As the days shorten and weather begins to turn, Sally Petitt reflects on the importance of observing seasonal cycles in the garden this autumn – especially after a long summer of droughts and heatwaves.
One of the great benefits of being a horticulturist is the connection with the natural world, and this is true of anyone who spends time outside observing their surroundings, whether it be the plants in our gardens or in the wider landscape, migratory birds, or even the cycle of the moon.
During my horticultural career I have observed the inevitable seasonal shifts of flowering and fruiting, but also daylight hours, weather and the first mowing of lawns in spring. These observations can help with planning and maintaining a garden, no matter what size, but on a personal level they also help anchor me and provide a sense of calm.
For me, there is something humbling about the changes in the seasons, the weather and the gardening calendar. During the darkest and coldest winter days, there is always an optimism that days will lengthen, the light will brighten and temperatures rise, and with that comes the bursting of buds and spring blossom. In contrast, there is a point in autumn where the shortening days, cooling temperatures and turning of leaves indicate a time to tidy the garden, clear away the old and make way for the new.
Post-heatwave garden changes to look out for this autumn
In a garden, being in tune with seasonal shifts, or nature’s calendar, can influence what we grow and how we grow it, but we needn’t limit observations to the seasons.
Noticing a change in temperature and rainfall from one week to another can affect how we grow our plants and maintain our gardens. Low spring temperatures can impact sowing times for crops, while extended periods of drought influence not only watering regimes but also decisions about what we might grow in the future.
Today, in a changing climate, observing nature’s calendar is more relevant than ever. In the past, seasonal changes in temperature, rainfall and day length were generally predictable, but small variations in climate can result in a shift in timing of ecological patterns, wildlife behaviour and ecosystems. The succession of heatwaves this year, combined with a prolonged drought, has affected not only human behaviour but also our gardens, wildlife, landscapes, ecosystems and farming.
UK records show that oak trees now come into leaf one month earlier than they did in the 1950s, while snowdrops appear two months earlier than they did back then. For us as gardeners, this may mean a change in the appearance of our gardens, but for wildlife, such changes could be dramatic. Pollinators reliant on certain species for nectar might no longer have a food source, while insects that need oak trees for food or shelter may also struggle. In turn, the impact on food production may also be detrimental, with a fall in pollinators and periods of drought severely affecting crop yields.
Since 2022, we have been carrying out a Phenology Project at Cambridge University Botanic Garden in which we record leaf, flower and fruit development, along with leaf colouring and leaf fall in 90 tree species. Since the project started, we have noticed that there are definite shifts in the timing of these occurrences. As our data set increases, we will be able to build a picture to help us understand the effects of climate change and to grow and conserve plants in the future.
Adapting your gardening practices for a changing climate
As autumn creeps towards us, we can expect to see leaf colour, leaf fall, hedges full of hawthorns and sloes and the onset of the first seasonal frost. But this year, given extreme summer weather, autumn may not be as predictable as it once was, potentially resulting in less autumn colour, early leaf fall, fewer fruits in our hedgerows and fewer or less severe frosts than we may have experienced in the past.
While we may not be aware of it, gardeners are very much in tune with nature’s calendar. The impacts of any shifts in our seasons and weather may not be entirely predictable, but by observing seasonal biological changes in our own gardens, many of us are already adapting our gardening practices to suit a changing climate.
Sally Petitt is head of horticulture at Cambridge University Botanic Garden.
Images: Howard Rice
Is your garden ready for autumn? Get organised with our top gardening jobs for this month.