Early Autumn Colour due to Hot Dry Spring

Autumn treesAutumn colour at RHS Garden Harlow Carr, Harrogate North Yorkshire; Photo courtesy RHS

Autumn colours are emerging in our gardens weeks early due to the hot dry spring say experts at the Royal Horticultural Society.

It is too early for decreasing day length, a key factor for British autumn colour, to have caused the yellow, red and brown tinges on trees at RHS Garden Wisley, including maples, Liquidambar styraciflua, Corylus (hazel nut) and Laburnum. The leaf colouring and leaf loss are due to dry soils left over from the spring.

At RHS Gardens at Rosemoor and Harlow Carr there are signs of autumn colouring on certain acers and at Rosemoor plants including Aesculus × neglecta 'Autumn Fire'
and Hydrangea serrata 'Tiara' (L) AGM are also taking on autumnal shades.

The fruit harvest at Wisley is also unusually advanced with September cultivars of apples, like 'Grenadier' and 'Laxton's Fortune', and 'Beth' pears ripening in the last fortnight. Autumn fruiting raspberries are peaking now instead of September.

Guy Barter, chief horticultural adviser at the RHS, says: "The autumnal leaf colouring and leaf loss on trees is due to dry soils."

There is a five inch soil moisture deficit this summer, despite some wet weather pushing it down to four inches for a week or two, so trees and shrubs are under water stress. However, it’s not fatal as they are well adapted and have had a good growing season."

The low soil moisture levels could lead to reduced flower formation in some vulnerable plants such as camellia and rhododendron, which set buds now. My current top tip is empty your water butts now to soak any vulnerable plants.

More unseasonable activity in the garden has been caused by mid-summer rain, leading to winter flowering plants blooming, including hellebores, Viburnum, Mahonia and magnolias, but this won’t impact on normal flowering season of November to April.

The RHS receives around 1,700 weather-related enquiries a year.

 
 

Article posted on 05 Sep 2011.