How to plant trees
Tree establishment on Australian farms
What I do
Getting your trees in the ground your own way
There are many ways to plant trees on farms and every experienced tree grower will have their own views about what’s best for them and why.
If you want a large monoculture plantation then an industrial forestry approach - with bull-dozers, broadacre chemical applications, planting crews and tiny ‘speedlings’ - is probably the way to go. But what if, like me, you plan to plant 500 to 2000 trees each year of a range of different species set out in strategic planting designs (rather than blocks)? In this case, what’s best for the forestry companies is unlikely to be the most appropriate for you.
World’s best forestry practice: Deep rip, mound , spray herbicides over the rows, control vermin, plant small seedlings from cells, fertilise and stand back!
Before making any decisions you should think about your site, the number of trees you want to plant, the species and planting stock available, the machinery and tools you have on hand, the time of year you want to plant, who will be doing the work, and your attitude towards using chemicals and fertilisers. Sound’s complicated? It’s not really. You just need to understand the principles of tree establishment and the pros and cons of the various options.
The choice of planting stock
Having decided to plant a particular species you may be faced with a range of stock options: pots, tubes, cells or open rooted trees. The cheapest are likely to be 1-year-old open-rooted seedlings (for conifers and deciduous trees) or trays of seedlings growing in small cells. Both must be handled carefully and planted quickly but have the advantage of being very light and easy to carry. Special planting tools are available for the cells that mean you don’t even need to bend over, but the soil must be well prepared.
Tubes and pots are more robust and versatile. They can be held on site in anticipation of planting for much longer. Because tubes can be planted into most soil types without the need for cultivation they may mean you can save on the cost of soil preparation. If you are growing the seedlings yourself, then having them in pots means you don’t need to water them every few hours. Some specialty species also seem to do better if planted out as 2-year-olds with a well developed root system.
What I do: All the eucalypts and wattles I buy are in grown in cells. They are cheap and easy to plant into our soils using a poker stick. The pines and oaks go in as open-rooted seedlings using a spade. Specialty trees such as bush foods or rainforest trees are usually grown in small individual pots. The redwoods I grow on for 2 years before planting are in large 8-inch pots. It’s ‘horses for courses’.
Getting them in the ground
I like to start by identifying the limiting factors that are likely to impact tree survival and growth. Invariably it gets back to four factors: weed control, soil conditions, climate and protection.
1. Weed control
When planting trees a weed is anything that competes with the seedling for moisture or light. Removing competition using chemicals, mulch or cultivation is essential to ensure survival and will certainly improve growth. Almost every novice tree grower makes the mistake of not having sufficient weed control – it is a lesson we all learn the hard way.
Simply mowing the grass around the seedling is not weed control. In fact, this will only encourage the grass to stay green longer and dry the soil out more. Fertilising and watering only encourages the weeds and should not be done unless the weed control is perfect: We are talking here about the total elimination of all plants that draw moisture from the soil around the seedling. If you don’t want to use herbicides you must find an alternative be it mulch, weed mats or cultivation.
The area of weed control required and how long it must be kept wee-free depends on the rate of growth of the trees and the predominant weed types. In most cases trees provided with a full growing season of weed control (within 1m of the tree) will be strong enough to fend for themselves. Weed control in the second and subsequent years is only justified where tree growth is very slow or there is extremely vigorous competition from deep rooted grasses or woody weeds.
What I do: I use herbicides. I’ve tried mulching but it’s just too much work. I mix a knock-down chemical (like Gyphosate) with a pre-emergent (like Simazine) in a knapsack and spray spots (about 1.5-2m in diameter) a month or so prior to planting. This provides a weed free area for up to 12 months on our place. For the deciduous trees and slow growing specialty species I do a follow-up spray in the second season to ensure they have another year free of weeds.
2. Soil conditions
Waterlogging, hard pans, non-wetting sands and other soil limitations will influence the choice of site preparation and planting technique. On some sites, survival and growth will be very poor unless something is done about deep soil structure. The best way to find out is to ask around – neighbours, commercial contractors or landcare groups. If they do deep rip or mound then ask why and whether or not they have tried planting without doing it.
If you have access to a back-hoe you can dig soil pits. Look for heavy clay or buck-shot layers, bands of mottled soil that indicate waterlogging or other indications of compaction down to at least 1m. In some cases a hardpan close to the surface can be broken open with a tractor ripper. If it is deeper than about 30cm or very heavy then you’ll probably need a bulldozer. Mounding may be necessary if the site is waterlogged at the time of planting but be aware that this can result in the trees becoming unstable.
