ArborGen Seed Orchard
ArborGen's seed orchard is part of the process of producing superior pine tree varieties
Pinus radiata (“Radiata pine”), a native of California, was introduced into New Zealand in the 1850’s. It is New Zealand’s most important plantation forest species and represents close to 90% of the approximately 1.7 million hectares of such forest, in New Zealand.
Owners of commercial forest plantations want trees that grow quickly, produce more wood per hectare, are uniform, have good wood properties (such as easier to process) and are disease resistant.
Radiata pine tree improvement programmes started in NZ in the 1950’s, and tree breeding and improvement programmes continue to this day. Initially, good trees were visually selected from the production forests. After testing the progeny of these superior trees, the best performers were grafted and planted out into ‘seed orchards’ for the production of superior quality pine seed.
Seed harvested from these first generation orchards was called open pollinated (O.P.) seed. An open-pollinated tree grows from seed from a cross between a known, superior quality mother tree and a random father tree from a seed orchard of known superior genetics. Superior quality open pollinated seed is still widely used in the NZ market.
A major “jump” in tree improvement was made in the 1980’s with the development of control pollinated (C.P.) orchards and seed. In control pollination, flowers are isolated in pollination bags and selected pollen is injected into these bags. In this way, both parents are known superior quality trees.
Higher trait ratings generally mean better quality. Most trees currently being harvested in NZ that were planted around 30 years ago would average out at 14 – 17 on the GF scale. Trees that are being planted in New Zealand now typically range from GF 19 to GF plus-28. This represents substantial levels of improvement, tree quality and better outcomes for forest owners.
New improved parents are constantly being selected from genetic trials set out in forests and these then replace some of the lower ranked parents in each orchard.
Clones or varietals represent the next level of genetic improvement after OP and CP seed production. Varietals are the very best individual trees selected from trials. Millions of genetically identical trees can be produced using laboratory processes which use embryos to produce seedlings that are grown by standard nursery production methods. Material from the very best trees can be stored for many years if required.
ArborGen’s 15ha Awatere seed orchard is near the coast because this promotes good flowering. It contains 20,000 grafted trees, representing 60 parents, all of which are the very best selections out of the 4430 parents currently under test in NZ by the Radiata Pine Breeding Company (RPBC).
The orchard now also includes varietals as parent trees. Varietals are the “best of the best” individual trees selected and produced by ArborGen.
The orchard parents are selected for their wood traits:
- Volume (quantity of wood produced by the tree)
- Straightness (the straighter the tree, the easier to process at the sawmill)
- Branching habit (size and spacing of branches is important for the end use of the tree)
- Dothistroma resistance (a needle disease that can cause reduced growth in pine trees)
- Density (an important indicator of wood quality, including timber strength and stiffness)
The orchard was originally set up in 1995 by Carter Holt Harvey Forests, later the nursery business was merged with Fletcher Challenge Forests, and
ArborGen took over in 2004.
In the centre of the property is an office, seed extraction area, and cone storage facility. Four staff are employed full time.
Long term planning is required for optimal orchard composition. Cuttings are taken from mature trees of selected new parents and these are grafted onto rootstock at a nursery. A year later these grafted cuttings are planted at the seed orchard. As the cuttings mature they will start flowering at an early age but only become usefully productive in the third year after planting.
Pine cones are harvested two and a half years after pollination, and the seed is then extracted and ready for planting in the nurseries.
After seed sowing, depending on the location of the nursery, it takes 12 to 24 months for seedlings to grow to a size where they can be lifted and sent to the forest for planting.
It effectively takes seven to eight years after a parent is selected for the whole process to occur and a seedling to be produced and planted.
The orchard is laid out in rows and blocks, and all parents are carefully mapped and labelled. Any pollen that is collected must be similarly carefully tracked and labelled during drying and storage. The orchard is irrigated and regularly fertilised to optimize seed production.
Before pollination all the female flowers are enclosed in bags to prevent pollination by wild pollen. About 70,000 bags are put up and taken down each year.
The busiest time of the year in the seed orchard is from June to September when pollination and pollen collection is carried out. Great care is required in applying the right pollen to the right parent at the right time. This is definitely a job for careful and conscientious people. A dedicated group of 15, many of whom return year after year, are employed as casual staff to help the manager and his permanent team of four.
Pollen is collected, dried and normally cold stored ready for use next season, and it is viability-tested before application.
Cones are harvested in November and December before they dry out completely because they don’t want the cones to open on the tree. The cones are stored under cover to dry and then seeds are extracted and processed from March to June.
