Retaining hedgerows inside a development layout

Retained hedgerows disappear quietly. They survive the layout, they survive construction, they get shown on the approved landscape plan, and then they are gone within five years of occupation because they sat on the rear boundaries of private gardens where nobody had a duty to keep them. Designing a layout that actually keeps its hedgerows means putting them where they can be managed, not where they are convenient to draw.

Why retained hedgerows are lost after occupation

Three mechanisms account for almost all the losses, and none of them involves a breach of condition.

A hedge on a rear garden boundary is under the control of the resident, who wants a fence, a trampoline and light on the lawn. Unless the condition and the transfer restrict it, removal is lawful and unenforceable in practice. A hedge along a plot side boundary fares slightly better because it is more visible, but it gets reduced to a height that removes most of its structure.

A hedge in an unadopted verge with no named manager gets nobody's attention until it obstructs a footway, at which point it is cut hard. And a hedge whose root zone was compacted during construction dies back over several seasons, so the loss reads as natural decline rather than damage.

The design response follows directly. Put retained hedgerows in public open space, on public frontages, or in managed green corridors with an identified manager and a funded management plan. Keep them out of private rear gardens wherever the layout allows it.

Root protection for a hedge line

BS 5837:2012 is written for trees, and its root protection area calculation is based on stem diameter. A hedge has no single stem, so the standard does not give you a formula.

What works in practice is a construction exclusion zone defined by the arboriculturist as a continuous strip either side of the hedge centre line, fenced to the standard for tree protection, with the width set by the hedge's size, species and any hedgerow trees within it. Hedgerow trees are assessed individually under BS 5837 and their root protection areas often extend beyond the hedge strip, which sets the controlling dimension.

Three site practices decide whether the hedge survives the build:

• The exclusion fence goes up before any plant arrives on site and stays up until the last operation in that area is complete.
• No storage, no mixing, no spoil, no site road and no service trenching inside the zone, with any unavoidable service crossing done by trenchless methods at a position agreed in advance.
• Level changes stopped outside the zone, because raising ground over a hedge root plate kills it as reliably as cutting through it.

Include these in the Arboricultural Impact Assessment and its method statement rather than in a general note on the planting drawing. Getting the protective measures signed off promptly is its own exercise, covered in our note on discharging a tree protection condition without delay.

Rear boundary against public frontage positions

Where the hedge sits in the layout is the single most powerful decision available, and it is made at the masterplanning stage.

A layout that faces development onto a retained hedgerow, with a footpath or a lightly trafficked lane between the buildings and the hedge, keeps the hedge in view and in management. A layout that backs onto it does the opposite.

There is a cost to this. Fronting onto a hedge uses more land per unit than backing onto it, and a developer will feel that in the density. It is a real trade-off, and the answer depends on how much the hedgerow contributes to the scheme's biodiversity and character case.

Gaps for access and the cumulative effect

Every driveway, footpath and visibility splay takes a bite out of the hedge, and the bites are assessed individually while the effect is cumulative.

Two consequences follow. The linear length of hedgerow is reduced, which shows up directly in the biodiversity metric, and the continuity of the hedge as a commuting route for bats and a corridor for small mammals is broken. A hedge cut into eight segments by driveways is a different habitat from a continuous hedge of the same total length.

Reduce the number of crossings by grouping access: shared private drives serving three or four plots rather than individual crossovers, and footpath links consolidated at fewer points. Where a crossing is unavoidable, keep it narrow, and consider a raised crossing over a retained root zone rather than a cut.

Visibility splays are the hardest to argue. The highway authority will require them, and a splay across a hedge means reducing its height in that length. Negotiate the position of the access rather than the splay dimension, and check whether a lower speed limit or a change in access geometry reduces the requirement.

Species diversity and habitat connectivity value

Hedgerow value is not uniform, and the survey should distinguish.

The Hedgerows Regulations 1997 importance criteria turn partly on the number of woody species in a 30 m length, along with age, associated features and historical significance. A species-rich hedge on an old boundary line is a different proposition from a single-species hawthorn planted in the 1980s, and the layout should protect them differently.

Connectivity matters as much as composition. A hedge linking a woodland to a watercourse is worth more than an equivalent hedge with both ends in an arable field, and losing the linking length has an effect beyond the metres removed. Record the connections in the ecology baseline as well as the hedge itself.

Under the Environment Act 2021 regime, hedgerows are measured as a separate linear habitat in the statutory biodiversity metric, with their own gain requirement and their own trading rules. Hedgerow units cannot be satisfied by area habitat creation elsewhere, so a scheme that removes hedgerow length has to replace hedgerow length. That arithmetic belongs in the Biodiversity Net Gain Assessment at the layout stage rather than after the plan is fixed, and the statutory metric is work for a competent person under the 2021 Act, with the biodiversity gain plan approved by the local planning authority.

Management responsibility and adoption

A retained hedge needs a named manager, a specification and money, and the planning submission should identify all three.

The realistic options are transfer to a management company funded by an estate charge, adoption by the local authority or parish council where it is willing, or retention by the developer under a long-term arrangement. Each has drawbacks. Management companies change hands and cut costs. Councils are reluctant to adopt anything that carries a liability. Developer retention ends when the last plot sells.

Whatever the route, the management plan needs to specify the cutting regime and cycle, the season, the height and width to be maintained, gap replanting, and the treatment of hedgerow trees. Cutting on a two or three-year rotation, in sections, produces more berries and more structure than annual flailing, and it costs less.

The timing constraint is statutory. Under the Wildlife and Countryside Act 1981 it is an offence to damage or destroy the nest of a wild bird while in use or being built, so cutting during the breeding season, broadly March to August, carries real risk. Write the cutting window into the management plan.

Evidencing retention in the submission

Six items make the retention case, and they should be consistent with each other.

A hedgerow survey giving length, species composition per 30 m section, structure, height, width, gaps and condition, with the sections numbered on a plan. The layout plan showing retained and removed lengths with the metres stated. The construction exclusion zones on a tree and hedge protection plan. The biodiversity metric entries for hedgerow units before and after. A management plan with the manager identified and the regime specified. And the Landscape Strategy showing how new planting connects to the retained network rather than sitting apart from it.

Where a retained hedge runs alongside an ancient woodland edge, the buffer requirements interact, and our note on ancient woodland buffers on a development site covers that overlap.

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