Planting Advanced Trees

The success of planting any plants and particularly advanced trees is substantially dependent of proper planting procedures being followed. Don’t spend $100s on the plant and only Cents on the planting site. In the Nursery Plants and Advanced trees are highly managed pampered plants, sticking them in poorly prepared and maintained planting sites will inevitable lead to poor establishment and/or growth rates at best, but to failure and death in many cases.

With advanced trees you are buying TIME, perhaps 3 – 25 years. To protect that investment you need to plant properly.

A principal cause of poor establishment of advanced trees into the landscape is the incompatibility between potting mix and planting site soil. The degree of difference between the Air Filled Porosity of the Potting and Site media leads to a number of problems that see the trees fail to thrive or die.

Planting sites soils fall into two main categories: Undisturbed and Disturbed.

Prior to planting any tree into a planting site the following pre-treatment should be implemented on the root ball:

• Trim all sides and across its base. Using a sharp spade or blade, cut the outer and under surfaces of the root ball away to a depth of about 20mm. With non-Air Root Pruning Containers make 4 equally spaced radial incisions, to a depth of at least 50% of the root ball radius radially into the root ball. Cutting vertically down the radial edge from the top to the bottom. These procedures will sever any circling or girdling roots. The root trimming will stimulate new adventitious roots and the plant will colonise the planting site faster. Formative pruning of the crown also recommended at this time.

The structure, nutrient, Ph and biology are also often overlooked in the planting process. These are all critical factors in a trees health and productivity. Remember there are two factors that come into play that govern the success of any tree in the landscape. Vigour is the genetic capability of a tree to resist strain. Vitality is controlled by the environmental conditions that it finds itself.

Using a Shigometer and Vigour probes you can determine the relative vigour of one tree to another of the same species. Soil testing for Ph, nutrients, microbiological activity and observing soil meso fauna will identify the adjustment that are required to the environment into which the tree is to be planted. All these test, which should be implemented prior to planting, are readily available at low cost.

1. Planting in Undisturbed soils;

1.1. Planting in Undisturbed soils is relatively simple, but uncommon. The undisturbed soil will normally have clear Horizons:

• “O Horizon – Organic Layer,
• “A” Horizon – topsoil
• “B” horizon – subsoil

1.2. Most soils are shallow 100 to 200mm of top soil over the subsoil. Planting will often require an excavation depth that enters the subsoil. When planting in undisturbed sites check the subsoil depth and determine its degree of free drainage. If the subsoil drains poorly determine its depth and compare it with the depth of the root ball. If the root ball will reach or enter into the subsoil layer, which is poorly drained implement one of the following procedures;

1.2.1 Excavate the subsoil to the depth required to accommodate the depth of the root ball,

1.2.2 Establish a drain that will ensure that water does not remain in the well excavated for the tree within the subsoil. Water retained in this well will saturated the high organic media, such as that used in the production of advanced trees, leading to anaerobic conditions the production of Arsenic that will kill the roots and potentially the tree,

1.2.3. Using a trenching machine make a series of cuts to create a planting site that is to the depth of the root ball and 1.75 to 2 times the diameter of the root ball diameter.

1.2.4 A trenching machine will crumb the soil enabling it to be easily modified and or handled and avoids the hole glazing where an auger is used. In clay soils If you use and Auger to prepare planting sites, excavate deeper and break the side down using a crow bar to remove the glaze,

1.2.5 If you can’t drain the planting site sub soil establish the bottom of the root ball at the sub soil surface and raise the surrounding soil for a distance of 1 – 2 m from the tree centre line.

1.3. Standard planting preparation procedure;

1.3.1 Prior to planting any tree into a planting site the root ball should be trimmed on all sides and across its base. This is achieved using a sharp spade to cut the outer surface of the root ball away to a depth of about 20mm.

1.3.2 With non-Air Root Pruning Containers make 4 equally spaced incisions, to a depth of at least 50% of the root ball radius, radially into the root ball. Cutting vertically down the radial edge from the top to the bottom..

