'Tubestock' is the term for seedlings that have been raised in small nursery tubes, for transport to the planting site. Propagation of seedlings can be by seed, by cuttings, or through division. Seedlings can be planted by hand or with a mechanical seedling planter at the prepared site.
As with direct seeding, site preparation is essential and will involve weed control and fencing. Even though tubestock planting is more expensive and requires more labour than direct seeding and natural regeneration, it is a widely used method of revegetation. Results are reliable and immediate, and plant placement is controllable. Because of the labour-intensive nature of tubestock planting (both in propagation and planting), fewer plants tend to be planted than with direct seeding.
Tubestock protected by tree guards showing mounding and excellent weed control on mounds.
In the old days, tree planters used plants grown in six or ten inch nursery pots. They dug a huge hole, back filled with some loose soil and fertiliser, planted the tree and watered it in. A hard-working individual on a good day might be able to plant 100 trees. Forestry developed some new methods where trees were grown in cylinders of tin or plastic, allowing planters to carry many more trees and dig smaller holes to plant them.
A real breakthrough came with the advent of square, plastic "tubes" which could be easily carried and planted, took up less room in a nursery and more importantly, led to better root development. A further improvement came with plastic trays designed to hold multiple plants, which are designed to train roots to grow downwards (rather than circling the pot and which allow air-pruning of the roots. These tray systems are now the most commonly used system for growing plants for transplanting in the field. In some cases (particularly for pines) bare-rooted nursery stock are transplanted into the field.
There is a common perception with trees that "bigger is better" but research has shown that small plants suffer less transplant shock and
rapidly establish a healthy root system which encourages rapid growth. Provided the root ball does not dry out before the roots have grown, small transplants result in healthier plants. Tubestock, can be planted conventionally, by digging a hole slightly larger than the root-ball, placing the plant in the hole with the surface of the potting mix just below the soil surface. When backfilling around a new tree, make sure you get firm contact between the root-ball and the
soil. Any air gaps remaining will cause the roots to quickly dry out. Leave a slight depression around the tree in order to catch and hold moisture. You can then apply mulch, mulch mats, tree guards or watering systems as you require.
You can also use a specialised planting spade with tubestock or bare-rooted stock. This is a rigid spade which is inserted vertically into the soil to the appropriate depth and then levered forwards and backwards to create a slot or hole. The tree seedling is then dropped into the hole, and the soil is firmly pressed against the roots or root ball (usually with the planters boot). When planting bare-rooted stock this way it is common for the planter to pull upwards slightly on the stem to straighten out any kinks in the roots.
Specialised planters are also available that cut a hole to the exact shape of the root-ball being planted. The plant is then dropped in the hole, firmed in with the boot and mulched or guarded as required. These planters usually have a foot plate so they can be pushed into the soil to the required depth. After planting the soil plug is scraped, pushed or shaken out of the tool and then the next hole can be dug. The disadvantages of these tools are that on clay soils they leave the sides of the hole smoothly polished and impenetrable to emerging roots and it can be difficult to clean between holes. On very loose soils, the hole will not hold its shape and must be dug out with the fingers. On the whole, these are fantastic tools that make small scale plantings much easier and quicker. One of the best known tools is the Hamilton tree planter, manufactured in Victoria (Insert a picture). It is available to suit a range of pot sizes and types. Other planters of similar design and function are also available. These tools can allow a good planter to plant up to 500 trees a day.
For large plantings and where you want to save your back, you can use Potti-Putkis (or mechanical planting tubes). These are hollow tubes with a handle at one end, and an opening "beak" at the other. The beak is pushed into the soil with the aid of a footplate, then opened using a foot-operated lever. The seedling is dropped down the tube in to the hole and the tube is removed. As the seedling is being firmed in with the foot, the beak of the planter is closed by a thumb-operated trigger. The depth of the hole is controlled by an adjustment on the foot plate. Potti-Putkis with different internal tube diameters are available to suit any seedling type including square forestry tubes.A good planter, well supplied with seedlings, can plant up to 2500 trees in a day with a Potti-Putki. The main advantage is that they do not require the planter to bend over to plant the trees. They also do not polish the sides of the planting hole. Potti-Putkis require soft soil to be effective and are best used where the soil has been ripped, mounded or cultivated first.
|Mattock and shovel||Good for heavy clay or inaccessible sites||Hard on the back, slow and dangerous|
|Planting spade||Relatively quick. Best for bare-rooted stock.||Requires soft soil. Requires bending|
|Hamilton planter and similar.||Easy to use and matches shape of root-ball.||Can leave smooth sides on hole. Clogs up in clay soils. Requires bending.|
|Potti-Putki||Very quick, no bending, good root-soil contact.||Requires well-prepared soil.|
There are a range of nursery containers currently used for growing seedlings. Each has its advantages and disadvantages, so it pays to specify the most appropriate container when you are ordering seedlings for your revegetation project. The following table compares common nursery containers.
