The new autumn palette

Climate change is something that I learned about at school. It isn’t a new concept, though the impact of the shifting seasons, extreme weather events and new weather patterns are now starting to reach us in the sanctuary of our gardens.

For instance, when I was a child, we experienced so-called ‘April showers’ but these now seem to be a thing of the past, as does wrapping up in gloves and a scarf for bonfire night (it was actually rather cold in early November back then). Now, at the ripe old age of 36, I don’t recognise those weather patterns anymore.

Extreme weather events and new weather patterns are now starting to reach us in the sanctuary of our gardens

Similarly, the old habit of ‘putting the garden to bed’ feels irrelevant, and even

Artificially speeding up a plant’s growth, flowering or fruiting, usually by manipulation of temperature and light. Rhubarb and chicory can be forced in late winter by covering with a forcing jar or bucket, or by placing potted plants in the dark, to produce earlier, paler, sweeter growth. Hyacinths and other spring bulbs are often forced, so they flower earlier indoors.

Seasonal trends

© Jason Ingram

The Glasshouse Borders with Calamagrostis brachytricha AGM, Panicum virgatum ‘Shenandoah’ AGM and Eryngium agavifolium in autumn at RHS Garden Wisley

The general trends of climate change are delivering us wetter, milder winters and warmer, drier summers, but extreme weather moments are also very much a hurdle to be thrown at the gardener’s gate.

Wetter winters mean that simply gardening with Mediterranean plants isn’t the answer, nor is just gardening with plants that enjoy heat, as the ‘Beast from the East’ blast reminded us all a few winters back. Perhaps a new way to look at things in the garden could be to simply accept that some plants may perform for five to ten years, then give up?

Planting a diverse palette sets gardeners in good stead as some plants have known tolerance to extremes and others will surprise us.

© Nicola Stocken

Lagerstroemia ‘Tuscarora’

© Joanna Kossak

Nerine bowdenii ‘Bionce’

Enjoying a longer season

© Joanna Kossak

Salvia splendens ‘Jimi's Good Red’

I’m noticing two changes that draw the season out: the lack of early frost or any notable cold temperatures (these come several weeks later than I remember); and drought-dormant plants enjoying a ‘second wind’ in autumn when rain eventually arrives. This is pushing late-summer favourites on into the autumn palette, simply because of the change in growing conditions.

In the south-east of England especially, summer heat triggers earlier flowering of genera such as Hedychium and Lagerstroemia. Salvia have become firm autumn favourites in the Wisley Mixed Borders, and in recent years, both Salvia ‘Phyllis Fancy’ and Salvia splendens ‘Jimi’s Good Red’ flowered profusely until late November when the first proper frost clipped them back.

The latter was a selection that Helen Dillon (of Irish garden fame) received from Irish gardening celebrity Jimi Blake, and simply labelled it ‘Jimi’s good red’ as an aide-mémoir. It has since popped up in gardens across the country. In my opinion, many of the so-called ‘Mexican salvias’ (S. greggii, S. microphylla and their

A hybrid plant is the offspring produced by cross-pollinating one specific cultivar with another different cultivar. This process of cross-pollination, rather than pollination between plants of the same cultivar, generally creates stronger, healthier, improved offspring, said to have ‘hybrid vigour’.

Flowers to survive the frost

© Carol Sheppard

Ipomoea lobata AGM

© Graham Titchmarsh

Cobaea scandens f. alba

Make space for an obelisk or two, for while the thermostat stays above freezing, superb tender climbers that are often slow to get going, such as Cobaea scandens AGM (cup and saucer plant), including white variant f. alba, Ipomoea lobata AGM and Rhodochiton atrosanguineus AGM, will keep ploughing on with their stop-you-in-your-tracks, exotic-looking flowers.

A finale of flowers

© Philippa Gibson

Ceratostigma plumbaginoides AGM

A few plants begin flowering at the same time as their leaves change colour for autumn, which can be celebrated now too. The hardy plumbago, Ceratostigma plumbaginoides AGM, is readily available, though I prefer shrubbier C. willmottianum AGM. The crowning glory for flowers with dazzling autumn foliage (and the ultimate challenge to find and grow) is Franklinia alatamaha, one of Wisley’s most talked-about plants in autumn.

Equally fiery, Kniphofia caulescens deserves a mention, particularly its shockingly good autumn-flowering

Gardeners often use the word variety when referring to a specific plant, but the correct botanical term is 'cultivar'. Whichever word you use, it means a distinctive plant or plants, given a specific cultivar name and usually bred to enhance certain characteristics, such as flower or fruit size, colour, flavour or fragrance, plant size, hardiness, disease resistance, etc. Additionally, it is worth knowing that, botanically, variety has another meaning - it refers to a naturally-occurring distinct plant that only has slight differences in its looks. For example, Malva alcea var. fastigiata differs from typical plants by having an upright habit.

On a woody note, warmer summers and milder autumns have been a recipe of climatic success for Camellia sasanqua, seemingly Mother Nature’s best-kept secret. This camellia flowers in autumn with fragrant blooms. They’re a vast group, with many exciting cultivars that seem to be overlooked or completely unknown. Brilliant grown in a large pot, against a wall, or as a freestanding shrub, they’ll reward you with flowers throughout autumn until a significant frost stops them in their tracks.

© RHS / Tim Sandall

Franklinia alatamaha

Perhaps the least-expected plant for an autumn palette would be a magnolia, but a recent introduction of evergreen Magnolia grandiflora ‘November Fox’ is hailed to flower happily into autumn, even braving the November weather. However, it will take a few years to find its way to our garden centres, so I’m just getting to know it in the Wisley collection.

Of course, it would be remiss to sign off without mentioning the dahlia, surely the real royalty of late-summer tender plants that push their own boundaries into autumn. While I’m yet to see the tree species Dahlia imperialis flower outdoors this late in the year, it feels like it could become a distinct possibility sometime soon.

This page is an adaptation of an article published in the November 2022 edition of The Garden magazine, free to RHS members every month when you join the RHS.