How to plant

Note the following general points:

• The roots of bare-root plants must be kept covered at all times, to prevent them drying out. Even a few minutes’ exposure to air can dry the delicate root hairs, reducing the plant’s ability to establish quickly. Keep small bare-root plants completely within a polythene sack until the moment of planting, and keep the roots of larger plants similarly covered.
• Don’t soak or dip bare-root plants in water before you plant. Roots are not able to absorb water this way, and the water may damage the delicate root hairs by washing off the protective soil covering. If plants are delivered with dry roots they should be returned to the supplier. An exception to this rule is when using a root dip, which coats the root hairs with a fine gel that aids establishment.
• Preferably plant on mild, damp days. Avoid days with frost or strong, drying winds.
• Don’t dig planting pits or notches until the day of planting, as they are liable to fill with water. The easiest and most efficient method is to make the pit or notch and plant the tree in one operation.
• On variable ground choose each planting position with care. Keeping to rigid spacing patterns is less important than maximising tree survival. Avoid hollows or dips which may become waterlogged, or patches of ground which are prone to drying out. Don’t plant too close to existing stumps or rocks. On exposed sites, plant in the lee of any mounds or ridges.
• The planting notches or pits must be big enough to take the roots, without having to bend or break any to fit. The main roots stay in the position in which they are put at planting, so take time to ensure they are spread evenly.
• A bare-root tree should be planted to the same depth or slightly deeper as it was growing previously, as shown by the soil mark on the stem. Cell-grown plants are planted slightly lower than previously grown.
• After planting, tread carefully around the stem, taking care not to scrape the bark with your boot. Don’t stamp hard, as this may displace the tree and spoil the soil structure. In clay soils, don’t make a depression around the stem, as this may gather water and result in stem rot.
• Check for firmness by pulling gently on the stem, which should not move. Check again at least once during the four weeks after planting, and firm back in any plants that have worked loose from wind or frost action.
• If at all possible, water the tree immediately after planting, using a bucketful of water per tree, tipped slowly around the stem of the tree so it trickles down into the rooting zone. Such watering aids establishment, and it is worth putting effort into providing a supply of water on the planting day.
• Pit planting should not be used as an alternative to whole-site preparation on heavy clays or other difficult soils (see below).
• Stakes should not be necessary when planting small transplants within woodlands or on other fairly sheltered sites. Some movement in the wind helps develop a strong base to the stem and a good root system. However transplants in very exposed situations may need staking for a year or two, until their root systems are established. Tree shelters and most other tree guards include stakes, which are needed to hold the shelter in position, and so help protect the tree from wind damage. Transplanted standard trees will require staking.

Ground preparation

Tree species should be chosen to suit the location, site and soil, rather than trying to alter site conditions to suit particular species. Planting within or near existing woodlands should follow the local woodland type, which will be adapted to local soil conditions.

Areas available for new woodland planting may be on highly disturbed soils within urban areas, old industrial workings or derelict land, which tend to have poor soil structure and moisture holding capacity. Amenity grassland areas often have soils which are badly compacted from frequent trampling. These sites are often dry in summer, but waterlogged in winter, creating anaerobic conditions which kill tree roots. Pre-planting site preparation to provide at least 500mm of uncompacted, freely draining soil greatly improves tree establishment and long-term stability. On the large scale, this will require ripping or subsoiling using specialist machinery, which can break up the ground beneath grassland without disturbing the turf. For further details see Hodge, Simon J (1985) or Kerr, Gary and Williams, Hugh V (1999). On the small scale, double digging may be needed, as for garden cultivation.

Clay soils

Trees can be difficult to establish on clay soils, which become waterlogged in winter and dry out in summer. Tree roots of most species require air in the soil, and die in waterlogged, anaerobic conditions. Clay soils, although containing plenty of moisture, hold it by strong suction in the minute gaps between the clay particles, making it unavailable to tree roots. Loamy soils, with bigger gaps between the particles, make water more easily available to plants. Where trees establish in a free draining layer over clay soils, they can be very unstable because of the shallow roots. In summer, when the top layer of soil dries out, the tree may suffer from drought because it has no roots into the waterlogged area below. Small cell-grown or notch planted trees tend to dry out in summer as the topsoil dries and cracks. Pit planting is not the answer, as the pit will normally become waterlogged. The only exception are soils which have a ploughpan or impermeable zone in the subsoil, which can be broken up to allow water to drain through. Addition of organic matter may improve the appearance of a clay soil at planting time, but is not necessarily helpful to tree growth (see below).

