Hawthorn  (Crataegus monogyna)

Calcareous: containing free calcium carbonate, chalky.

1. National Biodiversity Network Species Dictionary (Feb 2003):
   http://www.nhm.ac.uk/nbn
   
2. Humphries. C.J., Press, J.R. & Sutton, D.A. (2000) Hamlyn guide to trees of Britain and Europe. Hamlyn, London.
   
3. Mabey, R. (1996) Flora Britannica. Sinclair-Stevenson, London.
   
4. Press, B. (1996) Collins Wild Guide: Trees. Harper Collins Publishers, London.
   
5. British Trees: hawthorn (Feb 2003):
   http://www.british-trees.com/guide/hawthorn.htm
   
6. Preston, C.D., Pearman, D. A., Dines, T.D. (2002) New Atlas of the Flora of Britain and Ireland. Oxford University Press, London.