Why restore a forest?
There are lots of reasons: it's rewarding; it stops soil erosion and improves water quality; it provides food and habitat for birds and insects; it can recreate a sustainable forest in an area where virtually all native forest has disappeared; it can increase the chances of survival of endangered plants; it can also lessen the effects of extreme variations in local climate and act as a sink for carbon. And it looks wonderful when you've finished!
Revegetation is simply re-establishing a cover of native plants using local species and stock. Ecological restoration, however, has the further aim of restoring the land to something approaching the original forest characteristic of that landscape. Here, special attention is placed on replanting each tree species on specific sites to mimic the natural forest pattern.
You should aim to ensure that your restored forest will survive and eventually contain the range of species normally found in the area.Use plants that have been sourced locally, generally within a range of 50 kilometres. New Zealand has been divided up into Ecological Districts which can be used as a guide for seed collection too. However, some species such as kahikatea and mapou (matipo) don't alter much over larger areas, and others such as kowhai may vary over very short distances. Get to know your local plants! Special care needs to be taken with plants from specialised or unusual habitats such as coastal areas, rocky bluffs, by hot pools. Always collect seed from a variety of plants of each species to maintain genetic diversity. Don't take an excessive amount of seed from any one tree.
For the best results, planted trees should be naturally sited. They need not be at the same abundance levels as in your "textbook" forest. The composition of the forest will change many times anyway before the climax forest is reached.
Any piece of land is worth restoring, but if you have a choice some areas are better than others. The best ones are those next to existing bush or scrubland, especially if they connect pieces of existing forest or fill in gaps. Other good areas are those next to streams and rivers, also gullies, wetlands and coastal areas. Any land where erosion will be prevented is good. If you do not have your own site, ask the Department of Conservation or local councils if they are aware of areas in need of restoration.
Fencing: Your plants need to grow in a safe environment. Make sure the site is securely fenced to keep out stock and goats. An electric fence may be needed.
Animal pests: Identify all animal pests in the area. Possums eat some young plants. Timms traps are a convenient way to trap possums, or ask advice from your regional council pest officer. Hares love tender new plants and will snap off quite large stems. If total eradication of these pests is impossible, make barricades with sticks (particularly prickly ones) around the plants. There are some sprays available, but these are expensive and need to be repeated frequently. To start with, plant things pests don't like such as manuka.
Weeds: These are the biggest threat to our forests and young trees are particularly susceptible, even to long grass. Identify all weeds in or around the area you want to restore (and where you grow any plants!). Persistent invasive weeds to look for are things like privet, ginger, wandering willie, asparagus fern and ivy. Ask your regional council pest officer for advice. Getting rid of invasive pests is a priority and it takes effort. If they are really bad you may want to amend your ideas of restoring that particular area. Your dream forest could end up a major source of weed infection for adjacent areas. This is not a good way to make friends with neighbours! If you go ahead, practice weed hygiene. Get rid of existing weeds and use only weed-free plants and equipment.
For the most effective regeneration, you are aiming to establish a nurse crop that will rapidly cover the area and provide protection for the next stage. So at the start you will need a lot of plants that are cheap and easy to grow. You may need to experiment a bit. To find out which method suits your site best, have a look around your area to see what grows naturally, which young seedlings come up easily. Look where they are growing and learn from them. At the start you will be particularly interested in ones which appear to be able to survive frosts, droughts, floods, possums and other such threats. So use your nearest local forest as your "textbook", provided it's similarly situated.
- Encourage the growth of large numbers of early colonisers to establish a nurse crop. Good plants are manuka, kanuka, coprosma, cabbage trees and flax.
- After the nurse crop is established, encourage shrub forest. Plant many low canopy trees such as mahoe, Pittosporum, lancewood, wineberry.
- To achieve a natural, mature forest canopy, plant a few canopy trees in specially selected sites: rimu, kauri, matai, totara, puriri, etc.
From scrub or gorse: You already have protection for other more tender plants. If the gorse is very large and thick you may need to remove some to provide more light for growing plants. You can introduce a wide variety of species, including frost-tender ones. Your plants will eventually smother the gorse by cutting out the light it needs.
From bare soil or grass: Here you need to establish a nurse crop first. Manuka seed can be sown directly onto bare, firm soil, especially poor soils. For very large weed-free areas it is possible to heavily disk the ground to expose the underlying clay which manuka loves. Manuka seed can be collected at virtually any time of the year, but avoid sowing it so that it germinates just before or during periods of heavy frost. This will lift the tiny seedlings and kill them. Cut twigs of manuka with ripe seed capsules (don't destroy the whole plant!) and store in a dry place (eg on polythene on a shed floor) or expose to the sun on a tray. The capsules will burst open and the fine seed will fall out. You may need to give the twigs a shake. Another method is to place the twigs or branches directly on the bare ground. Anchor them on slopes.
Grow lots of manuka or kanuka in root trainers or even in milk cartons. When planting out keep the roots moist and disturb them as little as possible. A quick, inexpensive way to grow lots of manuka is to grow it in mushroom trays. Put more holes in the bottom, line with newspaper, even use strips of cardboard to form rows, add potting mix and press it firm, then sprinkle seed along the rows. They will need sunlight, water and airy conditions to prevent fungal growth. Break the manuka into clumps for planting, the clumps being large enough to keep the roots of the inside plants undisturbed. There is no need to mulch manuka.
Plant lots of flax, particularly around edges, bad erosion spots, and for shelter for planting other things. This is cheap and effective, particularly if you have a nearby supply of large plants which can be cut up. Trim the flax before planting and plant firmly as they tend to be top heavy. The flax will also bring in birds which will disperse native seeds from any adjoining forest and do the job for you. Flax is not always a natural early coloniser, however the maturing bush will eventually crowd it out.
Other good early colonisers are cabbage tree and coprosma species, but get rid of all animal pests first. Study your area. If you have forest with karaka you may notice that it comes up readily in grass around a tree. So try direct seeding in grass, making sure the seed is lying firmly on its side on the ground.
Encourage bracken. This is a long-term way to get back to native bush, but nature uses it to good effect as the bracken builds up a good layer of humus for future plants to enjoy. Your site needs to be adjacent to existing bush so birds can bring in the seed.
To determine the ultimate forest type you are aiming for, study remnant forests in your district that:
- have a similar topography, landform and soil type (eg both north facing, same slope)
- are in the same climatic belt (eg coastal, inland, upland)
This will help you create a picture of what the original forest must have looked like, and what a new successful and sustainable forest might be. And having got to this stage you can select a variety of other plants from your forest "textbook" which will grow in the shelter of your early colonisers or nurse crop. This will help to restore the natural biodiversity. Be careful with plants that well-meaning people give you. Check where they have come from; are they weed-free; make sure they are natives!
Find out from your forest "textbook" which succession of plants is appropriate for your site.
Dry Ridge: kanuka - tanekaha - kauri Hill Top: rewarewa/kamahi - hinau/rimu Side Slope: bracken - ponga/mahoe - tawa/rimu Easy Country: manuka - lancewood - totara/rimu Valley Bottom: manuka - coprosma - matai/kahikatea On Humus: wineberry - broadleaf shrubs - rimu/totara/tawa
For the nurse crop, it is important to plant densely - a metre or two apart. The plants will then support each other and you will get a rapid canopy and avoid weed problems. Restore small areas at a time rather than try a larger area with too few plants.
Clean spades and boots to avoid the spread of weed seeds.
Make sure holes are larger than the root ball. Press in firmly but avoid damaging the bark and branches. Staking can help you find the plants more easily when you go back to check them. Mulching keeps down weeds and provides nutrients for the plants. Use grass clippings, newspaper, old carpets, hay, etc. Remember that if plants are not put in properly you have wasted a lot of time raising them. This, along with plant and animal pests, is one of the main causes of low survival rate.
The best time of year for planting depends on the temperature and moisture content of the soil in your area. In general, plant as much as you can in autumn in drier, warmer places, but wait until the soil is moist. In frosty places plant in spring, though your plants may need water over summer. If you live in a wet, cold, higher altitude area, even summer may be the best time!
Don't neglect your plants once they are in the ground. Shortly after planting, check them for signs of animal pests and weed invasion and deal with the problem. Make regular checks, especially over spring and summer. Keep an eye out for your first naturally introduced seedlings!
- Gardening with New Zealand Ferns, Muriel Fisher, Collins, 1984
- Growing New Zealand Alpine Plants, Joe Cartman, Reed Methuen, 1985
- Growing New Zealand Plants, Shrubs and Trees, Muriel Fisher & ML Forde, Bateman, 1994
(prev editions with other co-authors may be available in libraries)- Native Forest Restoration, Tim Porteous, Queen Elizabeth the Second National Trust, 1993.
- New Zealand Native Plants for your Garden, Julian Matthews, Pacific, 1987
- The Cultivation of New Zealand Trees and Shrubs, Lawrie Metcalf, Reed Methuen, 1987
- The Cultivation of New Zealand Plants, Lawrie Metcalf, Godwit, 1993
- The Propagation of New Zealand Native Plants, Lawrie Metcalf, Godwit, 1995
- The Quickfind Guide to Growing Native Plants, Andrew Crowe, Viking, 1997
The preparation of this document was made possible by a donation from the Roy McKenzie Foundation.
