INFORMATION NOTE 3: PROPAGATION & GROWING
TREAT’s replanting and restoration efforts are focussed on the Atherton and Evelyn Tablelands, in the Wet Tropics of Far North Queensland. The predominant vegetation type here is rainforest, although there are also areas of wet sclerophyll and heath. These notes are written for restoration of rainforest habitat by TREAT members on the Tablelands.
For further information download: ‘Repairing the rainforest’ (2013) 2nd ed by S Goosem and N Tucker. WTMA & Biotropica.
1. SEED SOURCE
(See INFORMATION NOTE 2: SPECIES SELECTION)
Collect seed from your local area and forest type. For best results, match your Regional Ecosystem – so that the climate (rainfall), soil type and altitude will be similar to that of your planting site. Your will a map and description of Regional Ecosystems at https://www.qld.gov.au/environment/plants-animals/plants/ecosystems.
Get advice from TREAT, the TRC nursery or specialist consultants based on the Tablelands.
Collect seed from rainforest remnants on private land (ask permission first). Collection from National Parks is prohibited. Permits can be obtained for collection from Forestry land.
2. A MAP AND A DIARY
Rainforest species flower and fruit at different times of the year. The fruit collection diary in the TREAT newsletter is a good place to look to find out what fruits when in the Tablelands area. The Coopers’ book and the Rainforest Key are also useful.
QPWS staff record flowering and fruit development times so that they know at what stage fruit can be harvested – too early and seed is not viable, too late and the fruit has been eaten or blown away in the wind or is rotting on the ground. Monitor potential seed trees regularly so that you can harvest fruit before it is eaten or dispersed. Fruit of some species is ready for harvest three months after flowering whereas Flindersia brayleyana, for example, starts to flower shortly before the seed developing from the previous year is ready to be released.
You can use a smart phone to record location data when you take photos of source trees. You can use this to construct a map of harvest sites.
3. SEED COLLECTION
Fruit can be divided into two categories. Fruit that splits (dehisces) to release the seed is usually harvested just before it splits and then stored in paper bags or spread on seed trays to allow the fruit to split. Fleshy fruit needs to be monitored so that it can be collected before it is eaten. Seed will usually germinate from slightly unripe fruit.
Wherever possible harvest from fruit the tree rather than the ground. Fruit on the ground is often damaged by rodent or insect predation or infected with fungi.
Keep each collection separate and label with location, date and species name. Zip-lock bags are convenient for small fleshy fruit and paper bags or envelopes for dry fruit. Photograph any fruit that you can’t identify. Foliage samples will help with identification.
4. SEED PROCESSING
Most rainforest seed cannot be stored so you will need to be ready to process and plant the seed. For some species, seed must be planted immediately. Most species benefit from some form of processing, where the seed is removed from the fleshy fruit or woody pod or capsule. There are a few species (such as ) that grow better if sowing is delayed until after the spring equinox or warmer weather.
5. TREATMENT
Hard-seeded legumes (such as ) benefit from scarification with a file or knife. Alternatively, pour boiling water over seed. This helps break down the hard seed covering. species also have a hard seed covering that inhibits germination. Pour boiling water over the seeds and leave them in the water for three to five weeks.
There are too many different species and types of seed to describe all of them here, but there are some general principles that will assist in improving germination rate and speed. Remove any flesh or appendages that will rot in the growing medium. As a general rule, try to mimic what will happen with natural dispersal.
a. Seed enclosed in a hard shell:
Aleurites rockinghamensis (Candlenut), Elaeocarpus (Quandong) species , Athertonia diversifolia (Atherton nut)
Remove any flesh covering the hard shell. Crack the shell to allow the seed to absorb water and the root system to emerge. Using a hammer will pulverise the seed — the best technique is to put the shell longways (putting the end where the fruit was attached to the tree at one end) in a vice and turn the handle until you hear a crack. Remove the seed (kernel) from the cracked shell.
b. Seeds enclosed in a fleshy covering:
Examples: Syzygium (Satinash) species, Acronychia
Flesh needs to be removed for many reasons. In nature seeds would be cleaned by birds or bats that ingest the flesh and eject the seed from either end. Flesh in the seed tray is infested by insects or pathogens that damage the seed. Flesh also often contains germination inhibitors.
