Management of woodlands and hedgerows
Established mature woodland that has been under-sown with a woodland seed mixture may require little management during establishment. Establishment in woodland where light levels fall below 50% of that in the open is slow by comparison with sowing seed in the open. Some species, for example bluebell, take several seasons to germinate and 4-6 years to reach flowering.
Open or young woodland
Open or young woodland with higher light levels will produce more growth and grasses will be more prominent. In these conditions an annual cut mid-summer may be worthwhile for a more managed appearance and to keep weeds of semi-shade like nettles and brambles in check.
New tree plantings
These will take 10-15 years of tree growth for the canopy to close and for light levels to drop. During this initial phase seed mixtures that have been sown should be managed as grassland. As ground cover declines and shade increases to 50% woodland plants will have more opportunity to thrive. This is a good point at which to sow additional woodland wild flower seeds.
Longer term woodland management for ground flora
In the long term, ground flora will benefit from woodland management which maintains a patchwork of different habitats; with light levels which vary from deep shade to dappled shade to temporary open glades; and with patchy ground conditions including bare soil, mosses and leaf litter.
Many wild flowers will struggle to survive in very deep continuous shade and depend on occasional tree death or woodland management such as coppicing or thinning to introduce light for their regeneration. Younger plantations with even-age stands of trees in particular can enter a uniformly dark phase after canopy closure; this will suppress ground flora diversity unless managed. A staggered programme of coppicing or thinning of trees and shrubs to open up temporary patches or glades will over time develop an ideal mosaic of areas in transition from light to deep shade which will encourage woodland floral diversity as well as associated insects, birds and other wildlife.
Weeds in woodland
The most troublesome ‘weeds' in woodland are nettles, cleavers, cow parsley and brambles. These weeds being only partially tolerant of shade are usually more prominent in woodland edges and glades. Chemical weed control is not really an option in woodland, and is not effective for these species anyway. Woodland management which increases shade levels (e.g. dense planting including under-storey shrubs), will help weaken these plants. Low numbers of weeds can be successfully removed by digging them out. Mowing in more open situations can help keep these weeds in check. Woodland ‘weeds' tend to be associated with more fertile sites and as with grassland schemes heavy infestations of nettles or cleavers indicate fertility levels which mean that weed problems are quite persistent and diverse results difficult to maintain.
The wildlife habitat value of woodland is further enhanced by permanent open rides, glades and margins with structurally diverse shrubby edges. These can be managed as in the following section.
Hedgerow, Glade and Margin aftercare
Hedgerows, woodland edges, rides, glades and other semi-shaded communities usually sit on the boundary between one habitat type and another; for example at the transition zone from open grassland to closed woodland. The management requirements of established hedgerow mixtures can be tailored to light levels and to fit in with adjacent vegetation types.
First year management
In the first year after sowing a seed mixture annual weed growth should be cut back regularly. This will encourage the development of a good perennial ground cover and will to help control problem hedgerow weeds like cleavers and sterile brome. Residual perennial weeds such as docks can be dealt with by spot treatment see weeds for more on this.
Management once established
Zoned management of hedgerow and woodland margins frequently produces the best diversity of habitat structure. Areas closest to the hedge or woodland boundary can be left uncut in most years. Areas that are further from the margin and more open can be managed as grassland habitat. For example in a 6 metre sown margin the 2-3 metres against the boundary should be left uncut, the next 3-4 metres cut once or twice a year.
Hedgerow vegetation that is not mown or grazed each year will become rough and "tussocky" in character over time. This can form useful refuge habitat on corners and margins of a site.
To control scrub and bramble development these tussocky areas may need cutting every 2-3 years between October and February. For wildlife this cutting is best done on a rotational basis so that no more than half the area is cut in any one year, leaving part as an undisturbed refuge. Mowing established tussocky vegetation may require heavy duty cutting equipment: domestic mowers would not be tough enough to deal with the thick tussocks or woody scrub that develops.
Hedgerows, glades, rides and margins that are cut each year can be managed as grassland.