In the United Kingdom, ancient woodland is that which has existed continuously since 1600 in England, Wales and Northern Ireland. Planting of woodland was uncommon before those dates, so a wood present in 1600 is likely to have developed naturally.

Ficaria verna, commonly known as lesser celandine or pilewort, is a low-growing, hairless perennial flowering plant in the buttercup family Ranunculaceae. It has fleshy dark green, heart-shaped leaves and distinctive flowers with bright yellow, glossy petals. Native to Europe and Western Asia, it is now introduced in North America, where it is known by the common name fig buttercup and considered an invasive species. The plant is poisonous if ingested raw and potentially fatal to grazing animals and livestock such as horses, cattle, and sheep. For these reasons, several US states have banned the plant or listed it as a noxious weed. It prefers bare, damp ground and is considered by horticulturalists in the United Kingdom as a persistent garden weed; nevertheless, many specialist plantsmen, nursery owners and discerning gardeners in the UK and Europe collect selected cultivars of the plant, including bronze-leaved and double-flowered ones. Emerging in late winter with flowers appearing late February through May in the UK, its appearance across the landscape is regarded by many as a harbinger of spring.