This year’s classic summer weather could herald a “spectacular” display of autumn colour – if the weather is settled in the next fortnight, the National Trust has said.

The organisation, which looks after many gardens, parklands and woods, said the sunny spell in late September and six months of high levels of sunshine have boosted the chances of trees putting on a great display of colour as their leaves turn.

Beautiful colours are still on the cards in spite of the heavy rain and strong winds that battered much of the country in the past weekend, but settled weather is needed over the next two weeks, the Trust’s experts said.

Although the very dry spring caused stress to some trees, “classic” summer weather with good levels of sunshine and rain has given most a good chance of keeping their leaves on until the colour starts to develop as temperatures drop.

The Trust said the warm, sunny summer increased the sugar content of the leaves, which results in a variety of colours from reds and oranges to browns and golds as the green chlorophyll breaks down in the autumn.

Acers starting to turn a deep red at Powis Castle, Powys in Wales (David Swanton/National Trust Images/PA)
Acers starting to turn a deep red at Powis Castle in Wales (David Swanton/National Trust Images/PA)

However, the weather now needs to be favourable throughout the first half of October to give the conditions for the best displays, with cold conditions at night, enough sunshine during the day and no intense storms or rainfall.

The conservation charity says it cares for more than 10 million trees in England, Wales and Northern Ireland, and one of the largest collections of ancient and veteran trees in the world.

Trust properties with spectacular displays include Stourhead in Wiltshire, where oaks, beech and lime are joined by more exotic specimens such as tulip trees and Japanese maple, and Sheffield Park in East Sussex, which has a collection of rare trees.

Simon Toomer, plant specialist at the National Trust, said: “Autumn in the northern hemisphere is one of the natural world’s great spectacles.

“It starts in the far northern deciduous forests and progresses southwards to the warm temperate regions over about a 10-week period.

Winkworth Arboretum is already seeing early autumn colour (National Trust/Hugh Mothersole/PA)
Winkworth Arboretum in Surrey is already seeing early autumn colour (National Trust/Hugh Mothersole/PA)

“Our northern gardens and woodlands are therefore a week or two ahead of the most southerly.”

While day length is the primary trigger for trees shutting down for the winter and shedding their leaves, weather conditions throughout the summer and early autumn affect the rate of leaf loss and intensity of colour, he said.

The best-known places for autumn colour are North America and Japan, and many National Trust parks and gardens have trees from these areas, he added.

“This variety of species ensures a long and very colourful display and this year, with favourable weather conditions, the show should be spectacular.”