Stocker's Lake is an old flooded gravel pit of approx 90 acres (37.5ha) at Rickmansworth, Hertfordshire, England, within the Colne Valley Regional Park which is designated as a Local Nature Reserve.
Old Park Wood is a 16.7-hectare (41-acre) Site of Special Scientific Interest in Harefield in the London Borough of Hillingdon. The south-east part is an 8-hectare (20-acre) nature reserve owned and managed by the Hertfordshire and Middlesex Wildlife Trust.
Mid Colne Valley is a 132 hectare biological Site of Special Scientific Interest in Harefield in the London Borough of Hillingdon and Denham in South Buckinghamshire. Its main importance lies in its extensive diversity of birdlife in lakes in former gravel pits.
Waterford Heath is a 35.2 hectare Local Nature Reserve in Waterford in Hertfordshire, England. It is owned by Lafarge Tarmac and managed by the Herts and Middlesex Wildlife Trust together with East Hertfordshire District Council and Lafarge.
Balls Wood is a 58.5-hectare (145-acre) nature reserve managed by the Herts and Middlesex Wildlife Trust in Hertford Heath in East Hertfordshire. The wood was purchased by the Trust from the Forestry Commission.
Hertford Heath nature reserve is a 28 hectare biological Site of Special Scientific Interest in Hertford Heath in Hertfordshire. It is managed by the Herts and Middlesex Wildlife Trust and the local planning authority is East Hertfordshire District Council.
Stanborough Reedmarsh is a 3.3 hectare Local Nature Reserve in Welwyn Garden City in Hertfordshire. It is owned by Welwyn Hatfield Borough Council and managed by the Herts and Middlesex Wildlife Trust.
Tewinbury is a 7.5-hectare (19-acre) biological Site of Special Scientific Interest near Tewin in Hertfordshire. The local planning authority is East Hertfordshire District Council, and the site is managed by the Herts and Middlesex Wildlife Trust
Uxbridge Alderglade is a 2.9-hectare (7.2-acre) nature reserve in Uxbridge in the London Borough of Hillingdon. It is managed by the Herts and Middlesex Wildlife Trust.
Pryor's Wood is an 8.7-hectare (21-acre) nature reserve in Great Ashby, near Stevenage in Hertfordshire. It was formerly managed by the Herts and Middlesex Wildlife Trust (HMWT). In February 2016 HMWT announced that three sites, Barkway Chalk Pit, Hill End Pit and Pryor's Wood, which HMWT managed on behalf of their owner, North Hertfordshire District Council, were to return to Council management as the Trust was no longer able to meet the cost.
Broad Colney Lakes is an 11 hectare nature reserve previously managed by Herts and Middlesex Wildlife Trust in London Colney in Hertfordshire. It has recently been sold to an anonymous buyer but reports in The Herts Advertiser says "the selected buyer has stated that the site will continue to be used for fishing, with the woodland managed for the benefit of wildlife.” It has three lakes, created as a result of gravel extraction in the 1920s. Otters travel through Long Lake on their journeys along the River Colne, which flows through the lake, and great crested grebes nest at the edge. Small Lake is marshy and a breeding area for fish, while North Lake has tufted ducks, coots and mallards.
Purwell Ninesprings is a 6.4-hectare (16-acre) nature reserve managed by the Herts and Middlesex Wildlife Trust on the edge of Hitchin, Hertfordshire, England.
Stocking Springs Wood is a 1.1-hectare (2.7-acre) nature reserve between Ayot St Lawrence and Ayot St Peter in Welwyn Hatfield district in Hertfordshire. It is managed by the Herts and Middlesex Wildlife Trust.
Hilfield Park Reservoir is a 76.3 ha construction built in 1953 between Bushey and Elstree in Hertfordshire, and owned by Affinity Water. Declared a Local Nature Reserve (LNR) in 1969, it is managed by the Herts and Middlesex Wildlife Trust (HMWT). It is the oldest LNR in Hertfordshire.
Oughton Nature Reserve in Hitchin in Hertfordshire is managed by the Herts and Middlesex Wildlife Trust. The 6.2-hectare site on the north bank of the River Oughton is not publicly accessible, but it can be viewed across the river from Oughtonhead Common.
King's Meads is a nature reserve between the towns of Hertford and Ware in Hertfordshire. It is managed by the Herts and Middlesex Wildlife Trust, and with an area of 96 hectares it is the largest of the Trust's reserves. The site has been registered by the Trust as Common land, but the registration for some areas was disallowed due to objections.
Long Deans is a 15 hectare nature reserve managed by the Herts and Middlesex Wildlife Trust in Nash Mills, between Kings Langley and Hemel Hempstead in Hertfordshire. It is neutral and chalk grassland and woodland with beech, ash, oak and wild cherry. Birds include common linnet, common bullfinch and song thrush, and the site is home to bats.
Fir and Pond Woods is a 29 hectare nature reserve in Potters Bar in Hertfordshire. It is managed by the Herts and Middlesex Wildlife Trust. It is two separate woods, with Fir Wood connected by a short footpath to the large Pond Wood to the south.
Gobions Wood is a 36 hectare nature reserve managed by the Herts and Middlesex Wildlife Trust in Brookmans Park in Hertfordshire. The site was formerly owned by the Gobions Woodland Trust, a registered charity which was closed down in 2013 because it had ceased to exist.
Lemsford Springs is a 4 hectare nature reserve in Lemsford, Hertfordshire, England. It is managed by the Herts and Middlesex Wildlife Trust, which purchased the site in 1970. Notable for its lagoons, the site is in the Lea valley and its other habitats are meadow, hedgerows, marsh and willow woodland.
