Alan Eason of England originated this cultivar which is a seedling of H. rectifolia. Peter and Jean Ruh of Ohio registered it on Alan's behalf in 2005. 'Dartmoor Forest' is a large size plant about 27 inches high by 48 inches wide with dark green foliages. the leaves are slightly rippled, slightly cupped, slightly twisted, slightly corrugated and dull on top. Pale lavender, tubular flowers with stripes bloom from mid-July into August.