Once cones are harvested, the trees are form pruned to between 1.5 and 2m high which allows easy access to the flowers for pollinating. It makes the job easier and more cost effective to do all the work from the ground.
Each tree carries at least two crops of cones so pruning requires careful judgement to ensure the crops remain but the new branches for the next crop of flowers are maximized. Pruned branches are chipped and mulched around the rows of trees.
ArborGen carries out trials aimed at increasing the amount of viable seeds/cone by correct pollen application, the use of appropriate pollen storage techniques and optimal types of pollination bags.
With high quality radiata seed fetching more than $3000/kg, the aim is to continuously improve operating procedures in the orchard and produce as many cones as possible.
For each kg of seed produced, at least 18,000 seedlings can be grown for forest planting.
“Our aim is to be self-sufficient in controlled pollinated seed. We don’t sell seed, rather we sell seedlings grown from our seed to bigger forestry companies. We produce around 40% of the radiata pine seedlings in the NZ market,” says Wayne Smith, ArborGen’s tree improvement manager.
It takes three years to get useful quantities of seed from the planted orchard trees, and another four to five years before the new crosses from our seed are planted in the forest. Then it’s another 30 years to harvest. “There’s a lot of forward planning required and long-term thinking.”
When the flowers start to appear in mid June to early July medical bags are put over them to isolate them from any other pollen flying around. Staff tie the bags over the branches with reusable cable ties.
Battery powered pollinators are then used. Pollen is collected off particular required parents, and this is dried and stored in little jars in a freezer for use in next year’s pollination season.
Come May/June a pollination plan is worked out with particular pollen parents, the right parents are combined to give the best quality seed.
Once flowering occurs, the bagged flowers are assessed and when receptive, using a little needle pollen is squirted into the bag, and it is spread around the three to five flowers in each bag.
In comparison there are some open pollinated seed orchards such as one recently set up at Napier where pollination of high quality parents occurs from a mix of pollen from other parents in the orchard.
The frozen pollen generally stores well for many years, but every year the pollen is tested for viability before using it. It has to be at least 80% viability before being used, most of it is into the 90%’s.
The trees are all labelled on the ground, and the pollen is all labelled and tracked. The pollen is dried in kilns and place into the freezers to store.
Pollination runs any time from mid-June, to the end of September. After that, the orchard goes into maintenance mode until November when the cones start to be harvested.
The cones have to be taken off the tree before they get too dry and start opening. Harvest runs through November and December, and the cones are stored under cover in a shed to dry out slowly.
Then the immediate priority is to start pruning trees. Branches carrying the old crop are removed, mulched, and fed back under the trees. Pruning in January and early February enables new branches to grow to hold the next crop of flowers.
After pruning, seed extraction starts. Before pollination we need to know the exact quantities of seed for each cross, so that we can start determining what seed mixes are needed for our customers’ crops that will be sown in our nurseries in September.
The cones are cracked in a kiln where they are held for eight hours at 55degC. All the boxes (1m square and 600mm high) are lined with gauze, and each box only contains a particular cross.
Each box is put on a tipper and the seed falls out onto a chute which runs into a large tumbler, which shakes the seed out.
Cones come out the other end, and they are distributed to the local community.
When all the clean seed is collected, it has to be de-winged in a kind of concrete mixer where fine water is sprayed onto it before going into an airblower to get rid of the dead seed and impurities.
Finally the seed is sized to removed all the small seeds. This results in a more even germination. The staff then do germination tests to check seed viability.
The seed orchard is also improved each year by replacing lower ranked parents with new, higher ranked selections. The replacements are grafts, with cuttings from older trees grafted onto standard rootstock. This ensures new trees will produce flowers sooner after establishment.
So the cuttings are taken from selected parents in July and sent to a nursery to be grafted by a specialist and grown for a year. In May the trees to be replaced are mulched, the ground cultivated and replacement grafts planted in June before pollination starts.
Pinus radiata is native to California and was first bought to NZ in the mid 1800s. There was a wide variation in growth and form of these trees so a genetic improvement programme started in the 1950s.
Initially foresters selected the biggest and straightest trees to breed from.
They took this seed and grew it in trials, from which they chose trees they wanted.
Initially the focus was on growth and form, and the open pollinated seed from these trees was ranked using the GF system with values from 1-19.
Then foresters became more interested in other attributes such as disease resistance and wood quality.
With the establishment of control pollinated seed orchards the GF Plus system was developed which rates seed on the traits of growth, straightness, branching habit, dothistroma resistance and wood density.
It is a relative scoring system from 1-40 with the better ranked parents currently around the 28-29 level.
The ranking system means customers can choose the best combination of traits to meet the needs of their forest sites and the log products they want to grow.