Scrub Communities
Scrub communities are associations of shrubby plants that are woody-stemmed but which don't reach full tree height. Scrub can develop on a range of different sites and may be the result of poor, shallow or dry soils that prevent the full development of woodland. Scrub can also develop as a successional habitat between open plant communities such as grassland, and woodland.
Since scrub communities tend to consist of multi-stemmed woody plants without a clear trunk, there is significant shading of the groundlayer, so associated plants tend to be those that form in the spaces between the bushes. Such communities tend to be made up of coarser, taller grasses and perennial herbaceous plants that grow amongst them.
1. Mixed Scrub
Species-rich communities of scrub often form on thinner, chalky soils and can be a feature particularly of Breckland and the chalky soils around Newmarket and South-east Cambridgeshire. Members of the rose family are strongly represented and can include Common Hawthorn, Blackthorn, European Crab Apple, Common Dog Rose and others. On chalky soils, Wayfaring-tree and European Buckthorn can be frequent, too. Elsewhere, European Privet can be frequent, while European Elder is a major constituent of any scrub that develops on disturbed ground such as on brownfield sites, on abandoned or little-used ground (such as around old farm buildings and derelict sites) and similar places. On wet ground, scrub can often consist of large stands of Blackthorn, but Guelder-rose, Alder Buckthorn, European Elder and Common Hawthorn can also occur. Forms of mixed scrub are frequent in coastal locations, where harsher growing conditions prevent the formation of woodland communities. Such communities typically have similar species to those found in inland communities but some can have a single dominant species, such as in thickets of Sea-buckthorn.
Scrub has often been treated as a plant community associated with abandoned land and, as such has sometimes been ignored as a major habitat type, even by the conservation organisations. However, these bushy communities have traditionally been important habitats for a whole suite of birds that are disappearing, in part because of the loss of scrub through a general 'tidying up' of the countryside. Species such as Eurasian Turtle Dove, Common Cuckoo, Garden Warbler, Common Nightingale and others are all reliant on scrub habitats and all in decline.
Groundlayer species associated with scrub include taller grass such as False Oat-grass, Rough meadow-grass and Cock's-foot and a range of non-native and native, herbaceous biennials and perennials, such as Red Campion, Green Alkanet, Foxglove, Creeping Cinquefoil, Ground-ivy and Cow Parsley.
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| A species-rich, mixed scrub community with a good range of shrub species and species-rich, chalk grassland. Habitats such as this are generally maintained by sympathetic grazing and can be exciting places to look for plants. | A mixed scrub community developed on abandoned ground and dominated by suckering stands of Blackthorn. |
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| Hawthorn-dominated scrub and species-rich grassland on old workings at Barnack. Again, sympathetic grazing maintains the habitat and prevents any possible succession to a tree community, though the shallow soil probably also reduces plant growth. | A Silver Birch-dominated, mixed scrub community on an old gravel extraction site. Other species include Common Gorse, brambles and Common Broom. |
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| Scrub communities are important habitats for some of our rarer small trees and shrubs. European Crab Apple has largely disappeared from our region, probably most through introgression with introduced Cultivated Apples. But some fine specimens can still be found in the wilder parts of Breckland. |
| Some Typical Species
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Species to Look Out For
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Places to Visit
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2. Hedgerows
Hedgerows form the structure of much of our countryside across large tracts of arable farmland. They are essentially very long and very narrow strips of scrub and tend to have similar plant communities to those of scrub habitats. Although some hedge lines may come about by the reduction of existing scrub, most hedges were originally planted and, as such, their shrub content is purely artifical. Old hedges that have remained for perhaps several hundred years, tend to contain more species, both in their shrub content and in their associated groundlayer. More recently, single-species hedges were widely planted - most often of Common Hawthorn) and for a time it was held that counting the number of shrub species in a 30-yard length of hedgeline and multiplying the number by 100 would give you an approximation of the hedge's age (known as Hooper's Rule). However, more recently still, there has been a trend to plant far more diverse hedges, so Hooper's Rule only still works so long as you visually assess the hedge to be more than 30 years or so old before you start.
Since most hedges tend to surround arable fields, the vast majority have little in the way of an associated groundlayer, due to mechanical cultivations and drift from herbicide spraying. Near the coast, an increasing number of hedges have little more than an aggressive strip of introduced Alexanders at their base.
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| Lines of Common Hawthorn and Blackthorn hedgerows, with occasional Pedunculate Oaks and regenerating Smooth-leaved Elms, break up arable landscapes throughout much of the East Anglian countryside. |
Blackthorn flowers en masse in April, following on from an equally impressive showing from Cherry Plum in late March. |
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| Hedges that are allowed space can be as productive as areas of mixed scrub and include a good range of species, such as this Guelder-rose. | Many species of scrub and hedgerow habitats present their seeds in fleshy fruits, especially members of the rose family. This makes them important habitats for birds and small mammals. |
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| Traditional hedge management, known as hedge-laying was a fine art in years gone by, but few retain the skills these days. Good management of hedges is essential if a species-rich community is to develop and if the hedge is to fulfill its purpose as a shelterbelt and windbreak. |
Present-day hedge management is carried out with tractor-driven, mechanical flails. Sadly the rough cuts take longer to heal, causing a delay in hedge recovery and leaving the plants open to infection. The majority of hedgerows in our countryside are in decline. |
3. Gorse Scrub
This is a particular type of scrub that develops on dry, acid soils and is most often associated with heathland. The community consists predominantly of tall, dense bushes of Common Gorse but can also include smaller quantities of other woody species normally associated with acid heath, such as emergent Silver Birch and Common Rowan and scrubby Common Hawthorn, Blackthorn, bramble and Bracken. Such communities were probably kept in check in the past by regular grazing/browsing by livestock, but these days, it's more often mechanical cutting that is used on a periodic basis.
Because of the dense nature of the scrub, there is typically little or no groundlayer and associates tend to be remnants of former heathland communities that survive for a time until overwhelmed. If birch growth is dense enough, the gorse can become supressed and an Oak-Birch woodland community can develop.
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| Common Gorse and Silver Birch encroaching on an area of unmanaged heathland. |
| Some Typical Species
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Species to Look Out For
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Places to Visit
of the region, but most commonly on the acidic soils of the mid-Norfolk Heaths, North Norfolk, and Suffolk Sandlings. |
4. Bracken Stands
Common Bracken is an unusual fern in that it spreads to form extensive colonies from a creeping, rhizomatous root system, with the leaves arising afresh each spring and rising individually on long stems directly from the ground. The leaves are broad and densely populate the ground and this, together with the thick mat of dead material that builds up from previous year' decaying leaves, creates a mono-species habitat that few other plants can become established in.
Bracken grows extensively on a range of different soils, but is most successful on dry, acidic soils and forms its largest colonies on heathland and coastal, sandy soils. Any associated plant species are most likely to be relics of previous plant communities, especially where the Bracken cover is newly colonising, but a few plants may regularly be found amongst its fronds, including Common Foxglove and Creeping Corydalis.
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| Bracken can form a dense understorey to some woodland communities on acid soils, especially Oak-Birch woodland and Pine plantations, but it can become a dominant community on more open ground, especially after forestry clear-felling. |
A view under the canopy of Bracken leaves reveals the density of the leaf cover and of the ground litter from dead plant material. |
| Some Typical Species
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Species to Look Out For
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Places to Visit
of the region, but most commonly on the acidic soils of the mid-Norfolk Heaths, North Norfolk, and Suffolk Sandlings. |