The gardens, which stand on what was once part of the Forest of Knaresborough, an ancient royal hunting ground, were started in 1950 by the Northern Horticultural Society (NHS) as a trial ground for growing plants in a northern climate. The RHS acquired the gardens in 2001 in a merger with the NHS. The gardens are known now for spectacular displays of color at every turn in the garden paths. Favorites include colorful candelabra primulas along a stream, blue poppies in the Meconopsis trial graden, and many different geranium species. Be sure to include the Alpine House on your must-see list.