In reply to Lankyman:
There's a Happy Valley near me. Famous for herbs but not, I think, the sort you mean...
"The 67-hectare (170-acre) site is a steeply sided valley with large areas of grassland and wooded slopes. The diverse chalk grasslands on the eastern and north-western sides are rich in many species of herb which are uncommon in London, and the nationally scarce man orchid and round-headed rampion have also been recorded. Devilsden Wood on the western side has a canopy of ash, oak and hazel. Trees such as midland hawthorn and plants such as sweet woodruff are characteristic of ancient woodlands."