|Plastic nursery pots||Usually 150 and 200mm diameter. Up to 1m diameter.||Retail sales of garden plants||Develop large plants, often to flowering.||Heavy, expensive, use lots of potting mix. Need a big hole for planting.|
|Plastic bags||Black plastic bags, usually 150 to 400 mm deep.||Often used with fruit or tropical trees.||Good for deep rooted species||Difficult to handle in the field, heavy, use lots of potting mix.|
|Speedlings||Rigid plastic trays of 100-250 plugs, usually 25 x 50mm each.||Vegetable seedlings, revegetation, starting nursery plants||Very cheap. Lightweight. Can handle lots of plants at once. Good root structure.||Vulnerable to dessication in nursery and field.|
|Hiko cells||Rigid plastic trays of 40 93ml cells, 100mm deep. Different sizes available.||Medium to large revegetation and forestry plantings.||Cheap, light, easily handled in field and nursery. Re-usable containers. Good root structure.||Cannot separate individual plants. Plants cannot be held in pots beyond season.|
|Lannen cells||Rigid plastic trays of 63 celss, 45 x 90mm, with side-slits. Different sizes available.||Medium to large revegetation and forestry plantings.||Cheap, light, easily handled in field and nursery. Re-usable containers. Good root structure.||Side splits make potting mix vulnerable to dessication. Cannot separate individual plants. Plants cannot be held in pots beyond season.|
|Forestry tubes||Individual square-sided plastic pots, 50 x 150mm.||Small to medium revegetation and forestry plantings.||Small, light, relatively cheap. Can provide individual plants.||Difficult to handle in large numbers in field. Can have poor root structure.|
For plantings of more than 200 plants, we recommend one of the tray systems (speedlings, Hiko or Lannen). Because of the small rootball volume, these systems can dry out quickly so it is very important to have a good watering system in the nursery and to water frequently in the field while planting. It is worth incorporating some water crystals into the potting mix with these trays, particularly speedlings and Lannen trays. Speedlings are most commonly used for grasses, herbs and saltbush, but have also been successfully used for all native plants in high rainfall areas (>800mm).
Forestry tubes are ideal for community plantings where lots of people will plant a few plants each, or in situations where you only want a few plants of each species. They are best planted with the Hamilton planter.
Healthy seedlings of sufficent size are crucial to successful tree planting. Seedlings need to have healthy roots that are ready to grow as soon as they come into contact with the soil, so as they can establish a permanent water supply and not be reliant on supplementary watering. The shoot should have healthy leaves that can begin to provide the energy the plant needs for growth through photosynthesis. The ratio of the shoot to the root is important. Too big a shoot:root ratio means the root system is unlikely to provide enough water to support the shoot and the plant will be top heavy. Too small a shoot:root ratio and the leaves will not be able to provide enough energy for the roots to grow. Ideally a shoot:root ratio between 1 and 3 is ideal. Roots should not be circling in the pot. Plants with circling roots can "strangle" themselves in the field many years after planting, and growth is nearly always slower. Roots should also not be protruding from the sides or base of the pot. Modern nursery practices encourage air-pruning of roots as soon as they protrude from the pot. Any protruding roots should be cut off with a clean pair of secateurs before planting. Avoid plants with very thick roots protruding.
Seedlings should be hardened off to suit the conditions they will be established into. Nurseries provide an artificially benign environment for young plants to grow in. Unless plants are hardened, they will suffer transplant shock and are likely to die. Heat and frost are the conditions that plants must be most prepared for. Before planting, seedlings should be stored in the open, where they will experience temperatures closer to what they will experience after planting. In very frosty conditions, a light shadecloth cover should be placed over the plants at night. In hot weather, the watering in the nursery must be gradually reduced for a few weeks prior to planting. Frost hardy seedlings (particularly eucalypts) are likely to have a pink tinge on leaves that are exposed to the sun. This is not a sign of poor quality plants, although patches of pink on all leaves can indicate phosphorous deficiency.
When seedlings are grown close together, as in trays or tubes stored close together, they usually only have leaves on the top third of the shoot. This will not affect growth if the plants are not too tall or if the shoot:root ratio is less than 3. Tall seedlings with only a few leaves at the top should be avoided.
You can get some more ideas on specifications for nursery stock from the Seedling Quality article on the WA government Nature Base website.
