Basic rules for tree establishment

These apply to almost all situations, and for any numbers of trees, from small groups to new woodlands.

Size of planting stock

Plant small. Young trees for planting are referred to as either tree seedlings, transplants or undercuts, depending on how they’ve been grown, and are usually 30-60cm high. A ‘whip’ is any of these, with a single leading stem pruned of side growth, whereas a ‘feather ’ has several side shoots. Young trees have many advantages over larger stock. They establish quickly, and in a few growing seasons, catch up or overtake trees planted as standards. Young trees do not need stakes to hold them firm, and develop a strong anchorage of roots as they grow. Trees planted as standards (1.7-1.8m tall) and then staked tend to produce less vigorous root systems, which are unable to support them when the stakes are removed. Standards need watering during dry spells for at least the first season, whereas smaller plants with a better ratio of roots to shoots can flourish through droughts without watering. Small trees are less prone to vandalism, because they are less noticeable, and less inviting to pull over and break. If they are damaged, the loss is minor as they usually regrow. Seedlings or transplants (see below) are very much cheaper than standards. Where people want to plant standards for ‘instant’ results, or because they think this is a short-cut to creating a parkland landscape, they must be persuaded otherwise!

Native trees are available from tree nurseries in the sizes given below. Larger sizes may also be available, but are not recommended for the reasons given above. 1 year trees are seedlings that have not been transplanted. Transplanted trees produce a better ratio of roots to shoots than do non- transplanted trees, and establish better when moved to their final planting position. ‘1 u 1’ indicates that a one year old seedling has been undercut with a spade, to stimulate fibrous root growth, and then grown on for another year in the same position. Some nurseries may also supply trees grown in containers. native evergreens such as holly and juniper do not transplant well as bare root plants. Other plants may be pot-grown to allow planting at any time of year. Pot-grown plants are more expensive than plants supplied bare-root.

Spacing

Trees and shrubs for small copses or woodlands should be planted at close spacings, of about 2m, and then later thinned. Even for intended groups of three or four trees, it is more effective to plant 30-40 whips, and then thin out at about 5 years and again at 10 years to retain the trees you want. Mass planting allows for losses, and creates a sheltered shrubby habitat which mutually benefits the young trees. The whole area can be fenced, or the vegetation allowed to grow up around the plots of trees so they are less likely to be trampled. Vary the spacing to avoid planting in rows, leave plenty of space for rides and glades and choose mixtures of trees and shrubs which suit the local conditions and the type of woodland you want to create.

Unless the failure rate has been very high, thinning is essential to avoid creating a dense, shaded wood of spindly trees and straggling shrubs with little ground flora.

From the ‘thicket stage’, at 5-10 years, thinning can be used to develop a range of woodland types. Depending on the species used, these types may vary from a forest of tall trees with a closed canopy, a wood with all the woodland layers, through to individual trees in grassland.

It is important that the local community are informed and consulted about management of the developing wood, to avoid misunderstandings. In particular, the thicket stage can be seen as ‘scrubby and overgrown’. Conversely, any thinning may be viewed as destructive. In the short term thinning will cause losses to wildlife, but in the longer term is essential to create an attractive, valuable and useful habitat. Thinnings can be chipped for mulch to be used either within the wood or elsewhere, or used for garden poles, firewood or other uses.

Soil

Topsoil is not necessary even on sites with stony substrates. Topsoil can be a hindrance because it encourages lush weed growth which competes with the trees. Imported topsoil will bring in unwanted weed species, and make it more difficult to encourage the development of a woodland flora. Even on very altered substrates, it is usually better to work with the existing conditions, and make the most of any natural regeneration of trees and other plants, non-natives included.

It is not necessary when planting whips to dig a planting hole and fill it with topsoil. Planting holes tend to become either waterlogged in poorly drained soils, or dry out in stony soils, and even if tree root growth within the planting hole is good, it may not root into the surrounding subsoil. Fertiliser may be necessary in some situations to help new trees establish, or to accelerate natural regeneration. Fertiliser application must be accompanied by effective weed control, or the fertiliser may be counter-productive by merely encouraging growth of weeds, which are able to take up the fertiliser more quickly than the trees can. Areas of disturbed ground, industrial sites, and those that are supporting little vegetation even after some years will need checking before planting. Soils should be analysed for phosphorus, potassium and magnesium, and soil pits dug 700mm deep to check for drainage and compaction. Badly compacted soils will need ripping to improve drainage. For further information see Creating and managing Woodlands around Towns, Forestry Commission (1995).

Weed control and conservation of soil moisture

Weed control for the first three to five years is essential. An area of at least one metre diameter around each tree should be kept free of weeds. This can be done with herbicide, mulches of various types or by hand weeding.