1.4 Prior to Planting Sites;

To assist with establishment and long term health of the tree preparation implement the following procedures;

1.4.1 Excavate the correct site, establish a hole of equal depth the the root ball and between 1.75 and 2 times larger in diameter.

1.4.2 Fill the planting site hole with water and allow it to drain, should empty within a half to one hour. If longer establish a drain or sump.

1.4.3 If the tree or specifications require staking; Install at least three and preferably 4 – 50x50x2.1m hardwood tree stakes or Sub surface Anchors

1.4.4 Place the tree into the planting site,

1.4.5 Tie off the tree to the tree stakes,

1.4.6 Refill the planting site with water, after the water has drained away,

1.4.7 Backfill with the excavated soil, in 50 to 75 mm layers and lightly tamp each layer. See Backfill Specification Below point 1.5

1.4.8 When backfilling is to ground line, make a well with some additional soil arround the outer edge of the planting pit,

1.4.9 Fill this well with water and allow to drain,

1.4.10 After settlement of the backfill, top up as required.

1.5 Planting Site and Nursery Pot Media have very different Air Filled Porosities.

Amendment of the planting site soil is essential to ensure healthy and rapid colonisation of the planting site by new plant root system. As we can’t and don’t need to change the Air Filled Porosity of all the site soil what we need to do is establish a transition layer between the Root ball and the Planting site soil.

Following the planting procedure is as set out above in points 1.4.1 to 1.4.9 modify the back fill according to these directions.

The aim of this procedure is to avoid a sudden transition from one soil type to the next. To achieve this, the excavated planting site media will be blended at various rates with a soil amendment media of the similar Air Filled Porosity as that used to grow the advanced tree.

The perfect back filling sees three transition layers established between the root ball of the tree and the site soil. These transitions will each be about a third of the space between the outer edge of the root ball and the edge of the planting site:

The three mixes will comprise:

• 75% Potting media and 25% site soil,
• 50% Potting media and 50% site soil,
• 25% Potting media and 75% site soil.

The first mix will be placed against the root ball, then second, and finally the third out to the edge of the planting site. Each layer should be substantially the same width, then procedure 1.4.6 to 9 should be implemented as set out above.

The greater the Air Filled Porosity difference between the site media and the potting media the more diligently this process should be followed. So for very porous sands or impervious clays this process should be followed closely. Watch for poor drainage in heavy clay soils.

In Sandy Loam to Clay Loams blending Planting site media with 40% by volume of Planting Amendments should be adequate. However, do a small test mix and look and feel the result.

It should be remembered that planting a plant or trees grown in potting media into planting sites of very low or very high Air Filled Porosity (Clay or Sand) will both cause the planting to fail unless special care is taken. In clay the root ball can go anaerobic killing the roots and in sand the water simply runs arround the root ball without wetting it, due to the hydrophobic nature of organics. Trees with dead roots have the same drought effected crown symptoms and trees with dry root balls. So before you add water to a plant that looks drought effected dig into the root ball and check the soil conditions.

In both site conditions amendment of the site soil will eliminate the hard interface between the root ball and the site soil. Amended Planting site media will allow moisture to get into the root ball, while allowing excess water to drain away. This sustains the original roots system of the plant while it colonise the planting site.

1.6 Watering how much and when:

1.6.1 Supplementary Water;

All plants and Trees will require additional water until they can establish into the planting site media. The larger the plant or tree the longer the watering support will be required. In the nursery plants are watered as require by climatic conditions. Small plants often twice a day while In the case of advanced trees in containers of 50 to 1000 litres watering may range from daily, to every few days, to a week or more. What is important is the quantity of water provided and the water holding capacity of the medium.

The amount of water delivered is normally measured in relationship to the evapotranspiration rate of the area. This is easily found on the Bureau of Meteorology web site. Thus the quantity of water required can be determined for each planting site location. Most Melbourne areas fall in the 1200 to 1400 mm of evapotranspiration per annum. Typically the following evapotranspiration rates can be expected for the following months.

