By John Hughes
The deciduous woodlands of North America are outstandingly rich in oaks. Out of this abundance, three species are to be met with in Dulwich: Red oak Quercus rubra; Pin oak Q. palustris; and Scarlet oak Q. coccinea.
The trunks of all three of these American oaks are smooth and silvery-grey, which is the simplest way to distinguish them from our two native oaks - English oak Q. robur and Sessile oak Q. petraea - both of which have much darker, ridged and knobbly bark. The leaves of all three American species are quite deeply cut in outline, with sharp bristles at their lobe ends, giving them a very different appearance from the wavy, sinuous outline of the leaves of our native trees. Both Red and Scarlet oak have the autumnal colouring one would expect from their names, though the degree of redness varies greatly, even on the same tree. The leaves of Pin oak can also turn fiery red in autumn, though on some trees and in some years they turn a rich brown instead.
Red oak has been cultivated in Britain since 1724 and is widely planted in Dulwich, as elsewhere in Britain. It was first recorded in the wild in 1942 and is becoming naturalised in a few places, especially on light, sandy soils in the south. Red oak has been frequently used by the Forestry Commission to provide much-needed colour along the edges of sombre spruce plantations. This is particularly the case in spring when the delicious yellow of its young leaves can be seen from miles away on clear days in the uplands. Two good examples of Red oak in Dulwich are the trees on the central greens of Frank Dixon Way and Close, both enlivened by having child’s swings attached.
Pin and Scarlet oaks are much less common, particularly the latter. I am not aware of any records of either tree from the wild. Both species have leaves with lobes cut more than halfway to the midrib, whereas those of Red oak are cut less than halfway and are in any event substantially bigger. The leaves of Scarlet oak are usually slightly longer and less deeply cut than those of Pin oak but this is not always the case. If in doubt, turn the leaf over. The back of a Pin oak leaf has obvious hair-tufts in the vein axils; that of a Scarlet oak either has indistinct or no hair-tufts on the back.
The best place in Dulwich to see mature examples of both Pin and Scarlet oak is College Road. There are two splendid Pin oaks, outside numbers 23 and 41. And there is a good Scarlet oak opposite the garage entrance to number 48.
In winter, without the leaves, any large tree with a silvery-grey trunk and possessing a cluster of buds at the twig tips (characteristic of all oaks) is likely to be an American oak. The buds of Red oak are dark reddish-brown, whereas those of Scarlet and Pin oak are a much paler brown. Winter is the best time to see the pin-like side spurs of Pin oak, from which it derives its common name. They can give the tree a spiny appearance.
Notable Trees of Dulwich - American Oaks
By John Hughes