A new space at the RHS garden in Devon is addressing climate change
Heavy sporadic rainfall has always been a feature of the weather in Devon, so when Jonathan Webster, curator of RHS Rosemoor, commissioned Jo Thompson MSGD to design a new garden for this popular visitor attraction, managing extreme water run-off was a key element of her brief.
Credit: Global Media
The site had formerly been home to the Spiral Garden, designed by Tom Stuart-Smith MSGD in 1991, which although it had stood the test of time, was felt to be due a contemporary update. As well as carrying a climate-change message, the new Cool Garden is intended to provide a calm visual contrast to the adjacent Hot Garden, with a plant palette of blue, white and pastel-coloured flowers and grey foliage.
Managing extreme rainfall was the key driver behind the design concept. The naturally sloping site had previously been terraced, so Thompson decided to reinstate the slope, basing her curving design on the contour lines of the site survey. “Working with the natural terrain allowed me to turn a problem into a feature, since that is how water wants to flow. And I do like the aesthetics of a curving rill, although not the construction,” she says. “The resultant ramps and slopes also helped make the entire garden accessible to all visitors, regardless of physical ability.” Paths in the lower section are water-permeable resin-bound gravel to reduce water run off, and the curved wall at the top of the garden is a dry stone construction by Rural Stonework & Landscapes of Barnstaple, using stone from Trebarwith Stoneworks.
The water features were designed to give the impression that there is a direct flow from five water blades set into a low drystone wall at the top of the garden, into an upper pool then down through curving shallow rills which ‘disappear’ underground before emerging in the large pond at the lowest point of the site. In reality, the upper canal is self contained, and both independent bodies of water are supported by large balancing tanks. “Water Artisans did an amazing job of the complex calculations and construction. Depths vary, from 20cm in the top pool to a couple of millimetres in the rills (where people can’t resist paddling), to a maximum of 90cm in the lower pool.”
There are around 3,000 plants in the garden, many of which were ‘recycled’ from the original design by Stuart-Smith, including a large selection of hemerocallis and wildlifefriendly buddlejas. To protect the soil from degradation by the heavy rainfall, Thompson used groundcovers including Artemisia schmidtiana ‘Nana’, which forms neat mounds of finely cut silvery foliage.
Height comes from a number of neatly pyramidal Betula pendula ‘Fastigiata Joes’ (‘Jolep 1’). “Willows might have seemed like the obvious choice in a garden focused on water, but I was concerned about their roots interfering with the paving over the long term. I didn’t want trees with a heavy leaf fall, which would have caused ongoing maintenance issues for the ponds. Birches were the obvious choice, because they have a neat habit, a sympathetic character and they form a visual link with other specimen birch trees visible in the wider garden.”