For large numbers of plants (>200) most nurseries prefer to receive orders in advance. This ensures that they can grow the mix of species, to the specifications and timing of the client. It takes time to collect seed, propagate and grow the seed and harden the seedlings. Try to place your orders 9-12 months in advance of planting. You should expect to have to pay a small deposit for large orders. You should get to know your local tree nurseries - find out what pots they use, how much they charge, which species they can grow and whether they can deliver.
Most species can be grown to a sufficient size in one season for transplanting, but others may take two or more years. Xanthorrhoea, Callitris and Bursaria can take 2 years to reach sufficient size. Some species are notoriously difficult to germinate and you and the nursery propagator may need to do some research to find the best method for germination. The Floradata database is a good place to start on the Florabank website or see the germination references under "Resources and References".
If you want to use seed from a particular provenance, you will need to give the nursery sufficient notice to be able to collect it, or you may be able to supply the seed yourself. Local nurseries will usually have a range of seedlots for each of the species commonly used in revegetation in the region.
Once seedlings are moved from the nursery to the planting site, careful handling is essential to ensure that they stay in optimum condition. If seedlings are to be held at the planting site before or during planting, they should be stored in a temporary shadehouse, or at least in the shade of a tree. If the planting takes a few days, or if the weather is hot, be prepared to water the seedlings frequently.
To increase the efficiency of planting, planters should be able to carry a number of seedlings as they walk. There are tools available to help carry seedlings. Belt mounted trays can carry seedlings that have been removed from their trays or pots. These "kidney trays" can carry up to 100 Hiko or Lannen cells or 50 tubes. Trays (Hiko or Lannen or similar) can be carried whole on hooks held on the belt. A hook goes through the tray and the tray rests on a foam block in order to keep it upright. Planters can carry up to 4 trays this way. Separate shoulder harnesses are available for carrying stakes and tree guards, mulch mats or fertiliser. While it is common for a tree planter to carry fertiliser (particularly in forestry) it is not common practice for tree planters to apply tree guards in the same operation.
Once seedlings are removed from their tray or tube, they are extremely vulnerable to dessication and should be planted as quickly as possible.
In forestry, carbon-sink or large-scale biodiversity plantings, many trees need to be planted quickly. A well trained crew of 8 makes an efficient team and is usually more effective than using mechanical planters. A crew of 8 would have a supervisor who directs the whole operation and a "storeman" who ensures that the planters have sufficent plants, guards, stakes and fertiliser and who collects the discarded trays. The supervisor will usually assist with this role. The remaining six can all plant, then guard once they finish a row or section, or three can plant while three guard. Planting is hard work, so it is essential that planters are fit and well-equipped, and have access to protective clothing (boots, hats, sunglasses at a minimum), plenty of water and regular breaks. In order to plant efficiently and quickly, the planting operation must be well-planned. The supervisor should visit the site the day before planting to decide where to hold plants, where to store guards and stakes, which parts to plant at what time and where vehicles are able to go to deliver plants and collect empty trays. Also look for a shady tree for lunch and smoko!
Mechanical planters operate in a similar way to direct seeders. Usually tractor-drawn, they open a slot in the soil into which an operator drops a seedling. The planter then firms the soil around the seedlings with press wheels. Planters can also incorporate scalping for weed control, fertiliser application and watering. Mechanical planters require the soil to be well-prepared to a fine tilth in advance. Like team planting by hand, it is essential to manage the work flow to keep a steady supply of seedlings, fertiliser and water up to the machine. Planters can be hard on the operator who is constantly bending to drop the seedlings. However, they are much less physically hard than planting by hand. An efficiently running machine planter can establish up to 1000 plants per hour, using 3 or 4 people. They do not work well in rough, rocky or steep country. machine planting is best considered for large plantings >10,000 seedlings or for groups who want to get their annual tree establishment completed in a few days.Mechanical planters are available for hire through some landcare groups, Greening Australia (Victoria, NSW and WA) or you can engage a contractor with their own planter.
Specialised tools are available to use high pressure jets of water to prepare planting holes. A "spear" with a handle, attached to a firefighter pump, pushes water into the soil creating a deep hole and filling the soil profile with water. Usually one person prepares the holes, followed by another who plants the trees. This method has been used successfully to establish long-stemmed tubestock in river banks. In this method very tall seedlings are planted deeply into water -injected holes in the bank. The seedlings establish lots of roots and are much better able to hold on if there is a flood or a fast flow.
You will find lots of great information about tubestock planting on the Greening Australia website.
The Australian Journal Ecological Management and Restoration, often features articles and research on revegetation techniques.
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