Removing flesh is often easier if fruit is soaked first or allowed to sweat. Soaking seed also helps kill any insect larvae in the seed.
c. Fleshy fruit with tiny seeds:
Examples: Ficus (Fig) species and Nauclea orientalis (Leichhardt tree)
Allow fruit to dry and crumble into small pieces. Alternatively, collect bat spats (mouthings).
d. Seeds enclosed in a woody capsule or winged seeds:
Examples: Alstonia scholaris (Milky Pine), Argyrodendron (Tulip Oaks) species, Melaleuca (Bottlebrush) species, Darlingia (Silky Oak), Flindersia (Malples, Silkwoods) species , Xanthostemon (Penda)
Collect the woody fruits when they are still slightly green — otherwise the seed will shed when you try to pick them. Place the fruits on clean paper in place that is warm and dry (but not windy). Fruit should start to split in 1 to 4 days and seed will fall out of the capsule. If the fruit doesn’t split it may be too immature – go back and collect again.
A well-lit environment is essential for germinating seed in this group and a soggy medium will cause the seed to rot. Note that many of these species have packing material or spacers that protect the seed. Learn to recognise what is seed and what is packing — plant the seed but not the packaging.
Germination is usually rapid (less than 30 days) so if nothing has happened in this time discard the tray and start again.
When sowing winged seed, arrange the seeds upright (not flat), burying about a third of the seed.
e. Seeds naked on cone scales (conifers):
Examples: Agathis robusta (Kauri), Araucaria cunninghamii (Hoop pine)
Seeds (pine nuts) are attached to flattened wedge shaped wings which lie between the cone scales. Cones can be collected as they fall (race the rats for the tasty pine nuts) and allowed to open as for group (d). Seed should be sown immediately, otherwise the seeds shrivel and die. Araucaria cunninghamiana and Agathis robusta have reliable germination but Agathis atropurpurea (Black Kauri) and Agathis microstachya (Bull Kauri) frequently have low viability.
f. Pioneer:
Examples: Acacia (Wattle) species, Homolanthus novoguineensis (Bleeding Heart), Macaranga, Alphitonia (Sarsparilla).species
Seeds of this group are usually small and enclosed in a simple capsule. Pioneer species have seed that is able to wait until conditions are right for germination and this means that they often have enforced dormancy and specific triggers for germination. Without being able to replicate these triggers, germination is often sporadic and erratic. It can be either very successful or a total failure depending on whether requirements are satisfied.
Treatment with boiling water is usually successful for and a species. Remove the pods or woody coverings from the seed. Pour boiling water over the seeds. For , leave seed in the water for 2 to 3 weeks.
Remove seed of or from the capsule and sow immediately. They usually germinate in 14 to 40 days. If nothing has happened after 3 months throw the contents of the seed tray under a tree. This often stimulates the whole tray of seed to germinate.
g. Very large seeds:
Examples: Castanospermum australe (Black bean), Endiandra palmerstonii (Black Walnut), Syzygium gustavioides (Grey Satinash), Hicksbeachia pilosa (Red Bauple Nut)
These species typically develop extensive root systems before a shoot appears above ground, which makes it difficult to pot them up from the seed tray without damaging their root system. They also tend to dry out quickly because they quickly grow too big for the tray. It is also inefficient having to pot individuals out of a tray, and disruptive to the other seeds. Therefore, these seeds are sown directly and individually in forestry tubes. Castanospermum australe should be sown with the ’split’ side facing up. Bunya pine should be won with the sharp end pointing into the soil. Cerbera inflata, Cycas media are usually sown into seedling trays because they are recalcitrant.
6. LABEL
Keep seeds of different species separate when sowing. Prepare the sowing label before you sow the seed — that way you won’t forget. Label with name, seed sowing date and collection information.
