Rosie Fyles, Head of Gardens, at Chiswick House and Gardens, writes about gardens, nature, plants and people every month.

This month, the 37-degree shift in temperature over a fortnight that nobody is talking about… 

Written for The Chiswick Calendar

When winter and summer came together
It’s not that unusual to experience a frost in May. The traditional saying or proverb ‘Ne’er cast a clout till May be out’ warns of the naiveté of planting out young, tender plants before June arrives as you can get a cold May night that will stunt, stun and even kill some youngsters. You could also put on your summer clothes, pack up the winter warmers and get frozen yourself in a very cold wind if you don’t heed this warning. 

There has never been a May in my gardening life where a proper frost has occurred two nights running in London. On Sunday 10 May and Monday 11 May there were two nights of frost in the Chiswick House Kitchen Garden that caused a bit of havoc. The Duke of York’s potatoes (not that former Duke…) were hit hard and never recovered. The dahlia foliage blackened and wilted. The propagation greenhouse felt inappropriately chilled – windows shut tight and watering reduced. 

Thankfully the dahlias have recovered fully and are now preparing for their pomp.  

What happened next, after this double frost, felt unique. Over a period of two weeks the weather about turned and by 25 May the dahlias and their gardeners were roasting in 34.8 degrees. From a plant point of view this is potentially catastrophic. From a gardeners’ point of view this is a massive national news story. 

How did the Chiswick trees, plants and gardeners cope?
I observed that the work we have done over the last four years to adapt our gardening to extremes of weather, to become increasingly sustainable and to observe the plants’ needs not the calendar, stood up to this test.  

When I read in a national newspaper that our almost neighbours at RBG Kew estimated that they lost ‘200 trees’ during the heatwave, I am pleased to say we didn’t lose one – though we did lose potatoes… Some fortuitous forethought during past phases of tree planting mean we have a diverse tree collection, predicted to survive, thrive. 

What was inevitably hard was keeping recent, young planting alive. The protection they needed was from extreme heat now – not cold – and this meant a period of just over a week when watering these youngsters was our obsession. We are fortunate to have water harvesting on site, committed, patient and diligent volunteers. I am fortunate to have garden colleagues that heed survival instincts, rope in family watering reinforcements at the weekend and prioritise future flowers.   

It seems to have worked: the annual flowering mix in the Italian Garden, bringing more colour and diversity alongside the pink roses has survived the harshest of starts in life and is now looking robust and soon to flower. 

What should we do differently?
This experience has made me convinced that planting in autumn if possible is the only sensible, sustainable thing to do. Television advice, garden centre supplies and our own expectations need to change to encourage thinking ahead whenever we can to reduce the panic, minimise the strain on resources, humans and their plants and get things in the ground when it is more likely to be moist and welcoming and when temperatures are more likely to be stable. 

Having said this, I think our understanding of what’s sustainable and ‘the right thing to do’ will be constantly changing. Gardeners’ questions will become more complex and the answers to them less reliable. Our weather watching, our plant nurturing and care will only increase as extremes of weather become the unpredictable pattern. The gardeners’ need to educate and re-educate themselves will make us all lifelong learners, learning again and different, agile and resourceful, adapting constantly. Nobody will ever have all the answers… 

What I’m doing in my own garden this month:
Very little. Deadheading. Some Skimmia taming. Tying in climbing roses and clematis. I have been very busy at work. 

What to look out for in Chiswick House & Gardens: 
The new annual flower mix in the Italian Garden should start to show off in June. The roses are still stunning. Look out for the changing colours in the Kitchen Garden as Hollyhocks display their floral wares. And watch the beans climb while you are in there.