Tree establishment
Having carefully chosen the species of tree and the source of transplants that you are going to use, you must now take equal care over planting and protecting the trees.
The planting of bare-rooted transplants is generally undertaken during the dormant season, normally in late-autumn (only on lowland sites) or early-spring (on lowland or upland sites). Planting of cold-stored transplants (check this with the supplying tree nursery) may be delayed until late spring if conditions earlier in the year are unsuitable.
The following sequence of events will ensure the greatest chance of success if trees are individually protected (click on the links to get detailed procedures):
- Select the locations for individual trees (evenly-spaced? contour-planted?);
- Use a tractor-mounted post-hole borer to cultivate each location to a depth greater than the length of the roots on the bare-rooted transplants. Cultivation at this stage will ensure that each transplant has an adequate rooting depth. If you hit rock or some other obstruction, choose another location;
- Hammer the support post for the shelter or guard firmly as close as possible to the cultivated area;
- Remove livestock (if you haven't already done so);
- Spray each tree location with herbicide;
- Plant the trees;
- Place a tree shelter or net guard over each tree, fix it to the support post, hammer in a light peg on the opposite side and fix the shelter to it;
- Restock with livestock after an appropriate period based on the recommendations of the herbicide manufacturer.
Planting density & pattern | Herbicide treatment | Tree protection | Tree planting | Routine maintenance
Planting at 400 trees per hectare strikes a reasonable balance between the developing canopy size of the trees and the impact of the canopy on pasture production. You can expect up to ten years before pasture production will be reduced at which stage pruning can open up the canopy and prevent further loss of pasture production. On the other hand, with 400 trees per hectare, there are enough trees to spread the effects of the animals, which will use them for shade and shelter, so that no individual tree suffers from severe soil compaction which can reduce tree vigour.
There are many ways in which the planting pattern can be varied to create an interesting landscape.
- Mixed tree species can be planted in the same field, creating a mixture of texture and colour.
- Trees can be planted in the same field in different years, creating a varied age and size structure.
- Trees can be planted in a rigid square pattern with every tree 5 metres from its neighbours. This arrangement makes the use of farm machinery simple but often doesn't "fit" into the landscape.
- Contour planting, in which the trees follow the natural curves of the land, can be a more pleasing pattern but may make driving the tractor and fertiliser spreader more challenging.
- Trees can be planted more densely close to existing woodland, connecting with the woodland and fanning out to lower densities across the field creating the effect of the woodland "spilling" into the grazed field.
- The lengths of the rows of trees, whether straight or curved can be varied so that the planted area has curved rather than straight edges and planting right up to fencelines (especially straight fencelines) should be avoided.
- Planting close to existing mature hedgerow trees should be avoided so that open space is left around them. In any case, the growth of new transplants could be reduced beside mature trees.
These choices offer a great deal of flexibility and the opportunity to create interesting landscapes which follow the land form and which are tied into landscape features.
Within the general pattern, regular, contour or variable density, individual locations which are frequented by the animal should be avoided. Don't plant trees around watering or feeding points or too near gates or on sheep lairs. These areas will suffer from soil compaction, the trees are more likely to receive the attention of the animals and as a consequence, the trees will not perform well on them.
Repeated annual treatment of the spots around the trees with herbicide is recommended for three years after planting. Great care must be taken with these applications of herbicide not to spray any green parts of the trees. Tree shelters which are pressed into the ground can provide adequate protection. If net guards, or net fences with clump planting, are used to protect the trees from browsing animals, a spray shield should be used to ensure that the herbicide spray makes contact only with the pasture species.
If you choose clump planting, you will still need to prepare the ground for planting by treating with herbicide a separate spot for each tree in the clump or by spraying the whole area enclosed for the trees. Spraying can take place before or after the fenced enclosures are erected. It is possible, if the fences are erected before spraying and there is no spray drift outside the enclosure, that livestock need not be removed from the field. Repeated annual applications of herbicide for the first three years after planting are recommended.
Trees may also be planted in clumps. Clump planting involves planting several trees, up to nine, at close spacing within a fenced enclosure. The enclosure for nine trees planted in a 3 x 3 square pattern at 1 metre spacing will be a square of 3 metres x 3 metres. The enclosure will have a standard fence post at each corner and a paling bar around the top supporting sheep net around the enclosure. Using 3 x 3 metre enclosures evenly spaced with 15 metres between their centres, would be equivalent to planting 400 trees per hectare. The cost of this type of protection will vary with the availability of material around the farm and from normal farm suppliers.
You must choose the form of tree protection according to the needs of your site and the cost.
Links to suppliers and distributors of tree protection products are available here.