For large-scale tree planting schemes on clay soils, mechanical cultivation of the whole site will be necessary. For small schemes the following approaches should be considered:

• Reconsider. It may be better not to try planting trees on the site. If the site is damp grassland, it may have ecological value as it is.
• Fence the site against grazing animals, and then natural regeneration of shrubs and trees that are tolerant of the site conditions may eventually appear.

If planting is still required, consider the following options:

• Plant only trees or shrubs that are tolerant of wet sites.
• To increase the range of species which can be grown, improve drainage by digging drainage ditches. The ditches should be aligned to take water slowly off the site. Dig approximately to the dimensions shown, and mound the material in a flattened ridge, starting about 100mm back from the edge of the ditch, so material doesn’t slide back in. The tree should be planted at least one metre from the centre of the ditch.

Soil ameliorants

Research has found that the incorporation of organic amendments into planting pits is rarely beneficial and can be harmful (Hodge, Simon J, 1995). Compost and other organic matter can make the planting pit soil more coarsely textured than the surrounding soil, which can result in waterlogging in the winter and increased drought stress in the summer. Soil ameliorants with high levels of nutrients can damage or ‘scorch’ the roots, when water moves out of the roots under osmotic pressure.

Water retentive gels can be added at planting time. These can absorb many times their own weight in water, which is then available to the plant as needed during dry periods. However if there is a prolonged drought, irrigation will be needed to ‘recharge’ the gel.

Mycorrhiza

Mycorrhiza provide a beneficial association between certain soil fungi and the roots of trees and other plants, through which the fungus supplies dissolved nutrients and water to the tree. Mycorrhizal associations are vital to woodland ecosystems. Mycorrhizal activity can be encouraged at planting by the use of root dips or powders which contain mycorrhizal spores. For suppliers see here.

Alternatively, the introduction of rotted leaf mould from around an existing nearby tree of the same species is thought to help initiate mycorrhizal associations. Rake away the top 25cm (1”) layer of leaf litter from an area of about two square metres, and then carefully scrape away the top centimetre or so of organic material, taking care not to damage any surface roots. Add about half a spade of this material into the planting notch or hole.

Planting in grass

When planting in a grass sward, for example planting a new woodland on a former pasture, it’s best to leave the grass sward undisturbed, and then use mulches or herbicide after planting to create a grass-free zone around each tree. If the whole sward is ploughed or treated with herbicide before planting, there is likely to be strong growth of weeds. These are much more difficult to manage than the grass they replaced.

Planting notches or pits are relatively easy to make in short turf thathas been regularly grazed or mown, but more difficult through a thick thatch of long grass. Consider mowing the planting area a few times in the months prior to planting, as this will make it easier to dig notches or pits, and herbicides or plastic sheet mulches are also more effective on newly-grown short grass.

If making a notch through grass is too difficult, you may need to remove a few turves first and then plant into the bare ground. Removing a few turves will also be necessary if you want to make a planting pit. The turves can either be broken up and discarded, or turned over around the planted tree.

In damp ground, cut a thick turf, preferably about 230mm (9”) thick, and turn it over to create a better drained planting position. Make a slit through the turf and plant the tree. Inverted turves are not effective in controlling weeds, and herbicides or mulches will be needed.

If you don’t plan to use either a herbicide or a plastic mulch to control weeds, you will need to start with a generous weed-free area, and maintain it by hand weeding or hoeing. An area with sides equivalent to four spades’ width is not too big, though it will seem so when you plant. You must weed regularly, or by mid-summer the planting square will be grown over with weeds, adversely affecting tree growth. This method of weed control is labour intensive, and it is easy to damage the tree stem or roots with a hoe or fork.

Ploughed or ripped ground

Where soils have been ploughed to reduce compaction, ridges will be formed. Planting along the ridges will be beneficial in providing a better drained planting position, as shown above. On exposed sites, plant on the leeward side of the ridge, to give some shelter.

Where compacted ground has been loosened by ripping or subsoiling, it’s not advisable to plant along the rip line, as this will tend to open up in dry weather, exposing the tree roots. Plant between the lines instead, using either notch or pit planting.

Planting in existing woodlands

Ground preparation will not normally be needed for planting within existing woodlands, as soils will be suitable for tree growth. Planting may be needed because of lack of natural regeneration, or to improve age or species diversity. However note the following:

• Following tree felling, either for clearance or harvesting purposes, soils tend to become wet because of damage to the soil structure during extraction, and because of the sudden loss of transpiration due to tree loss. Temporary drainage ditches may be needed to take water off the site. Plant on mounds or any dry patches within the cleared area.
• The absence of trees at a particular place within a woodland may indicate that the soils are unsuitable, and it may be best to leave the site unplanted.
• When replanting a recently cleared area, plant in the gaps between the stumps, rather than close to them. If the stumps are being left to regrow, they will soon outgrow any tree planted nearby. Planting close to rotting conifer stumps or treated broadleaved stumps may increase the risk of fungal damage.

