The changing nature of parks and gardens makes their character and historic interest rather difficult to protect. Replanting, pruning and trimming are constant activities, and gardens are in a continual process of change, from one month to the next, and from one season to another. Under the system designed to protect historic buildings and monuments, scheduling a garden or landscape might prevent change to the structure, but it would also inhibit its management so it can only be used to protect individual features and derelict gardens. Listing can only be applied to its built features such as follies, walls and bridges.
Some recognition of the lack of protection for historic parks and gardens was made in 1983 when the National Heritage Act enabled non-statutory registers to be compiled of historic gardens in England and Wales, and similar provisions were subsequently made in Scotland and Northern Ireland. All UK planning authorities are now encouraged to include policies in their development plans for the protection of designed landscapes and to protect these 'registered' historic parks and gardens. There are also statutory procedures for consultation where development is likely to affect a registered historic park or garden, and the Garden History Society is consulted on all applications in England, Scotland and Wales. However, inclusion on the registers, which are listed below, does not bring any additional protection, and alterations to parks and gardens generally do not require statutory consent unless they involve development work requiring a planning application, listed building consent, or scheduled monument consent, or they affect a tree covered by a tree preservation order.
The Register of Parks and Gardens of special historic interest in England is maintained by English Heritage and now contains almost 1,450 sites, graded like listed buildings, with grade II denoting national importance, II* being 'of exceptional interest' and I (accounting for 10 per cent of entries) denoting international importance. English Heritage is consulted on all applications affecting gardens of grades I and II*.
The Register of Parks and Gardens of special historic interest in Wales is maintained by Cadw and ICOMOS and is similarly structured (again with 10 percent at grade I). It now contains over 370 entries. Statutory consultation procedures are being reviewed.
An Inventory of Gardens & Designed Landscapes in Scotland was introduced in 1988, initially with 275 sites, and is maintained by Historic Scotland. Limited protection was granted to these sites in 1992 under the Town & Country Planning (General Development Procedure) (Scotland) Order (GDPO), making them a material consideration in the planning process. Any planning proposal which would affect an Inventory site must be referred to Scottish Ministers through Historic Scotland and Scottish Natural Heritage. Supplementary Extension Inventory volumes have since been prepared for some areas of Scotland and there are now over 340 sites included, but unfortunately the GDPO definition only covers the 275 sites which were included in the Inventory in 1988.
In Northern Ireland the Register of Historic Parks, Gardens and Demesnes of Special Historic Interest, which is published by the Environment and Heritage Service, includes 154 sites. The entries are not graded. A further 150 sites have been identified as having a high level of interest and are included as an appendix to the main Register as designated 'Supplementary' sites.