Many industrial plantation managers choose to use intensive ripping and mounding simply to reduce the costs of planting. Planting crews can work faster when planting into well worked soil. Good tilth may also allow open rooted trees or very small seedlings to be planted instead of tubes which are more expensive to handle. Cultivation can be used as a form of weed control and also releases a pulse of nitrogen as organic matter breaks down which can stimulate growth.
What I do: Given the range of species and irregular planting patterns I plant I cannot justify the cost of bringing in a contractor to rip and mound prior to planting. I also don’t like the lumps and bumps mounding leaves in the paddock for years and the thistles that come up after cultivation. I prefer to plant into undisturbed soil following spot herbicide application taking care to minimise disturbance of the top soil which carries the pre-emergent herbicide. My trees might grow a little slower in the first few years but I believe that any long term benefits of ripping and mounding will be lost on our site by about age 10.
3. Weather conditions and when to plant
In the southern states trees are usually planted in winter when the soils are moist and there is little risk of a hot dry wind. Open rooted deciduous trees and conifers are best planted close to the shortest day (July) because their roots start growing earlier than their shoots. Most of our native species are more opportunistic and are better planted just prior to when the growing conditions are best. Leaving them wallowing in wet cold soils over the winter seems to set them back a little. Some of the more sensitive species, like Spotted Gum, are best planted after the risk of frost has past.
In northern New South Wales and Queensland the timing of the wet season during the warmest months make it more difficult to know when to plant. The rains come in summer but it is hot. In winter it is cooler but frosts can be a killer. I like the idea of summer planting: when you see a good week of rains coming get out and plant. If you do need to plant on a hot dry day then do so in the late afternoon and water them in well before you leave.
What I do: I like to plant eucalypts and wattles in mid spring into warming soils. This also allows me to focus on achieving good control of the early spring weeds prior to planting. With good weed control there is no need to water the trees at all. As long as the weed control is done early there will be enough moisture held in our clay-loam soils to allow planting as late as November in some years.
The final important point to consider is the protection of seedlings. Rabbits, hares, deer, kangaroos and wallabies are common browsers of young trees along with domestic stock. Options for browsing control might include shooting and poisoning (where acceptable), repellents, tree guards, fencing or deterrents and will depend of the area, period of risk and landowners resources. There are no surprises here: know your enemy and be ready.
Insect damage on young trees can be extensive, especially during a late summer when the trees might suffer moisture stress or insect populations are high. Landowners should be aware of the risks and watch for signs of excessive defoliation. Although most species can tolerate quite high levels of defoliation if trees are repeatedly attacked treatment may be warranted.
Then there are the extreme weather events: heat, wind, frost, fire and flood. If the roots remain healthy, damaged seedlings can be cut back to a live bud and will grow back strongly – sometimes better than before.
What I do: My worse browsing pest are the wallabies. If I can effectively guard the trees from them I needn’t worry about rabbits or sheep. In an earlier article I described my wallaby guard. Defoliating insects can be a problem in young eucalypts but I tend to accept a degree of damage in preference to using insecticides. In most cases the trees recover although I may need to do some corrective pruning to re-establish a strong central leader.
Find what works best for you
As farmers gain experience in tree growing they are refining their tree establishment methods. I encourage farmers to start small and learn from their own experience. Imagine how much better you’ll be at growing trees after 4 or 5 years experience on your own place. Ny then you’ll also know what species you really want to grow and be gaining knowledge about how to manage them. Your trees will live for a long time – but only if they survive the first year!
What I do: I like to spread my risk. I plant a thousand of so trees of a range of species every year across a number of sites. I prefer to do all the work myself and not plan to plant so much that it becomes a chore.
No doubt you’ll come up with a method that suits you. Good Luck.
What I do: Spray a 1.5-2m diameter spot with pre- and post-emergent herbicides, plant directly into the undisturbed soil and protect the seedlings from wallabies and sheep with a long flexible tube. This photo was taken in early February and shows a eucalypt that I planted as a small seedling (from a cell) 4 months earlier. Note that the weed control is still effective ensuring that all the moisture in the soil is available to tap into as it grows. BUT: Rather than copy me you need to work out what works on your place.