Ancient woodland indicator species growing in Welwyn Garden City town centre

For a few short weeks our woodland flowers come into bloom, making the most of the springtime light whilst the canopy leaves are still dormant or just beginning to unfurl.  Some of these plants are recognized as being specific to woodlands that have been in continuous existence from ancient times, possibly as far back as the re-colonisation of the British Isles by trees after the last Ice Age. They are plants that have adapted to woodland conditions: although they do grow elsewhere, they find it difficult to do so.  They do not establish quickly in newly created woodland on former farmland, or spread readily from ancient woodland to neighbouring isolated woods.  The more indicator species present in a woodland, the more likely it is that it has been undisturbed for a very long time. 

Why is an ancient woodland indicator species growing on the grass verge next to the Campus in Welwyn Garden City? 

Sometimes these plants indicate the vestige of an ancient woodland.  The grass verge in question was once part of Sherrardspark Wood (we know this from old maps) and it may be that some elements of the conditions that were present in the former wood persist, even though the verge is constantly mown and may have been fertilized.  Perhaps the shade of the remaining trees enables the plant to cling on, discouraging other more vigorous species from invading its niche. This plant is called Goldilocks and it is a woodland buttercup (characterized by whorls of needle-like upper leaves).  It grows in a few places within the current boundaries of Sherrardspark Wood in quite shady conditions.

Some of these ancient woodland indicators are famous for carpeting many a woodland floor, and in Sherrardspark Wood we have good drifts of Bluebells and Wood Anemones.  Dog’s Mercury has insignificant pale flowers but is one of the first ground cover plants of the year to “green up” the woodland floor, especially on the chalkier soils on the margins of the wood.

Other flowering plants that make their home in our woods are best seen along the sides of the paths and rides. The margins of these paths are cut annually to keep the nettles and brambles at bay, allowing less vigorous plants to thrive. Dog Violets and Early Dog Violets, Bugle, Wood Speedwell and Yellow Pimpernel hug the ground and have small but colourful flowers. However, Wood Sorrel, Pignut, Sanicle and Moschatel (known as Town Hall Clock because of the arrangement of its flower clusters), are hard to spot as they are tiny with small white flowers and are only found in a few locations in our woods. 

Yellow Archangel grows in the wood in a few places but we also have large expanses of its cultivated relative, Variegated Yellow Archangel, which has been dumped in the woods at various locations. The original is relatively prolific as it can reproduce via runners but the garden variety does this with far more vigour.  The original is a small compact spire with thin pointed dark green leaves and yellow hooded flowers arranged in a whorl around the stem. The garden escape variety has broader leaves that are part green, part silver sheen (in fact it has been cultivated for its foliage) and it tends to heap up upon itself. Although a good nectar source for bees, its control is high on the Work Party to-do list.  The same is true as of Spanish Bluebell.  We need to be vigilant because it hybridizes with our native English Bluebells. 

Other woodland indicator plants include the grasses: Wood Millet and Wood Melick; the sedges:  Pendulous Sedge and Remote Sedge; and the rushes: Great Wood-rush and Hairy Wood-rush. The sedges and rushes are well represented especially on wood banks.  Broad Buckler Fern is fairly frequent throughout the wood and Hard Fern has a few niche locations.

The presence of these ancient woodland plants in Sherrardspark Wood is broadly consistent with findings of floral surveys carried out over the last hundred years. Our task is to manage the woodland so that they continue to thrive.

Please visit our picture gallery to see more photographs of the ancient woodland indicator species mentioned in this article.

Charlotte Fox
Wood Warden

May 2017

 

 

Goldilocks Buttercup (Ranunculus auricomus). Photo Charlotte Fox

Bluebells (Endymion non-scriptus). Photo Marian Dawson

Yellow Pimpernel (Lysimachia nemorum). Photo Charlotte Fox

Wood Sorrel (Oxalis acetosella). Photo Chris Cooke