| Knebworth Country Park Knebworth House | 153.89 ha | | — |
| Therfield Heath | 145.28 ha | | — |
| Kingswalden Park (Deer Park) | 65.99 ha | | — |
| Norton Common | 29.13 ha | | — |
| Weston Hills Local Nature Reserve | 17.09 ha | | — |
| Oughtonhead Common | 14.46 ha | | — |
| Ivel Springs Local Nature Reserve | 13.23 ha | | — |
| Purwell Meadows | 10.45 ha | | — |
| Great Ashby District Park | 10.41 ha | | — |
| Walsworth Common | 8.5 ha | | — |
| Butts Close | 6.03 ha | | — |
| Hitchin Priory Gardens | 5.53 ha | | — |
| New Wandon Park | 4.54 ha | | — |
| Howard Park and Gardens | 3.88 ha | | — |
| Ransom's Recreation Ground NHDC | 3.69 ha | | — |
| Blagrave Common | 3.66 ha | | — |
| Cow Plantation | 3.42 ha | | — |
| Avenue Park | 3.23 ha | | — |
| Ashwell Quarry & Quarry Springs Herts & Middlesex Wildlife Trust | 2.93 ha | | — |
| Windmill Hill | 2.91 ha | | — |
| Swinburne Park | 2.88 ha | | — |
| Bancroft Gardens | 2.47 ha | | — |
| Priory Gardens | 2.45 ha | | — |
| Wilbury Recreation Ground Hertfordshire County Council | 2.36 ha | | — |
| Broadway Gardens | 1.69 ha | | — |
| Walled garden | 1.44 ha | | — |
| Cadwell Playing Field | 1.29 ha | | — |
| Hexton Chalk Pits | 1.1 ha | | — |
| Ashwell Springs | 0.39 ha | | — |
| Barkway Chalk Pit | 0.37 ha | | — |
| Hill End Chalk Pit | 0.36 ha | | — |
| Parkfield Meadow | 0.34 ha | | — |
| Codicote Community Orchard | 0.26 ha | | — |
| Greencare @ Norton | 0.25 ha | | — |
| Triangle Community Garden | 0.16 ha | | — |
| Well Green | 0.16 ha | | — |
| Ashwell Quarry Springs Herts & Middlesex Wildlife Trust | 0.13 ha | | — |
| Letchworth Community Garden | 0.11 ha | | — |
| The Rose Garden | 0.1 ha | | — |
| The Walled Garden | 0.1 ha | | — |
| Halsey Green | 0.06 ha | 🐕 | — |
| Pond Gardens | 0.05 ha | | — |
| Seebohm Garden | 0.04 ha | | — |
| William Ransom Physic Garden | 0.03 ha | | — |
| Hawkins Wood | — | | — |