» 1. Preparation of the Planting Hole

» 2. Root Ball Preparation

» 3. Backfilling

» 4. Drainage

» 5. Watering

» 6. Mulching

» 7. Staking of trees

» 8. Fertilizing

» 9. What a Difference Mulch Makes

» 10. Reasons Why You Should Dig a Wide Hole

» 11. Tree Planting Guide

» 12. Conditions That Can Affect Trees

» 13. Claims

» General References

1. Preparation of the Planting Hole

The size and depth of the planting hole are critical factors in the success of planting and establishing a new tree.

Holes should be dug with the diameter no less than three times the diameter of the root ball. This is particularly important in compact soils.

The hole should have sloping sides similar to a wok. This provides a greater volume of loose cultivated soil in which rapid root initiation can occur. Research has shown that plants benefit from larger planting holes. (Figure 1 & Figure 10)

A larger hole means a greater volume of loose cultivated soil that is not compacted but aerated which allows good water penetration for rapid healthy growth. (The majority of the roots on the newly plated tree will develop in the top 30-40cm of soil).

The depth of the hole should be equivalent to the depth of the root ball, do not excavate more than the depth of the root ball. If you do, firm down the soil immediately to prevent the root ball from sinking.

Planting too deep is a common mistake that leads to symptoms of poor vigor and slow growth that can often lead to plant death and or diseases for example cellar rot.

Figure 1 Cross section of a wok hole Showing sloping sides and top of Root ball level with ground.

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2. Root Ball Preparation

Before plating a tree, it should be watered in the container 3-4 times to ensure the root ball is well hydrated before planting.

Mt William Advanced Tree Nursery mainly uses pruned containers which minimize circling roots, but you should inspect all root balls for root circling and as a matter of cause, make a series of 34 cuts in the root ball from top to bottom to a depth of 23cm. (Figure 2)

If a mat of root exists on the bottom this should be cut off. The effect on shoot growth after this is minimal. But what it does do is help eliminate root circling and potential rood girdling and help regenerate new roots into the surrounding soil (Figure 3). If severe root pruning is required, monitoring water requirements is even more critical after planting.

Figure 2 Showing side cuts into root ball.	Figure 3 Trimming bottom of root ball

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3. Backfilling

Before starting to backfill, make sure the root ball is the correct depth, the top of the root ball should be level with the soil, and under no circumstances should soil be placed over the top off the rood ball (Figure 4).

Back fill in sandy soil is generally loose enough, in heavier soils it will need to be worked over and broken up so and not to create air pockets that could inhibit root growth. Back fill around the tree to about 2/3 lightly tampering the soil only, and then water. Back fill the remaining 1/3 and then water again.

What comes out of the hole is what should be used as back fill, once it has been well worked over. Unless the soil is so bad you have no other choice, use the existing soil.

Adding organic matter will improve structure (aggregation of soil particles), drainage and fertility in most soils but is not necessary to get a good result when planting a tree. But if you have extremes in soils, for example heavy clay or sandy soils adding some well composted organic matter may be beneficial. If organic matter is added, it should be no more than 30% and only added to the final 1/3 of back fill. If added it needs to be well mixed through the final 1/3 of back fill before placing into the hole.

Figure 4 Top of root ball should be level with soil

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4. Drainage

Water logging of newly planted trees is a big killer. This can be caused by poorly draining soils, and or simply by over watering. One of the simplest ways to determine poorly drained soils is to half fill the hole with water, if the water remains in the bottom of the hole and has not drained away after an hour or two, drainage may be a problem. If your area has been experiencing dry weather this should be done a couple of times to get a more accurate indication.

Good drainage from the bottom of the hole is very important for root regeneration and root penetration into the surrounding soil. The bottom half of the root ball and the back fill can be water logged during wet periods, or by over irrigating, even though this period of saturation may be for a short time only, it can still cause the death of tree roots. Water can drain into three holes from surrounding landscape and excessive watering of lawns can cause a build up of water, this not only happens in wet periods but even during severe droughts.

Trying to establish lawns and new trees at the same time should be avoided at all costs; you should do one at a time, either establish the lawn first then the tree, or vise versa. When trying to do both at once all you are doing is slowing killing the tree or retarding its reestablishment. Because of the large amounts of water required to establish a lawn, a large percentage of the water finds its way into a newly dug tree hole, causing saturation of the root ball and surrounding soil.

Solving drainage problems may be expensive, but it is essential for good plant performance and must be corrected before planting.

Improving drainage can be difficult at times and sometimes maybe cheaper to improve the drainage on the whole site rather than drain individual holes than plating large numbers.

One simple approach is to plant the tree with about 1/3 of the root ball above the ground level and then build a mound from the top of the root ball to the original ground level. A draw back of this method and something you must be mind full off, is the top 1/3 of the root ball and the mound may dry out quickly in hot, dry conditions so a top up of mulch and more frequent watering may be required.

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5. Watering

Water must be applied directly to the root ball in the months following planting, as this is where the majority of the roots are located. One of the best ways to achieve this is by building a basin or reservoir around the root ball to hold water (Figure 5).

Figure 5 Basin to hold water, formed outside the diameter of root ball.

This should be approximately 10cm-20cm high located in a circle at the edge of the root ball. This basin can be filled with water, which allows the water to soak down into the root system (Figure 6). By doing this you can monitor how wet or dry the root ball is and adjust the amount and frequency of watering accordingly.

Do not rely on automatic sprinklers or drip systems to provide the required amount of water for a newly planted tree.

No matter what system you use, regular checks are required to see if the tree is getting the correct amount of water. Checks can be made by pushing a wooden stake or steel rod into the root ball and the surrounding soil to check how wet the ground is. Another method is to dig down the side of the root plate to the bottom of the planting hole, this allows you to check the moisture content of the root ball and monitor if the water is draining away from the root system of the newly planted tree.

