The Oak tree, probably the most recognised and loved tree in Britain, is well represented in Dulwich, both as old field boundary marks and ornamental specimens
Of our two native species, the English Oak, (Quercus robur), has acorns on stalks, while the Sessile Oak (Quercus petraea) has acorns without stalks. Not every year is a good acorn year but both species support a huge variety of insects and wild life while remaining healthy and vigorous. The familiar ‘oak apples’ are the result of a parasite wasp laying eggs on twigs, causing a ‘gall’. This growth is a source of tannin, used in colouring blue/black ink.
There is a magnificent example of a Turkey oak (Quercus cerris) in the Park, near the old tennis courts, marked as one of ‘The Great Trees of London’, with a spread in full leaf of about 130’. These were introduced in the 18th century, but do not support such a rich wild life. The wood is not good to work with, splitting and breaking. Of course the timber of our great oaks is famous for strength, for building and furniture.
There are several oaks from the United States in the Park and along College Road, which colour splendidly in autumn, and one, the Red Oak (Quercus borealis) is sensational in spring too, its foliage emerging a clear bright
yellow, lasting for several weeks, before gradually turning green and then colouring brilliantly red in the Autumn
The evergreen Holm Oak (Quercus ilex), naturalised here from the Mediterranean, is our largest evergreen tree, a very deep green indeed, casting a heavy shade. It tolerates salt winds, provides valuable shelter belts, and despite its size produces tiny acorns, but in spring it can be covered in golden catkins, an amazing transformation.
Another oak, becoming popular as a landscape feature, is the Cypress oak, a natural variant of Quercus robur, from Central Europe. Tall and columnar in habit, (there is one in the Park near the big weeping Willow by the stream), and there is a 20 strong avenue planted on one side of the Windrush Square, in Brixton