Propagating Australian native plants from seed

The Myrtles  - ​eucalypts, callistemons, melaleucas, leptospermums and more. 
    
Part 2 - From seed to plants 
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Manna Gum (Eucalyptus viminalis) seed showing tan-brown chaff and larger black seeds

Let’s take a close look at the seed you’ve collected

If you tip a sample of your various types of Myrtle seeds onto a sheet of white paper, you will see that they vary in colour, size and shape.

Eucalyptus seed.
The contents of the eucalyptus fruit capsules has both fertile seed and infertile seed called chaff. The eucalypt seed is usually dark brown/black and sand grain sized. The smaller tan-brown granules are the chaff.

There is less seed than there is chaff but there is still a lot of seed.

For example:
1 gram of River Red Gum, E. camaldulensis seed has an average of 700 fertile seeds;
1 gram of Manna Gum, E. viminalis = 350 seeds;
1 gram of Yellow Box, E. melliodora = 350 seeds;
1 gram of Yellow Gum, E. leucoxylon = 230 seeds;
1 gram of Messmate, E. obliqua = 200 seeds.

Close relatives of the eucalypts are the bloodwoods or Corymbias:
Spotted Gum, Corymbia maculata. It has larger seeds in the fruit capsules = 100 seeds/g.
​They are easy to see and can be shaken directly into cells/tubes.
Scarlet Flowering Gum, C. ficifolia = 40 seeds/g. They are large enough to pick up with fingers or tweezers and sow directly into tubes

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Paperbark, Melaleuca spp. & Bottlebrush, Callistemon spp. seed

Paperbark seed. To distinguishing the seed from the chaff a magnifying glass is helpful

The contents of the Paperbark and Bottlebrush capsules is also a combination of seed and chaff, though it’s all much smaller.

​For example the Swamp Paperbark, Melaleuca ericifolia has very small ‘dust’ sized seed plus chaff.
Average number of seeds/gram = 1,500


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​Tea-tree, