| Panshanger Park Herts and Middlesex Wildlife Trust | 332.11 ha | | — |
| Woodhall Park | 162.91 ha | | — |
| Rye Meads | 61.76 ha | | — |
| Balls Wood Herts and Middlesex Wildlife Trust | 58.9 ha | | — |
| King's Meads Herts and Middlesex Wildlife Trust | 37.15 ha | | — |
| Rye Meads RSPB | 25.73 ha | | — |
| Pishiobury Park | 25.58 ha | | — |
| Southern Country Park | 23.36 ha | | — |
| Hartham Common East Herts District Council | 20.3 ha | | — |
| Waterford Heath | 17.43 ha | | — |
| Grange Paddocks | 16.13 ha | | — |
| Thorley Wash Nature Reserve Herts Wildlife Trust | 13.57 ha | | — |
| Hertford Heath Nature Reserve | 9.52 ha | | — |
| Sawbridgeworth Marsh | 9.28 ha | | — |
| Northern Parkland | 8.03 ha | | — |
| Lower Park Crescent | 6.22 ha | | — |
| Bat Willow Hurst Country Park East Herts District Council | 5.24 ha | | — |
| Link Road Woodland | 4.66 ha | | — |
| Bishop’s Park Playing Field | 3.37 ha | | — |
| Sworder's Field Bishop’s Stortford Town Council | 3.34 ha | | — |
| Thorley Wedge | 2.9 ha | | — |
| Castle Gardens East Herts District Council | 2.87 ha | | — |
| Datchworth Green | 2.73 ha | | — |
| Barrells Down Road Park | 2.6 ha | | — |
| Castle Grounds East Herts Council | 2.51 ha | | — |
| Willowmead Herts and Middlesex Wildlife Trust | 2.42 ha | 🐕 | — |
| King George's Field | 2.19 ha | | — |
| Wooden Park | 2.19 ha | | — |
| The Barrons Park | 2.17 ha | | — |
| Walled Gardens | 2.16 ha | | — |
| The Meadow | 2.08 ha | | — |
| Brickendon Green | 1.62 ha | | — |
| Manor Farm | 1.62 ha | | — |
| Parsonage Playing Field | 1.44 ha | | — |
| Cannons Close Park | 1.39 ha | | — |
| Bishop's Park Playground | 0.96 ha | | — |
| Cooles Park | 0.83 ha | | — |
| Waytemore Road Park | 0.76 ha | | — |
| Millennium Wildlife Area | 0.75 ha | | — |
| The Firs | 0.72 ha | | — |
| Layston Court Gardens | 0.62 ha | | — |
| Northolt Avenue Park | 0.53 ha | | — |
| Beacon Park | 0.49 ha | | — |
| Dimsdale Crescent Park | 0.41 ha | | — |
| Monastery Gardens | 0.38 ha | | — |
| Ward Cresent Park | 0.32 ha | | — |
| Burley Road Park | 0.3 ha | | — |
| F&B Conservation Area Fawbert & Barnard School | 0.26 ha | | — |
| Larkshill | 0.25 ha | | — |
| Great Munden Recreational Garden | 0.21 ha | | — |
| Knebworth Court | 0.2 ha | | — |
| Stable Gardens | 0.11 ha | | — |
| Grandma's Garden | 0.06 ha | | — |
| St Leonard's Garden Hertford Town Council | 0.05 ha | | — |
| Wilson Close Park | 0.04 ha | | — |
| Thieves Lane Community Garden | 0.02 ha | | — |
| Ashridge Common | — | | — |
| Bandy Common | — | | — |
| Bromley Common | — | | — |
| Burleigh Common | — | | — |
| Cottonborough Common | — | | — |
| Fellowsfield Common | — | | — |
| Goldsdell Common | — | | — |
| Great Brookfield Common | — | | — |
| Halfyard Common | — | | — |
| Hartham Common | — | | — |
| Hunsdon Mead | — | | — |
| Lamsden Common | — | | — |
| Sander's Green | — | | — |