Most new woodlands are planted in former agricultural land, urban fringe areas and reclaimed industrial land, which tend to have few, if any, areas of existing woodland. Those woods or hedgerows that do remain often have an impoverished field-layer flora. This lack of seed sources, together with the poor dispersal mechanisms of woodland plants means that it is nearly impossible for the traditional woodland flora to become established without help.
The field-layer of newly planted woods, especially on former agricultural land which is high in phosphates, typically becomes dominated by aggressive, shade-tolerant species such as nettle, cow parsley, bramble and ivy. These persist for many years and create a further barrier to colonisation by more desirable species.
Introduction of woodland field-layer plants must not be started until the woodland canopy has closed sufficiently that grass and other light-demanding plants have been excluded. Weed control measures which are essential for tree growth in the early years will preclude any introduction of other plants. With close planting of trees, effective weed control and thinning, a 10-year-old plantation should be in a suitable condition for starting introduction of field-layer plants. Light levels beneath the tree canopy should be between 10% and 40% of daylight in summer. Nettles, docks, thistles and other weeds of agricultural land may persist even when light levels are low. If necessary use herbicide or hand clearance to control them before starting the introduction of woodland plants.
Sowing or planting should be targeted in patches which have suitable conditions of shade, lack of competition from other plants and no disturbance from trampling. Suitable areas may only comprise 10% or less of the plantation, but if these can be successfully established, plants will spread into other areas as the conditions become suitable. The aim should be to initiate a self-supporting population of the desired plants, which do not require weeding to survive, and which form part of a balanced, appropriate woodland flora.
Species
Species chosen should be typical of the local area and the type of woodland. Advice should be sought as necessary from local ecologists, the Wildlife Trust or office of English Nature or other nature conservation agency. A similar semi-natural wood within 5km may provide a suitable blueprint, and no plants should be introduced which have not been recorded in the 10 km grid square in which the new wood is situated. It’s best to start with species that are common, and are tolerant of a fairly wide range of light, moisture and pH conditions to ensure reasonable rates of establishment. No attempt should be made to introduce species that are rare in the locality. For lists of ‘desired invaders’ to the new native woodland types, see Creating New Native Woodlands (Rodwell, John and Patterson, Gordon, 1994).
The best way of obtaining plants of local genetic variety is to grow plants from seed collected locally, with permission from the landowner. Only small quantities should be gathered from any one site, and gathering should be done over several years. Some species can be sown direct, while others establish better if propagated and grown on in nursery conditions before planting out. Generally those in the left hand column of Table 7b (below) can be sown, while those in the right hand column should be introduced as plants. Those in the middle column are slow to mature, so planting will speed the establishment of self-sustaining populations. Primroses are best established as plants, at 6-9 plants per square metre. Experience of growing plants from seed is needed for successful nursery production, as wild plants are generally more difficult to propagate than garden plants.
Table 7b: Species groups for introduction of field-layer plants
| Light-demanding, wood-margin and hedgerow species | Species tolerant of deep shade | ||
|---|---|---|---|
| Characteristics | High germination rates; quick to flower; produce plenty of seed | Low germination rates; long seedling phase; slow to reach flowering maturity; produce fair amount of seed | Mainly spread by runners and stolons |
| Introduction method | Sow at low/medium rates; 3kg/ha or 0.3g/m2 | Seed at high rate; 10kg/ha or 1g/m2 | Plant at 4-9 plants/m2 |
| Suitable species | Garlic mustard Lords and ladies False brome Foxglove Giant fescue Hedge bedstraw Wood avens Hairy St John's wort Red campion Betony Hedge woundwort Greater stitchwort Upright hedge parsley | Ramsoms Pignut Wild strawberry Woodruff Bluebell Primrose Sweet violet | Bugle Wood anemone Wood sedge Enchanter's nightshade Wood spurge Ground ivy Yellow archangel Wood sorrel Wood sage Wood speedwell Common dog violet Ferns |
Otherwise, plants or seed should be obtained from nurseries able to supply seeds or plants of local provenance where available. Where not possible, use seeds or plants of British provenance. Advice and lists of nurseries are available at the Flora locale website.
Experience with establishment of woodland flora has shown that it is best to group the species according to whether they are woodland edge plants, or those tolerant of deeper shade, and according to how they spread.
Seed
Seeds should normally be sown in autumn, to ensure cold treatment (vernalisation) which some woodland species require in order to germinate. Sow at the rate recommended by the supplier. Prepare the ground by raking away any recently fallen leaves and lightly rake the soil surface. The seed can be mixed with silver sand or fine sawdust to make it easier to spread evenly. Lightly rake the seed into the soil. Record on a map the areas which have been seeded, so they can be relocated and the success of seeding checked. Where disturbance from the public is unlikely, the seeded areas can be marked with canes or similar.
Plants
Plant in early spring as the soil is warming up but while it is still moist. Plant in single species groups of five or more plants, which should spread to form a stable clump, which can then seed or spread into new areas. Plant at the distances recommended by the supplier. If possible, water the planting holes before planting. Record the location for future reference.
Bulbs and rhizomes
The typical plants of woodland shade are those which grow from bulbs or rhizomes. These allow an early burst of growth, so that flowering and seed production can occur before the canopy closes in late spring. Plants are easy to establish from bulbs or rhizomes, and the establishment time to flowering is shorter than when grown from seed. Bulbs and rhizomes are more expensive than seed.
Bulbs and rhizomes are best planted during the autumn, as soon as they are available from the supplier. Ensure that stock is from British provenance plants, and is produced in a nursery.
Bluebells (Hyacinthoides non-scripta)
Plant 2-3 bulbs in holes 100mm (4”) deep, 600mm (2”) apart
Lesser celandine (Ranunculus ficaria)
Plant 2-3 bulbs in holes 50mm (2”) deep, 150mm (6”) apart
Snowdrops (Galanthus nivalis)
Plant 6 bulbs in holes 50mm (2”) deep, 300mm (1’) apart
Ramsoms (Allium ursinum)
Plant 3-4 bulbs in holes 50mm (2”) deep, 300mm (1’) apart
Wood anemone (Anemone nemorosa)
Plant 2-3 rhizomes, horizontally, 50mm (2”) deep, 300mm (1’) apart
Aftercare
The aim is to establish populations of plants which will spread by seeding or vegetative growth. Nurturing the original plants by weeding in the first season will help the plants to establish, and by reducing competition from other plants, flowering and seeding rates should be improved. The preparation of a suitable seed bed close to established plants may help encourage further regeneration. Wood chips from thinning operations, raked out to leave a layer no thicker than 100mm (4”), rot down to make a good substrate for the germination of woodland plants. In contrast, wood chips have been found not to enhance the spread of woodland edge plants, which are better adapted to seeding into bare soil. Where seed production is prolific, some seed can be gathered by hand and spread in other areas in the woodland.
