Herts and Middlesex Wildlife Trust manages over 40 nature reserves covering nearly 810 hectares north of London, in Hertfordshire and the historic county of Middlesex, part of which is divided between the London boroughs of Barnet, Enfield, Harrow and Hillingdon. It has over 21,000 members, and is one of 46 Wildlife Trusts across the UK. It is a Registered Charity, with its Registered Office in St Albans, and had an income in the year to 31 March 2014 of over £1.5 million.
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.
Darland's Lake Nature Reserve is a nature reserve south of Totteridge Village in Barnet, England. It is owned by the London Borough of Barnet and was managed from 1971 by the Hertfordshire and Middlesex Wildlife Trust, and more recently by the borough council. In 2007 the council spent £215,000 on repairing the dam and other works, and then proposed leasing the reserve to the Wildlife Trust. The transfer did not take place and in September 2017 a trust was set up by the London Wildlife Trust and local residents associations which took over the management of Darland's Lake. In 2020 Darlands Conservation Trust launched an appeal to raise £450,000 for excavation to prevent the lake drying up.
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.
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.
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.
Hill End Pit is a 0.7-hectare (1.7-acre) nature reserve on the site of a former chalk pit, in St Paul's Walden in North 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. It has the largest colony of Azeca goodalli snails in Hertfordshire. Plants include viper's bugloss, cowslip and marjoram, there are butterflies such as common blue and gatekeeper, and many birds including woodpeckers.
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.
Marshalls Heath is a hamlet and a 4-hectare (10-acre) Local Nature Reserve in Wheathampstead parish, Hertfordshire, England. The nature reserve is owned by Wheathampstead Parish Council and managed by the council together with the Friends of Marshalls Heath. It was purchased from The Queen's College, Oxford, in 1966.
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.
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.
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.
Longspring Wood is a 1.2-hectare (3.0-acre) nature reserve managed by the Herts and Middlesex Wildlife Trust in Kings Langley in Hertfordshire.
Danemead is a 5.6-hectare nature reserve west of Hoddesdon in Hertfordshire, managed by the Herts and Middlesex Wildlife Trust. It is part of the Wormley-Hoddesdonpark Wood North Site of Special Scientific Interest.