Notch planting

Notch planting is generally the best method of planting young bare-root trees, which are in turn the best size of plant for rapid establishment. Roots of vigorous young trees are very strong and will have no difficulty penetrating normal soils, provided they are not competing with grass for water and nutrients. Notch planting reduces the effects of windblow because the transplant is held firmly in the notch, which is made with minimal ground disturbance. This lessens the requirement for staking. However if notch planting is badly done, with roots crammed into too small a space, or notches not properly closed, losses will result. Young trees with spreading roots will need to be pit planted, and trees should not be notch planted direct into clay soils without previous soil preparation. Trees notch planted into recently cultivated ground should be planted so that the soil mark on the root collar is about 2-3 cm below ground level, to allow for soil settlement. Similarly plants on newly made mounds should be planted a little deeper than normal. This is to avoid the possibility of plant roots becoming exposed through soil settlement or erosion.

Use a heavy, straight-bladed spade or specialist planting spade to make the notch, which should be just deep enough to take the roots. Push the blade into the ground, and then move it backwards and forwards to open up a notch. With a sideways, wiping motion, slide the plant into the notch and pull it upwards to spread the roots. Tread carefully but firmly around the stem to close the notch and prevent any movement in the wind.

For plants with larger root systems, make two cuts in a ‘T’shape as shown, to open up a larger notch to take the roots.

Cell-grown stock

Note the following:

• Cell-grown plants can be planted with an ordinary spade or trowel, but a special tool called a ‘spear’ makes planting easier and quicker.
• The top of the cell or plug must be at least 12mm (half an inch) below the soil surface, and covered with soil. It left exposed, the compost in the cell dries out and does not easily re-wet.
• In heavy clays, cell-grown plants should not be planted without earlier ground preparation.
• Plant boxes and carriers are available from suppliers of cell-grown plants, for use during planting operations.

Pit planting

Pit planting involves digging out a pit, large enough to take the roots, and piling up the soil temporarily at the edge of the pit. The tree is then planted and the hole backfilled. Pit planting is required in the following cases.

• For transplants or other young trees which have roots that are too bushy and spreading to fit in a notch.
• For container-grown plants other than cell-grown plants. These might include holly or other evergreens which do not survive bare-root transplanting, and are grown for two years or more in containers.
• On sites with disturbed soils that have not been prepared by machine cultivation. On steep slopes, stony ground or other difficult sites young trees will normally benefit from pit planting. However pit planting should not be used instead of whole site preparation on clay soils or those prone to waterlogging (see below).
• For standard trees which have large root-balls or are grown in large containers. Standard trees have a poor success rate, and are not recommended for planting, other than for orchards or gardens.

Pit planting has the advantage over notch planting in that it makes it easier to plant the tree without damaging the roots, and breaks up the soil to allow the roots to spread. The main disadvantage is that it takes longer. For small transplants planted into cultivated ground, there is no evidence that pit planting improves establishment, and notch planting is the standard method used for large-scale woodland planting.

Some people find that a ‘hybrid’ method works well, combining the advantages of digging a pit with the speed of notch planting. This is also a good system for pair working. One person cuts through the turf and digs out a sod of earth which is kept on the spade, resting on the ground by the hole. The other person places the tree in position and spreads the roots, and then the first crumbles the soil back into the hole. With experience, one person can do this on their own, by tipping the soil gently off the spade whilst holding the tree with the other hand.

When pit planting bare-root stock it is not necessary to add compost or other organic matter. Additional organic matter can be helpful in establishing container-grown stock (see below).

Procedure

To pit plant a tree:

1. When planting in grass, first remove some turves. If herbicide or mulch is going to be used for weed-control, you need only remove sufficient turves to dig the hole. To create a clear metre square for hand-weeding, remove eight turves. The turves can be inverted around the pit, chopped up in the bottom of the pit, or inverted around the tree.
2. Dig a pit large enough to take the roots or root-ball, and put the soil to one side. If there is a difference in the top and lower layer of soil, pile up separately. Dig the hole square rather than round, as round holes encourage roots to spiral.
   
3. In cohesive soils, loosen the soil in the sides and bottom of the pit with a spade or fork.
4. Place the tree centrally in the pit, checking that the soil collar is at the correct height, and spread the roots. If working as a pair, one person can hold the tree while the other backfills carefully around the roots, using the friable top soil first. Shake the tree gently so that soil trickles down between the roots. Backfill with the rest of the soil, finishing with the subsoil.
5. Tread gently around the tree to firm the soil, taking care not to scrape the bark of the tree with your foot.
6. Water the tree if possible.

