Scrub

Scrub

Scrub is an important part of a diverse farmed landscape; the value of this habitat for wildlife is often underestimated.

Many species rely on scrub for breeding, feeding, basking, roosting and hibernating. Scrub requires some sensitive management to maximise benefits for wildlife and prevent uncontrolled encroachment onto grassland sites.

What

The best scrub habitats have a balance of open areas within scrub, variation in age and structure, and a focus on the importance of the scrub edge which is used by a variety of insects, reptiles and mammals. Where possible scrub should be retained or allowed to develop in areas where this does not affect farming or other valuable habitats.

Turtle dove Streptopelia turtur, adult perched in tree top, Fowlmere RSPB reserve, July 2011

Why

Scrub is an important wildlife habitat, whether it is a few isolated shrubs or young trees, or a dense thicket. It is a natural part of other habitats, such as grassland and woodland, and an important component of the landscape. Scrub is especially significant where little or no woodland exists on site or in the local area.

The blossom of shrubs such as willow, blackthorn and hawthorn is vital for spring insects such as queen bumblebees, solitary bees, hoverflies and butterflies that have overwintered as adults. Within scrub, open areas can support a mixture of rough grassland and tall herb, including nectar and pollen-rich plants such as cow parsley, hogweed, thistles, teasel and knapweeds, which support numerous predatory and pollinating insects.

Structurally diverse scrub can provide cover for a range of wildlife and nesting opportunities for birds. Yellowhammers, linnets and whitethroats favour young, scattered scrub. Dunnocks and willow warblers use low-growing, closed canopy scrub. Turtle doves and song thrushes use older, mature stands of scrub. Nightingales require very dense stands of, for example, blackthorn or brambles.

Scrub is frequently used for refuge and hibernation by amphibians and reptiles. It can provide basking spots for reptiles as well as important over-wintering sites; reptiles often hibernate communally, and some species are site-faithful. Avoiding damage to hibernacula and managing scrub well will help to maintain these important sites for future use.

Scrub that develops along a wood edge is valuable as it creates a transition between woodland and open ground. South-facing edges leading into rough grassland with plenty of sunshine are especially valuable for invertebrates and reptiles.

Scrub can also benefit farms by reducing soil erosion and flooding by reducing run-off. Scrub can also buffer woods and ditches from spray drift and act as a valuable windbreak.

flowering hawthorn - scrub

How

Scrub management for wildlife should create and maintain a range of species, ages and structure through periodic rotational management. Left unmanaged, scrub will develop into woodland.

Creating new areas or extending existing areas of scrub can be achieved through natural regeneration, planting, or simply stopping cultivation or grazing. Larger stands can be created in field corners where two or more hedges intersect.

Where scrub has been neglected, you can increase its structural and species diversity through rotational cutting or grazing. Tall herb and rough grassland creation can be incorporated into rotational scrub management.

Scrub encroachment needs to be prevented where it compromises farming, conservation (for example through shading out species-rich grasslands), landscape or archaeological interests.

Restoration and maintenance of existing scrub

Key features of the best-value scrub include:

  • Sunny, sheltered scrub edges to provide a warm microclimate for insects and reptiles.
  • Scalloped edges increase the length of edge and provide shelter.
  • Sheltered rides through scrub (avoid creating openings that face the prevailing wind or where there are hibernacula present).
  • A patchwork of scrub and glades with diverse vegetation heights.
  • Bramble for nesting and feeding birds, and for insects.
  • Deadwood which supports fungi and invertebrates. You can provide deadwood by leaving dead trees or shrubs standing or by retaining small stacks of cut wood in dappled shade.
  • Bare ground, which is important for insects, reptiles and scarce plants. You can create it if scrub is being uprooted, but avoid areas of archaeological importance and hibernation areas for reptiles.
  • Recently disturbed areas provide bare ground and support food and forage plants for insects e.g. ground-ivy, dead-nettles, ragworts, willowherbs, speedwells.
  • Open areas with tall herbs such as hogweed, cow parsley, thistles, ragworts and teasel. These provide pollen, nectar and overwintering sites for insects, and seeds for birds.
  • Areas of coarse tussocky grassland to provide summer nesting habitat for bumblebees, refuge areas for amphibians and reptiles and winter shelter for many insects.

Cutting scrub

Cutting most species of scrub encourages re-growth, and is useful for maintenance and restoration. Cutting scattered small patches will diversify scrub structure. Plan your cutting programme to take account of existing interests and constraints (archaeology, landscape and species) and to create the desired patch layout.

Cutting should take place between September and February to avoid the bird breeding season, but care must also be taken to avoid disturbing other species including reptiles and amphibians. Cut areas of scrub in a rotation, aiming to retain all ages. Scrub typically matures in 15 years, so cut 1/15th every year or 1/5th every third year, for example. No more than 50% of the area of scrub should be managed in anyone year.

Edge management by mowing or flailing

The rough grassland areas within scrub require mowing to maintain their open nature and encourage flowering herbs. Rotational mowing of less than 50% of the area per year will retain some areas for insects to overwinter. Mow in late summer or autumn after flowers have set seed. If you can, mow in November or December to avoid damage to reptiles.

Planting

Planting should only be necessary where there is no natural source of regeneration or where a rapid result is required. November to March is the best time to plant, ideally using plants of local provenance from locally-collected seeds or bare-rooted whips (nursery-grown saplings).

Planting in rows will create wind tunnels and should be avoided. Instead, scallop the edges of stands, mix species randomly to create diversity or plant in clumps to create a natural appearance. Any unplanted gaps will infill naturally. Try to plant scrub species that create a blossom sequence between March and May (cherry, plum, willows, blackthorn, crab apple, wild pear and hawthorn are a good mix to achieve this).

Shrubs are vulnerable to browsing by livestock, deer and rabbits during establishment. You can protect small numbers of plants with spiral guards or tubes. Larger areas may need fencing to protect them from rabbits and/or deer as required.

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In practice

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