10-Sept September’s Shifting Shades

In early September anyone wandering around a London park might be surprised how little other colours there were other than all the different shades of green. Even at Wisley, where there is a substantial collection of rare trees, there is still a surprising lack of colour. However, as the month progresses soft browns and yellows start to creep into the landscape. One of the first to be noticed are the elms which now start to turn a variety of the dullest yellows. There are as yet no changes to be seen in the beeches of Burnham beeches but the famous hornbeam woods of Epping forest are now starting to slowly yellow.

In other species such as some of the ashes and box elder the pigments just seem to be slowly washing away. This is also true of elderberry, which was one of the first leaves to unfurl in the spring. Now its leaves are a sickly yellow, sometimes with various washed out pinks, greens and purples.

Towards the middle of the month there is still a surprising lack of colour generally, considering autumn colour will be at its peak in four weeks time. Trees such as apples, pears, poplars and honey locusts are all getting quite dappled. Honey locust even have separate green and lemon yellow leaflets. Wild bullaces, which were quite difficult to find in the spring, now stand out with their separate butter yellow and green leaves. Other trees that become noticeably dappled are Lombardy poplars and Caucasian wingnuts whose leaves are now flecked with acid yellow.

In other species such as some of the ashes and box elder the pigments just seem to be slowly washing away. This is also true of elderberry, which was one of the first leaves to unfurl in the spring. Now its leaves are a sickly yellow, sometimes with various washed out pinks, greens and purples.

Towards the middle of the month there is still a surprising lack of colour generally, considering autumn colour will be at its peak in four weeks time. Trees such as apples, pears, poplars and honey locusts are all getting quite dappled. Honey locust even have separate green and lemon yellow leaflets. Wild bullaces, which were quite difficult to find in the spring, now stand out with their separate butter yellow and green leaves. Other trees that become noticeably dappled are Lombardy poplars and Caucasian wingnuts whose leaves are now flecked with acid yellow.

A wet early autumn means less sunlight which in turn means fewer reds. The American red oaks are often the first to be noticed on account of their habit of allowing a single large branch to turn a dramatic red whilst the rest of the tree remains perfectly green. Pin, red and scarlet oaks are all trees associated with the famous “fall” colours along the east coast of America.

Although rarely grown together, all three can be seen side by side in Beales arboretucm. There is also one of the best trees for autumn colour there, the ‘Splendens’ cultivar of the scarlet oak. As a group, these oaks tend to be large trees and so in London they seem confined to the larger parks and gardens e.g. Syon, Osterley, Kenwood, Holland and Battersea parks.

Maples including our own wild maple Acer campestre are also starting to change colour. In many maples it is the leaf margins that change first, just as it is the leaf veins that often change first in cherries. Maples generally turn a variety of soft reds, yellows and greens but Japanese maples tend towards a much greater range of reds including coral and flame red as well as scarlet. The ubiquitous sycamore, which is just a large maple, once again disappoints, now having just leaves with shrivelled edges.

As the month progresses every street seems to have a cherry tree showing a range of soft reds. More fiery reds with some orange usually indicates the widely planted Sargent’s cherry. Other cherries that particularly colour well, such as the Fuji cherry Prunus incisa and the Tibetan cherry P. serrula deserve a wider planting. Natural street trees such as the upright forms e.g. Prunus x hillieri spire should also be planted more.

Meanwhile, going largely unnoticed are the vast numbers of common limes Tilia x europaea which all seem to have dirty leaves turning the softest yellow. Other limes, even one of the parents of this hybrid i.e. the large-leaved lime T. platyphyllos have yet to colour. The rare American lime T. americana in Hyde park and the Mongolian lime T. mongolica in Cannizaro park produce much better yellows. One of the most unusual colour changes of the whole autumn occurs this month in red horse chestnuts. Unlike common horse chestnuts, which are already losing their leaves and even showing next year’s buds, the leaves of the red horse chestnuts are developing an almost metallic bronze sheen unlike any other tree. Various purple cultivars such as those of Norway maple, sycamore and myrobalan plum all now seem to be turning deeper shades of purple, making them stand out even more.

As the month comes to its end, some forms of Persian ironwoods start to show particularly bright reds, brown and yellows. They will hold these colours for far longer than most other trees. Silver maples are turning a similar range of colours but in this case far more muted rose reds, watery yellows and translucent greens. Meanwhile oak, beech, hazel and magnolias all remain as yet unchanged.