An example of an exposed site which will regain its stability and wildlife values when planted using the techniques described on this page.

The first steps

• Seek advice about suitable species and their site-requirements from local people, nurseries, DOC or Environment Canterbury.
• Draw a plan showing the project area's natural features - the drainage pattern ... the better soils ... the sheltered places. This plan will help identify the sites with the best likelihood of success.
• Ensure the site is well fenced and protected from domestic stock.
• Keep a diary of work done & a calendar of proposed events as references if your project is to be undertaken over several years.

Plant material

Only good quality plants are suitable for exposed sites.

Bare-rooted conifers should look healthy, be hardened off and have well developed root systems with a root/shoot ratio of at least 1:3. Plants destined for areas with an unsynchronised planting season may need to be chilled for 2 or 3 weeks. Generally, one-year-old Pinus radiata is recommended although topped 18 months old plants may be preferred on sites which are very exposed. Other bare-rooted conifers should, in most cases, be 2 years old.

Native plants should be propagated from local seed sources. (These plants tend to perform best plus using these ecosourced plants helps preserve each area's unique biodiversity.) Because of their good root-forming features and ease of handling, Rootrainer-grown natives are recommended.

Succession planting

Best results with natives on exposed sites occur when emergent and canopy species are planted a year or 2 after the colonising species are established and providing shelter. This technique, which imitates nature, is known as succession. Contact DOC or Environment Canterbury for further information.

Deep cultivation

Trees, like other crops, respond to cultivation by making strong root growth. Plants on cultivated sites establish quickly and consequently lose their vulnerability to frost, rabbits and drought earlier. Deep cultivation is undertaken during summer when the soils are drier. Where it is difficult to get machinery on to sites with compacted soils, good sized planting holes for each seedling may be dug and cultivated by spade.

Spacings/species

Environment Canterbury has published a series of useful brochures which give practical advice on species and spacings. These are available at no charge. Contact Customer Services.

Fertiliser

The use of fertiliser (which can induce excessive top growth without a proportionate increase in root growth) is not usually prescribed although slow-release NPKS pellets may be added to the planting hole on sites with low fertility.

Control of weeds

Removing the competition for moisture by weeds is essential for successful planting results on exposed sites. A number of control techniques - manual and chemical - are suitable.

Mulching usefully restricts weed growth but organic mulch (straw, sawdust etc.) can absorb rainfall and is not generally recommended on very dry sites. Hard mulches, such as rock, help retain moisture on exposed sites and will direct rainfall to the root zone. Other products used as effective mulches include carpet and layers of newspaper. Check with Environment Canterbury to see if biocontrol agents - friendly insects and fungi which attack unwanted plants - are available for release.

A mix of eg 'Roundup' (100ml/10lt) and 'Pulse' (10ml/10lt) gives good weed control and should be applied, several weeks before planting. Individual one sq m 'spot' spraying is effective as the surrounding unsprayed vegetation gives shelter from wind and sun.

Shelter

In some situations, woody weeds such as willow and adult gorse can provide shelter on exposed sites and may be retained until the new plantings are self-reliant.

Planting

Bare-rooted conifers such as Radiata pine should be planted with a specialist tree planting spade which has a tapered, sharpened blade. The spade is used to cultivate the ground to a full spade depth to allow good root penetration without distortion. The seedling is then inserted and lifted 2-3 cm before being gently firmed as illustrated below. On very dry sites, seedlings may be planted 4-8 cm deeper than the nursery level (up to 1/3rd of the stem-length of a 1/0 seedling) without ill-effect. Bare root seedlings must be planted during winter - June/July/August.

1. open hole in cultivated soil
2. place seedling and fill
3. pull up and firm

Natives grown in "rootrainers" require a hole twice the size of the root mass and the tip of the root block should be cut off to encourage a strong fibrous root system. Rootrainer stock should be planted during Spring - September/October/November.

Rootrainers

Open rootrainer, taking care not to disturb the soil block. Remove 2-4 cm at the base of the soil block with a sharp knife or shears. Plant in well-cultivated ground, covering the soil block. On very dry, free-draining soils, slightly "dishing" the surface of the planting hole helps direct moisture to the root zone.

Maintenance

Before commencing your project, ensure you have the resources available for post-planting maintenance:

• Regular noxious weed control.
• Annual replacement planting if mortalities exceed 20%.
• Ongoing animal pest inspections and control if required.
• Optional watering by hand to maintain soil moisture levels.

Trickle irrigation

Trickle systems are a useful aid to establishment but are not a cure for using inappropriate species on difficult sites. Systems should be calibrated to deliver 10 lt of water to each plant every 10-15 days.

Water control

On wet sites, diversion structures or channels will carry away surplus water from gully heads and other eroding areas.

Tunnel gullies may be plugged with straw (which acts as a filter to trap eroding soil) and planted.

Animal pest repellents

Commercial repellents are available from nurseries or can be made by dissolving 80 g egg powder in 80 ml water (or 5 eggs in 600 ml of water), mixed in 150 ml acrylic paint. 20 ml of this preparation is sprayed on and around each plant. A repeat application may be required.

Glossary

Harden off

- Term used for the nursery practice of introducing seedlings to harsh weather conditions.

Ecosourced

- Plants raised from seed or cuttings obtained from parent trees growing within a several km radius of the project site.

Biodiversity

- Term used to describe the diverse range of plants, animals and the habitats they share.

Emergent species

- Tall forest species eg Totara, Rimu, which grow above the forest canopy.

Canopy species

- Intermediate-sized trees and shrubs eg Matipo, Kanuka which form a dense overhead cover.

Colonising species

- Hardy shrubby species eg Flax, Cabbage tree, established in the project's first year, to nurse subsequent plantings.

Succession planting

- The timing of planting stages to reflect the natural sequence of forest development.

Before and after...a barren corner of Environment Canterbury's Timaru office site transformed.