Thus per sq meter of root system a plant will typically require the following water for each Month. However this will depend on soil type, exposure, drainage etc. This is a guide only.

In normal years water may be required to be applied from October to March. This would best be done on a monthly basis, allowing for the applied water to soak into the area to be watered. That is the water must soak deep into the profile, not spread out over a larger surface area. A tree that has a root plate estimated at 1.76 M2 would require 1.76 times the monthly water requirement. That is in December it would require 352 litre of water to be added and soaked into the 1.76 M2 around the tree.

The calculation can be made for various sized trees in each of the months that additional water should be applied. It should be noted that rainfall during the summer months is normally of little benefit to newly planted and not yet established trees. Particularly where a grass cover exists, as this tends to shed the rain from summer thunderstorms. Extended periods of wet weather are required to allow the grass and the soil below to moisten, so allowing water penetrates deep down into the soil profile and root ball.

Trees come from various genera and species within the genera. Knowing where the tree came form will give you some indication of the water requirements. However, be carfull with this calculation as soil type in the natural and the planting site are a major factor. So a desert tree with little rain fall may not be drought tolerant if it grows in dry river beds where free water is only a few meters below.

1.6.2 Water tubes

Plastic drainage pipes set vertically into the soil at four locations around the boot ball and down to the depth of the root ball can assist with watering the trees. This practice can be further enhanced by the incorporation of a gravel patch around the base of these pipes that acts as a reservoir. The water can then be allowed to soak away into the root ball and surrounding soil.

The correct amount of water require to saturate the profile is essential for proper supplementation. Little and often watering is not a satisfactory it waste water and is easily evaporated from the soil. The water should be applied so as to saturate the soil profile to be watered and then left to dry down. The saturation of the profile drives out all the carbon dioxide from the soil and as the water drains down to field capacity it sucks back in oxygen. This is how soils breathe. Constant topping up of soil moisture limits the oxygen in the soil and leads to root death and tree decline.

1.7.1 Soil Amendment Example.

Product Name: Rivett’s Nursery Planting Site Amendment.

Available through: Your preferred nursery supplier.

Type B1 – Basic Mix.

• Standard packaging 40 lt poly bags estimated @ 20 Kgs,
• Pallet Lots 50 Bags,
• Also Bulker bags 1 m3.

Basis mix will comprises:

• 60% Pine Bark fines, 40% coir, 10% wood chips, 5% Deep litter Chicken Manure, 5% Basalt Rock Dust, 5% Humates.

Augmented Mixes:

• Heavy clay soils Gypsum supplement – Bulk Bags only.
• Low fertility sites elevated nutrients – Bulk Bags only.
• Trace elements – Bulk Bags only.
• Biologicals. Sachets in boxes of 500. Std Rate 1 sachet per 20lts of root ball,

1.7.2 Planting site dimensions and Augmentation Volumes by container size

Budget cost example:

• The budget plant cost ex nursery for a 30 lt root ball tree will be say $100 ex GST
• A 30lt root ball (40cm pot) in a sand and clay site,
• Would require a amendment mix of 40% of the planting site excavated volume.
• So for a 30 lts root ball there will be a 92 lt of back fill volume,
• At 40% of Amendment mix will be required 37 lt of Amendment blend,
• At a cost per litre at a bulk cost $0.15 c/lt the amendment cost will be
• 37 lts x $0.15 would equal a cost of cost $5.55 plus gst.
• Which is a percentage cost of 5.55% with a benefit of an established tree
• These costs are pre delivery and planting costs and will be more than offset by establishment rates and reduces maintenance cost. This is a very cost effective investment ensuring rapid establishment, plant health and survival.

1.7.2 Planting site dimensions and Augmentation Volumes by container size. Cont:

Further Planting information is available on:

• Soil Health and Nutrition,
• Mulches,
• Maintenance