Figure 6 Filling basin with water, allowing soaking of root system.

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6. Mulching

Mulching is a very important part in the establishment of a newly planted tree. Mulch helps maintain soil moisture, acts as a buffer to soil temperature extremes, controls weeds and replenishes organic matter and nutrients the soil.

The mulched area around a new tree should be a minimum if 1.5m in diameter, but 2m to 2.5 would be ideal. The mulch should be 5-10cm deep after settling. The mulch used should be anything organic that is well-composted, for example wood chips that contain a blend of leaves, bark and wood. Pea straw is also very good (Figure 7).

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Figure 7 Mulch using good organic mulch.

Mulch should be applied so that it is not piled up against the trunk and the root crown is exposed. Under no circumstances use grass clippings or any material that is still composting and giving off heat.

Grass and tree roots do not mix they can be one of the biggest inhibitors of root development. Mt William Advanced Tree Nursery also advises against plating bulbs and shrubs under trees and in particular under establishing trees.

Most of the fine, absorbing roots are located within centimeters of the soil surface. These roots, which are essential for taking up water and minerals, require oxygen to survive. A thin layer of mulch, applied as wide as possible, can improve the soil structure, oxygen levels, temperature and moisture availability where these roots grow.

7. Staking of trees

Quality trees should not need stakes to keep the trunk upright. If stakes are required to stop the trunk from bending towards the ground, I would consider not planting that tree. Often there is a requirement to protect trees from vehicles, mowers, animals etc. If staking, make sure they are driven into the ground outside the root ball. If the trees must be connected to stakes for support for example in very windy conditions, the ties must be loose to allow trunk movement, as this is essential to stimulate caliper growth and correct trunk taper (Figure 8).

A tree with a large, dense canopy often requires staking until all roots can grow to sufficient length and density to anchor it. (Ed Gilman 1997). Customers must be aware that even slight movement can break the new fibrous roots and slow the tree establishment.

If trees are staked they must be check regularly to make sure ties are not too tight or that stakes are not rubbing on the tree. In most instances stakes that are sued for anchoring should be removed after approximately one year (Figure 8).

Depending on size, but 2 to 3 stakes should be used per tree. Mt William Advanced Tree Nursery advises to drive stakes in on an angle and per (figure 8) and well outside the root ball and into the undisturbed ground, this will prevent the stakes working in towards the trunk and causing damage. Avoid using any tie, which is too tight, as this may cause trunk damage and or not allow for trunk expansion.

If you do stake your tree please remember to stake only until it is able to stand on its own. If it is too dependent on supports, the trunk will not develop adequate strength. The staking material should not be too tight. Leave loose enough so some natural movement occurs.

Figure 8 Staking trees using Hessian.

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8. Fertilizing

It is difficult to make a general recommendation about fertilizing after planting that would apply to all situations. Fertilizing generally provides little benefit in the establishment of trees except in nutrient deficient soils. Until the roots systems of newly planted trees regenerate and depending on conditions this can be weeks or months, this will govern how effective any application of fertilizers would be.

Unless the soil is nutrient deficient, it is best to wait several months up to a year before fertilizing.

The root systems of newly planted trees can be easily burned by fertilizer, leading to poor performance.

Spreading a fertilizer high in nitrogen over the mulched areas can help reduce the loss of nitrogen caused by microorganisms breaking down the organic mulches.

Mt William Advanced Tree Nursery advises to fertilize on the surface when soil testing indicates poor soils have nutrient deficiencies once the tree is established and actively growing.

Most trees tolerate a wide range of pH levels but as far as nutrient supply is concerned for natural soils, a pH range of 5.5-7 should be suitable for most plants. Levels outside this range can affect availability of nutrients held within the soil, toxicities and the activity of soil microorganisms. (Handreck and Black, 1994) 

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9. What a Difference Mulch Makes

These two trees were plated at the same time, the tree in Figure 9 never had grass planted but mulched straight away. The tree in Figure 10 had grass planted and watered more frequently to keep the grass alive. This tree was much worse and only improved when watering of grass was stopped due to restriction. Initially the tree in Figure 10 would have been over watered. The tree in Figure 9 was mulched and only watered when required.

Figure 9 Mulched Tree	Figure 10 Not Mulched.

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10. Reasons Why You Should Dig a Wide Hole

• The width of the hole should be two to three times the size of the root plate of the tree you are planting. (Diagram 3)
• The hole should be wok shaped, so the roots can spread horizontally near the surface where optimum growth takes place.
• A small planting hole (Diagram 1 and 2) can hinder plant establishment. The regenerated root system will have very little space to grow before encountering compacted and low oxygen soils, which inhibit root growth.
• The roots must ultimately spread beyond the planting hole. If the site soil is compacted and difficult to penetrate, the roots may circle inside the hole (Diagram 1), just as they can do inside a hard walled pot. If roots are unable to grow into the compacted sub-soil, a hole with sloping sides will allow roots to grow back towards the surface and continue to spread.
• Optimum root growth requires soil oxygen levels in excess of 15%,root initiation requires oxygen in excess of 12%, and growth of existing root tips requires in excess of 5-10% (Biddle, 1998). So therefore by digging a wider hole with sloping sides opens the soil up to the atmosphere to allow diffusion of oxygen (Perry, 1993) This gives the root system a greater volume of loose cultivated soil that is not compacted but aerated which allows good water penetration for rapid healthy root growth. (Diagram 3).
• Better to plant a $100 tree into a $200 hole rather than $200 tree into a $100 hole. Make your first expensive the best expensive. Take the time and money to get it right.

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