour baton and carry it steadily until November. Any of the Mirage Series of Salvia greggii — either white, blue or cherry-red — are marvellous and, with all these families, new ones are appearing every year.

Whopper salvias such as ‘Amistad’ and S. involucrata ‘Hadspen’ flower brilliantly here until fireworks night at least, but they’re too tall for most pots. Even that has now been sorted with a new generation of breeding. I fell upon S. bodcious ‘Hummingbird Falls’. The equivalent in compact form of S. ‘Amistad’, this stands only 18in tall, but is still utterly handsome and healthy, even in a hanging basket.

Last, but not least, don’t forget the autumn-flowering bulb acidanthera. I love it either on its own in a pot or spearing its way up through a cloud of gaura. We have a series of those two in huge terracotta pots in our farmhouse garden right now and they’re looking dreamy.

Most of our phlox, persicarias and hydrangeas, the usual stalwart autumn performers, are looking indisputably wan this year even without the hose-pipe ban, so it’s to these ever-expanding families I shall be turning to in future to provide some late-season colour — and it’s a wonderful prospect.

'A Year Full of Flowers' by Sarah Raven is out now (Bloomsbury, £25)