Ideally soil preparation should be carried out well ahead of planting. Preparation could include incorporating organic matter into the soil to improve aeration and assist drainage of compacted soils, and to improve soil nutrient holding capacity. Specific preparation may be needed if the soil has an inappropriate pH or is lacking in certain elements. Similarly, contaminated soil or soil containing excesses of some elements will require amelioration prior to planting. Trees with a limited soil tolerance range may require very specific soil preparation to enable their requirements to be met.

Where drainage is a serious problem, particularly in built environments, laying drainage pipes may be necessary before planting takes place.

The greater the area prepared for planting (soil volume) the better; tree roots will become established and continue to grow healthily in a good medium. Soil preparation is especially important with compacted soils.

Soils that have a distinct clay sub-soil should be treated cautiously - especially if the soil profile does not have the depth to plant the tree in the existing topsoil. It is very important to not disturb or dig into the clay sub-soil unless it is free draining, and in most situations it is not.
If topsoil is shallow, say less than 400mm, soil level will need to be built up to allow sufficient soil volume for newly planted trees to establish well in.

If importing soil on to the site, its performance will need to be monitored over a growing season, keeping in mind that most imported soils are poor in nutrients as well as being a source of weed seeds. It is better to incorporate compost through the soil to build up its profile rather than import soils.

In situations where the entire soil surface level cannot be raised, soil will have to be mounded around the trees individually so that they are not planted into the clay sub-soil. Once again the greater the soil volume the greater the chance the tree has to establish quickly and
grow strongly.

A common mistake made is to dig down into the clay sub-soil and replace this with 'good' soil; this will result in creating a sump which may collect water or at least produce a planting profile with poor drainage and provide low levels of soil oxygen. Once the site has been properly prepared the tree planting can begin.

Dig a hole that is wider than, and to the same depth as, the root ball of the tree. Make sure the base of the hole is firm as the tree will sink when watered in.

Planting method will depend on the type of container the tree has been grown in. Trees in 'air pruning' containers or in pots need to have the pot removed and any roots which are spiraling or matted at the base of the root ball need to be pruned. Trees in Root Control Bags (RCBs) need to be taken out of the RCB. Bare root trees may need a light prune to remove any damaged roots or excessively long ones.

Fig.1 Bare Root Trees. The hole should be large enough to adequately fit the root ball in. It is better not to prune to fit since the roots have already been pruned once and this will cause further stress on the plant which in turn will take longer to re-establish. Make sure that the tree is planted to the same depth as it was in the field.
Fig.2 Containerised Trees. Once removed from their containers, trees should be planted immediately: exposure to air and light is harmful to fine roots and should be avoided. Place the tree in the hole as shown and remove any spiraling and matted roots which form on the bottom of the container.
Fig.3 Backfilling Hole. The base of the hole must be firm, so that the tree will not sink. Once the tree is placed in the hole, backfill with the existing soil, firming it in to eliminate any air pockets. Ensure that the top of the root ball is level with the ground. Create a saucer or levy around root ball so that water will penetrate the root ball and not simply run off into surrounding soil.
Fig.4 Planting Into Clay Subsoils. It is very important not to disturb or dig into the clay subsoil. The greater the soil volume you give the tree to grow in the better it will perform and the longer it will live. The quality of imported soils varies greatly keep in mind that sandy loams used can be deficient in nutrients or can be leached out quickly.

Staking should only be done if absolutely necessary. Staked trees develop less calliper and a less robust root system than non-staked trees. A properly grown tree should have an adequate root to shoot ratio to anchor the tree firmly in the ground. Where vandalism is a concern, staking may be used as a deterrent. Where deemed necessary, trees should be staked at or below one third of their height. Ties and stakes should be removed after a year.

Stakes have the potential to rub against trunks and cause scarring; ties left on too long may become embedded in the trunk and cause ringbarking.

Thorough watering in is crucial. Trees that have been used to a regime of daily watering in the nursery are susceptible to water stress once they are planted out and are no longer being watered so frequently. During the first few months, or for longer in the warmer part of the year, it is necessary to water the trees deeply and regularly.

Frequent light watering will encourage superficial roots that will be prone to drying out. A drip irrigation system is the most simple and effective means of watering trees thoroughly. Do not over-water plants - in heavy soils that do not drain freely, water may accumulate in the planting hole. This should be avoided by proper soil preparation before planting takes place.

Irrigation systems should be programmed to include separate watering for trees as their root profile is deeper than that of other newly planted plants and their water requirements are different. A common mistake, especially when planted in a lawn, is to water the lawn rather than the trees.

Mulch trees to limit evaporation and to minimise weed competition. Mulch in contact with the tree trunk may cause rotting; to prevent this, mulch should not be placed right up to the tree trunk. Mulch placed over the surface of the root ball should not be so thick that it prevents water from reaching the root ball. Ensure that ties and stakes are not causing damage such as abrasion or ringbarking.

It is very important to monitor drainage and irrigation once the tree is planted out. This is especially important through the first growing season. Early recognition of potential problems can be resolved before they become detrimental to the long-term health of the tree.