Standing on the roof of the Sill with the wind in my hair, I have a new view of familiar countryside. For years I’ve driven along Hadrian’s Wall, enjoying the way the land forms a series of waves like a frozen sea.
Now, from the highest point of this building, I watch a buzzard circling above the Roman quarry at Barcombe Hill, see walkers labouring up the craggy steps at Steel Rigg, glimpse far-off bales in a recently cut hay field and cows tail flicking in the summer heat.
This is the National Landscape Discovery Centre in Northumberland national park. The building is named after the Great Whin Sill, a geological feature that the Romans made use of, building their wall atop its north-facing cliff.
About 295m years ago magma thrust its way up from the mantle, the molten rock forcing its way through weaker beds and cracks. Cooled into columns of dolerite, it runs in bands across Northumberland and Durham, dark, grey, hard, dramatic.
As whinstone weathers it creates thin, poor, soil with a specialised flora, known as whin grassland, that exists in just a few sites.
Replicating this community of plants on the roof of the Sill is a botanical experiment, one that has never before been attempted. A shallow ramp leads up through grass and wildflowers, turning in an angular spiral as it rises, the gradient copying the gentle slope of the sill itself.
The planting changes as it goes, so that it becomes a journey across Northumberland, from the betony, maiden pink and wild thyme of Hadrian’s Wall to the hare’s-foot clover and crow garlic of the salty coast.
These are plants that grow in short grazed turf between slabs of rock. To make a low-nutrient medium for these hardy species, bracken compost was mixed with soil from the floor of abandoned quarries. Sheep’s fescue and sweet vernal grasses grow through a protective coir mesh that will decompose in 18 months. Throughout are 10,000 plug plants grown from local seed.
On this blustery day, harebells bob wildly on the roof, fragile-looking but tough flowers of this demanding landscape.
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