Weeds interfere physically with tree growth, and compete for soil moisture and nutrients. Most soil moisture is lost by transpiration from leaves, with smaller losses from bare soil. If these losses can be reduced, there will be more soil moisture available for the young trees. nutrients only become available when the soil is damp.

The worst surround to a young tree is mown grass, which effectively sucks the water out of the ground. The best is to start with damp, weed free ground, which is then covered with a mulch. The difference between the two in tree survival and growth is startling.

In general, herbicides are most effective for the ‘spot treatment’ of a one metre diameter area around a tree. Mulch covering one square metre is less effective, as weeds root in from the sides. If a larger area can be mulched, this becomes more effective than using a herbicide.

Herbicides

The herbicide propyzamide is a pre-emergent herbicide, which can be applied immediately after the trees have been planted, but is only effective on bare soil. It should be applied before the end of January in warmer districts, and before the end of February in the north and east of the Uk. Propyzamide in the formulation kerb Granules is approved for amateur use. When planting into turf, the most effective herbicide is glyphosate, available through garden centres and other retail outlets under various trade names. Glyphosate can be applied by hand spray on unwanted vegetation any time during the growing season. It is most effective when used at the time of maximum growth of the weed plant, but before it flowers. Follow manufacturer ’s instructions when using herbicides.

No-one under 16 years should apply herbicides. Professional herbicides from agricultural suppliers, or any herbicides used in return for payment to the group or an individual must only be applied by trained and qualified persons.

Mulch

Any material which suppresses weed growth, so retaining soil moisture, can be used as a mulch. Various mulch mats are available from tree planting suppliers, which are ready-cut with a slot for easy fitting around the tree. Alternatively, mats can be made out of thick dark plastic, carpet, underlay, linoleum or any other sheet material. On free draining soils, cover as much of the tree planting area as possible for the best results. A black plastic sheet, for example 10 x 8m and mulching 40 trees at 2m spacing, will result in very fast tree growth. Lack of direct rainfall appears not to be a problem, due to sideways movement of soil water. On damp soils, total coverage may cause waterlogging beneath the mat which is detrimental to the trees. When the material is removed, the weed-free ground beneath is ideal for establishing a woodland flora. Flexible material should be anchored around the edge with pegs, stones or soil. Covering sheet material with stones, gravel or bark will anchor and disguise it, as well as discouraging voles from gaining access to the tree stems from beneath the sheet. Sheet material designed specifically for mulching should not fade or become brittle in sunlight, but other materials probably will, and a covering will protect it. Non-biodegradable sheet materials should be removed after about three years.

Loose material which can be used as a mulch includes wood chippings, coarse compost, composted bark, rotted manure, stones and rubble. A layer at least 75mm deep should be used.

See Trees and Weeds, Forestry Commission (1987) for details.

Protection

Young trees may be vulnerable to damage by rabbits, voles, squirrels, deer, grazing stock and vandals. In urban areas it is generally best to use as little protection as possible, to avoid drawing attention to the trees. Fencing, tree shelters and spiral guards all attract attention and vandalism. Where rabbits are a problem, use spiral guards fitted to the trees. Where vole damage occurs, use herbicides rather than sheet mulches for weed control. Voles use the cover of sheet material or tall grasses to reach the tree stems. Only ring-fence the planted areas when it is necessary to keep out horses or other grazing stock. However, it is not unknown for horse-owners then to break through the fences in order to take advantage of the grazing within! Deer damage is unlikely to cause significant losses in most urban areas.

Squirrels can damage or kill established trees by stripping the bark, especially of smooth-barked trees such as beech and sycamore. Trees are most vulnerable when about 16m top height (10-40 years). It may be advisable to avoid planting these species on sites where squirrels are numerous. Cherry, lime and ash are less susceptible to damage.

How to plant

The young trees should be supplied from the nursery in special sealed plastic sacks which are white on the outside and black on the inside, to prevent the roots from drying or warming. If the trees can’t be planted straight away, they can be stored as they are in a cool dark building for two or three weeks. Handle and store the sacks carefully to avoid bruising the roots. If there is no suitable indoor storage, the trees should be taken out of the sacks and placed in a shallow trench with the roots covered with soil. Transfer of bare-root stock from bag to trench, from bag to bag or during final planting must be done carefully but speedily, so that roots never for a second become dry. Any drying will reduce their chance of successful establishment.

Do not plant when there is a ground frost or in very cold winds. Preferably choose a still, misty, damp day when drying of the roots will be minimised. When you are ready to plant, transfer the trees quickly from the sealed bags to special planting satchels or clean plastic sacks. Do not use unwashed fertiliser sacks as the residue may damage the roots.

To plant, make a notch in the shape of an L, H or T, and lift the turf forward with the spade. Plant the tree by gently pushing it down into the notch, and then withdrawing it slightly to spread the roots. The existing soil mark on the root collar indicates the correct planting depth. Firm the turf down with the foot.