It’s Brian Green’s last Journal as Editor, so I could only agree to his request to explain why Dulwich Park’s rhododendrons are so splendid (more so, he says, than some in local gardens).
Rhododendrons are a relatively old group of flowering plants, and members of the acid-loving ericaceous family. Most of the rhododendron species (there are over a thousand) occur on the slopes of deep-sided valleys bordering the Himalayas and southern Tibet, where they flourish, with small pockets elsewhere around the world. They are woodland plants which prefer damp, high rainfall climates with cool, mild temperatures, shelter, dappled shade and the well-drained, acidic conditions found in the forest floors on those slopes.
The American Garden was laid out by Lt Col Sexby in 1887 and planted in 1890/91, with the plant listing for the Park including 950 rhododendron, 1300 azaleas and 440 erica (heathers). American Gardens were so called because, in contrast to traditional English Gardens (think green and Capability Brown), they used colourful pIants such as rhododendron and other acid-loving plants originally brought back by explorers of the New World. In London there are examples at Kew, Richmond (the Isabella Plantation) and at Kenwood House in Hampstead, with Dulwich Park the only one still using the name.
In many ways the growing conditions in the beds of our American Garden are ideal for rhododendrons, and many of the original plants survive. The soil is damp from the rainwater run-off from Dawson Heights, rain itself is acidic and the trees at the edge of the Park provide some shelter. When planted, and until recently, large quantities of (acidic) peat were used - 1,500 cubic yards in the initial planting. General air pollution and nitrous oxide from vehicles will only have added to the acidity of local rain. Brian recalls that In the 1950s or early 1960s, Harry Carter, the Park Superintendent of the day, planted silver birches in the beds - despite opposition - to give them height, and these birches now partly provide the additional ingredient of dappled shade and shelter from the sun that the plants prefer.
Our rhododendrons have suffered from the warmer and changing climate in recent years, particularly our drier springs and the drought last summer, as well as competing with rampant brambles. Keeping these under control is no longer feasible as part of the routine park management contract, so, in recent years, groups from large corporates have helped to do so from time to time, as part of corporate social responsibility initiatives, to date with limited impact.