7. SEED-RAISING MEDIUM
Use a well-drained mix that holds sufficient moisture to keep seedlings alive between watering. A coarse open mix is best because seeds and seedlings are vulnerable to fungal infections. At the TREAT nursery we use:
50 % coarse (sharp) sand – do not use fine builders’ sand or beach sand
50 % composted pine bark.
Note that seed raising mix does not contain fertilizer.
8. SOWING
Seed trays are between 60 and 100mm deep. These are preferred to pots because the shallower root system means that seedlings are subject to less stress when they are potted up.
Fill the seed tray to within 1cm of the top. Gently tamp down the surface to get rid of lumps and bumps or air pockets.
The sowing depth and density will depend on seed size and viability. Sprinkle seed evenly. You can mix very fine seed with dry sand to get a more even spread. Lightly sprinkle volcanic scoria (quincan) or seed mix over the top to the point where the seed starts to disappear.
For large seed (more than about 30 mm), place directly in tubes or tray. Think about how the seed would fall or roll naturally. Align seed so that roots and shoots can emerge from either side (in other words, don’t plant the seed upside down). Push three quarters of the seed into the seed raising mix.
Immediately water the seedling tray — gently — so as to settle the mix around the seeds but without washing them about. Always use a misting or fine droplet sprinkler head. Allow the water to soak in and then repeat.
9. CARE
Keep the seed mix moist but not wet during the germination period. Monitor. Water according to need (poke a finger into the seed tray – does it feel damp or dry?). On hot sunny days water more frequently than during cool overcast humid weather. Growing seedlings need more water. If the trays are kept saturated seed and seedlings rot. Too little water and they dry out. Hand water with a soft rose or spray nozzle that doesn’t disturb seed.
10. HOUSING
Keep seedling trays in an airy and well-lit place but not in direct sunlight or direct rain. Trays need to be above splash height from the ground (and toads and disease) and away from sources of weed seeds. Housing also needs to be rodent-proof — otherwise you are providing a smorgasbord.
11. DIBBLING
Most rainforest species can be stored as germinated seeds in seed trays. (The exceptions are seedlings from large-fruited species where germinated seed inhibits germination of other seed and quickly becomes pot-bound). When more individuals are needed (you need to allow for growing time) seeds are ‘pricked’ or ‘dibbled’ out and potted up from the seed tray.
Dibbling out involves gently prying out a small handful of seedlings at a time, using a dibbling tool such as a knife or chopstick, avoiding pulling or tearing tiny fragile root systems. Start from the corner of the seed tray. Removing seedlings places a great deal of stress on them and needs to be done as gently as possible and in a place away from drying draughts or sunlight. Use moist potting mix or paper towel to cover the roots of seedlings waiting to be potted up.
Seedlings are ready to be dibbled when they have four adult leaves — generally between 20 and 60 mm high — but the height of seedlings depends mostly on seed size. Seedlings from species with large seeds (such as Cerbera and Aleurites) may reach 300 mm before they have leaves. Seedlings from fig species and some Myrtaceae (Thaleropia and Melaleuca) are tiny.
To improve transplanting success, give the seedling tray a good watering the night before — even better, water with Seasol two weeks as well as the night before potting-on.
12. POTTING MIX FOR POTTING OR GROWING-ON
Growing medium for seedlings:
0.5 bucket cocopeat (or river sand)
4.5 buckets composted pine bark
200 – 250 ml (1 cup) of Osmocote Pro-Native slow release (10 – 14 month) fertilizer
3/4 cup of ‘Katek Supergrowth’ organic fertilizer
(If pH is below 4.5 add 0.5 cup dolomite)
Proteaceae mix
2.5 bucket cocopeat (or river sand)
2.5 buckets composted pine bark
200 – 250 ml (1 cup) of Osmocote Pro-Native slow release (10 – 14 month) fertilizer
1 cup of urea
Note that a combination of soil, straw and manure is not a recipe for potting mix but for making mud bricks.
13. POTTING-ON
Tubes or forestry tubes are the preferred containers. These allow a healthy root system to develop while using less potting mix and nursery space.
