Ancient woodlands have been around for centuries. In the UK they date back to medieval times, and have developed ecosystems that are rich, complex and irreplaceable. They are also a delight to visit, often with spectacular carpets of spring flowers. Dating woodlands is not straightforward but some plants can indicate that a site has been wooded for a considerable length of time. Guide to Ancient Woodland Indicator Plants, produced with the Woodland Trust, provides an introduction to these indicator plants.