Heartwood Forest is a planned forest (woodland creation site) in Hertfordshire, England.The plans were set out in 2008 by the Woodland Trust to create the largest new forest of British native tree species of approximately 347 hectares (860 acres) in size.The site, near Sandridge, St Albans in the Metropolitan Green Belt, was formerly agricultural land (predominantly oilseed rape fields), but also currently contains around 18 hectares (44 acres) of remaining ancient woodland, which are integrated into the new woodland.