Tree shelters/net guards: Shelters and guards should be at least 1.2 metres tall for small breeds of sheep (up to 55kg mature live weight) or 1.5 metres tall for larger breeds (55 kg to 80 kg mature live weight) to ensure that the sheep cannot browse emerging shoots. The light stakes normally provided for supporting tree shelters and net guards in conventional woodland are not strong enough to support tree protection in silvopastoral agroforestry. A 3" (8 cm) support post is required for sheep, with an anchor peg which should be 18" (50 cm) long and 1.5" - 2" (4 - 5 cm) square. Hammer the post in as close as possible to the cultivated area so that the tree shelter will fit snugly over the transplant when it is tied to the post. Hammer the stake in (or cut the top off) so that it does not stick out above the top of the shelter (see the upper photo). If you don't do this, there is a risk that when the tree emerges from the shelter it will be damaged by rubbing on the top of the post. The shelter or guard is attached to the stake and the peg by plastic electric-cable ratchet ties. Ties are normally supplied with the shelter or guard; you will have to buy a separate supply of ties for attachment to the peg. You can make your own net guards by buying rolls of suitable plastic net and cutting to size. Netting cut to provide a guard 1.2 metres or 1.5 metres high and 12" - 15" (30 - 37 cm) in diameter will protect the tree from browsing and bark damage for many years (see the lower photo: note the herbicide-treated spot has disappeared). Try to buy rolls of net the width of which is equal to the height of the tree guards you want to make (buy 1.2 metre or 1.5 metre wide rolls). However, if you have to cut the net to the height of the guard be very careful not to leave a ragged edge along the top or use the machine-finished edge at the top. A ragged edge around the top can lead to quite severe damage of the stem of the tree when it emerges form the guard and is moved by the wind. You will need staples or small plastic electric-cable ties to close the netting into a tube shape. Follow the instructions supplied with the shelters or net guards. For example, some shelter manufacturers suggest that you tap on the top of the shelter so that base penetrates the soil and provides protection against voles, for example. |
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Clump planting:
If you choose clump planting, you can erect the fenced enclosure before or after herbicide treatment and before or after tree planting (after tree planting only if livestock are excluded). A square enclosure of 3 metres x 3 metres will protect nine trees planted in a 3 x 3 square pattern at 1 metre spacing. The enclosure will have a standard fence post at each corner and a paling bar around the top supporting sheep net around the enclosure. Using nine trees in a 3 x 3 metre enclosures evenly spaced with 15 metres between their centres, would be equivalent to planting 400 trees per hectare.
Links to suppliers and distributors of tree protection products are available here.
The best practices for handling transplants are contained in the Forestry Commission's Handbook No. 6 Forestry Practice and the Forestry Commission's Bulletin No. 121 Forest tree seedlings.
Tree planting should take place during the dormant period, normally in late-autumn (only on lowland sites) or early-spring (on lowland or upland sites). Trees should be planted after the pasture has been treated with herbicide and after the supporting post for the tree shelter or tree guard has been put in.
The ground should preferably be prepared in advance (see the sequence of events at the top of this page). The use of a tractor-mounted post-hole borer is an ideal way of cultivating the point where a tree is to be planted (and essential for poplar which require deep holes). Use the tractor-mounted post-hole borer to cultivate each location to a depth greater than the length of the roots on the bare-rooted transplants. Cultivation at this stage will ensure that each transplant has an adequate rooting depth. If you hit rock or some other obstruction, choose another location. The loosened soil should be returned to the post hole until the tree is planted to avoid it drying out. When the tree is planted, the roots (or container) should be located well into the cultivated soil, the soil is then "firmed in" in carefully around the tree with the feet to make sure that there can be no movement of the tree.
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If
a tractor-mounted post-hole borer is not available, the trees may be slot-planted
using a spade. The spade is used to cut and open a slot in the turf close
to the supporting post and to a depth which will comfortably accommodate
the transplant's roots. The roots of the bare-rooted transplant are placed
carefully in the slot and the plant carefully "firmed in" with
the feet. The photo shows slot planting in the herbicide-treated spot
beside a support post. Transplants are protected in a bag over the shoulder.Tree planting (poplar cuttings & sets):Poplar cuttings and sets should be planted not later than mid-March in the south of England but may be planted up to mid-April in the south of Scotland (the most northerly latitude recommended for the currently available poplar hybrids).
The soil must be well cultivated so preparation with a tractor-mounted post-hole borer is a good method provided that the hole is deep enough to accomodate the plants and the plants are carefully "firmed in". Slot planting into uncultivated ground is not recommended. Poplar cuttings are inserted vertically by hand into the cultivated area so that the top bud is level with the soil surface. Cuttings must be planted with the buds pointing upwards. Unrooted sets should be planted with approximately one-third of the total length of the set pushed into the ground. The set must be carefully "firmed in" to ensure that no movement of the set is possible, movement will damage the new roots hairs as they grow.
If net guards are used to protect the trees, it is possible for side branches to grow through the net. It has been known for sheep to grab these and pull the tree to the edge of the guard where they can get another bite. It is a good idea to carry a pair of ordinary garden secateurs if net guards are used so that projecting side branches can be trimmed off before they can become a problem. Click for more information on formative pruning. (use the Back button on your browser to get back here)
If, when you walk round the trees after the leading shoots have emerged from the tops of the shelters or guards, you see any forking (double leaders) trim off the weaker or shorter shoot to leave a single stem. Pruning at this stage can be done with a pair of ordinary garden secateurs.
Herbicide treatment should be repeated in the spring of each year for three years after planting to ensure that the trees get a good start.
Check livestock to see if any individuals are particularly attracted to the trees. Individual sheep have been known, very occasionally, to use their front feet to climb up the tree protection so that they can browse emerging shoots. This is more likely to happen with net guards, although tree shelters can be scaled. It is a wise move to shift these individuals to other grazings before the other animals "learn" the same behaviour.