Container-grown stock

Nearly all native trees for woodland planting are supplied bare-root or cell-grown, but holly and a few introduced species such as holm oak are supplied container-grown, in peat, coir or other light, friable composts. This is because they are slow-growing evergreens, and are too small to plant out as one-year-old cell-grown seedlings, and do not transplant well bare-root. After planting, the roots may not easily make the transition into the surrounding soil, especially if there is any spiralling of roots within the rootball. Adding compost, leaf mould or other organic material when backfilling the planting pit should encourage the roots to grow out of the rootball and into the surrounding soil.

Before planting, make sure that the compost in the container is moist throughout, as if planted dry, it will tend to stay dry. If a rootball of peat compost has been allowed to dry out before planting, re-wet it with a solution of about 5ml of washing-up liquid in 5 litres of water.

Follow the general procedure given above for pit planting, but mixing in the compost and soil when backfilling. Plant so that the surface of the compost can be covered with a thin layer of soil. If the compost is exposed at the surface, the water tends to evaporate more quickly from the compost, leaving the rootball drier than the surrounding soil.

Staking

Small transplants (eg 40-60cm) do not require staking to prevent displacement by the wind, as correct notch-planting techniques should hold them firmly in the ground. Tree shelters and other tree protection products are widely used with transplants, and protect against wind damage as well as browsing. More details on tree protection are given below.

Stakes may be needed for taller transplants (90-120cm) in exposed positions, or where it is considered that stakes may help prevent accidental damage or vandalism. The Conservation Volunteers can supply square stakes in a range of sizes from 75 cm to 1.5m height, and 50-75mm diameter round stakes 1.65m height.

Procedure

It is easier and safer to knock in the stake after you have planted the tree, to avoid the chance of the stake causing injury to the face when you bend down to plant. The stake should normally be put in on the south-west side of the tree, so that the prevailing wind blows the tree away from the stake. When planting, avoid placing any spreading roots at this point, or they will be damaged when the stake is knocked in.

Plant the tree by notch planting or using the ‘hybrid’ method described above. Place the stake on the south-west side of the tree, and knock it in until it is completely firm in the ground, and no higher than one-third of the tree height. As explained below, it is important that the upper part of the tree sways in the wind, to encourage strong roots and lower stem diameter. Any excess height should be sawn off, as the stem may chafe against it. Attach a tree tie at the one-third height.

Where stakes are functioning mainly as markers to make trees easy to locate in nettles, bracken or other tall vegetation, it is much cheaper to use bamboo canes. Proper weed control measures should ensure that trees are not lost in vegetation.

Sturdy round diameter tree stakes have the useful incidental function of protecting tree trunks from mower damage, which is a frequent cause of damage to young trees near mown grass. It’s worth ‘staking’ any vulnerable young trees alongside mown paths or on the outer edge of any tree planting area surrounded by mown grass. In this case ignore advice about prevailing wind, and instead put the stake where it will protect against prevailing mower damage! Retain stakes in this position for as long as mower damage remains a possibility.

Pit planted trees

Larger, pit planted trees, for which tree shelters are not appropriate, will normally require staking. This will include pit-planted young trees over about 1.5m (5’) tall, or 1.2m (4’) tall if planted in exposed positions. The function of the stake is to hold the base of the stem firmly and allow the roots to establish, but not to prevent wind sway. Research has shown that it is the swaying of the tree in the wind which stimulates the growth of the stem diameter. If the tree is staked and tied just below the crown, the stem cannot sway, and little increase in stem diameter occurs from base to crown. In extreme cases the stem may become thicker above the tie than below it. Wind sway also stimulates the growth of roots at the root collar.

Stakes and ties cost money and need maintenance to check they are not rubbing or restricting stem diameter growth. It is much better to avoid the need for them altogether by planting younger, smaller trees.

Remedial staking

Sometimes young trees become displaced by exceptionally strong winds, or where temporary flooding has caused root damage. A short stake or stakes should be used to secure the tree until root growth has recovered. Knock the stake in on the windward side of the tree, and attach the tie at a point no higher than one-third the height of the tree. Use a proprietary tree tie, which has a spacer between the tree and stake or is tied in a figure of eight, to prevent chafing. Most ties will need nailing to the stake to stop them slipping. On buckle ties, the buckle should be at the stake, not the tree stem. Double stakes can be used as shown.

A stake should only be required for two growing seasons, by which time the tree should have put on sufficient root growth to hold it firmly. If it hasn’t, improved weed control measures should be used to encourage the tree into growth.