Before potting-on, make sure that the potting mix is moist to avoid moisture being drawn away from the plants’ roots. Place potting mix in the base of the tube (fill to about one fifth), settling it by gently tapping the tube on the bench. Hold the seedling by its leaves (pinching the stem bruises it and the seedling could die) and suspend it over the tube so that the root system is 1 cm below the rim of the pot. Continue holding the seedling and gently fill the tube with potting mix, alternating between sides so that the seedling remains in the centre and the roots do not curl upwards. Continue until the potting mix reaches the top of the potting mix. Firm up the potting mix by gently tapping the base of the tube on the potting bench. There should be about 1cm free at the top so that the tube can be watered. Avoid compacting the potting mix, since this will damage the root system.
Gently and softly water seedlings immediately after they are transplanted — use a watering can with a rose. Transfer to a shade-house or similarly sheltered location (out of direct sun and wind).
14. HARDENING OFF
Plants are ready for hardening when:
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There is new growth
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Leaves turn a darker, brighter green
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There are signs of root development at the base of the tube
Both will happen only after the root system has recovered. Most plants are ready for hardening after three to four weeks in the shade-house. If possible, move plants out of the shade-house during cloudy or overcast weather. Softer new leaves may discolour or burn a little in full sun, but the plant should recover.
Plants are grown in full sun so that they can adjust to these conditions before they are planted out. Plants should be grown on a level raised surface above water splash and toad height. This reduces the chances of weed infestation and water borne diseases. An aerated surface (such as mesh benches) encourages aerial pruning of roots. In these conditions, plants are at risk of drying out quickly, so attention to irrigation is critical.
In the TREAT nursery, plants are placed with other batches of the same provenance and organised according to regional ecosystem.
15. MAINTENANCE
Weeding
Keep plants weed free. Weeds compete for water, light, space and nutrients. They quickly produce seeds that spread to other parts of the nursery and to the planting site. At the same time remove fallen leaves and other debris from the surface of the potting mix that may impede irrigation.
Pests and diseases
Monitor for slugs or other pests.
Sizing
Plants benefit from sizing and trimming when they are on crowded nursery benches.
Grade in size so that larger seedlings do not shade out smaller ones. Size the entire batch of plants from shortest at the front to tallest to reduce competition and give all a chance to grow. Consolidation and pruning, if appropriate, should be carried out at the same time as sizing.
Pruning
Some species get too bushy, preventing water from reaching the tubes. These benefit from trimming lower leaves. Remove any unhealthy or yellowing leaves. Trim any roots growing out of the base of the tube with sharp, clean secateurs. Plants that get too top heavy have to be pruned back to the point where the stem stands upright. Most species benefit from tip pruning, to encourage plants to increase stem diameter rather than height. At least one (preferably two) active node with leaves should be left on the plant. Examples. Some species (list) do not like being pruned (list). Remember it is stem girth not height that determines resilience when planted out. PHOTO
Consolidation
Remove dead tubestock and any that are failing to thrive. Keep plants from one batch together – don’t mix provenance or species. Check that the identification label is legible and placed where it can be read but not dislodged.
16. IRRIGATION
The potting mix is well-drained so tubestock will need to be watered twice a day, more in hot or windy weather. In wet monsoonal weather watering may not be required. Watering in the early morning and late afternoon keeps plants hydrated. If you are hand watering, use a soft rose or spray nozzle on the hose or watering can. One full 10 litre watering can will water six trays of tubes. After watering, leave the tray for at least 2 minutes so that the water has a chance to soak in before repeating. If an irrigation system is used to water plants it will need to be carefully monitored to determine the appropriate run time according to weather conditions. Sufficient water should be supplied so that the growing medium is moist at both the top and bottom of the pot. Test by looking, feeling (put a finger in the mix at the top) and hefting – does the pot feel light? Overwatering is wasteful, causes runoff problems and leaches away fertilizer.
Be aware that leaves wilt if plants are too dry, but leaves will also wilt if plants have diseased root systems — these can be caused by waterlogged conditions. So, check the cause before watering.
17. PLANT SELECTION
Choose the healthiest stock for planting (with the greatest stem diameter). Soak in Seasol 24 hours before planting.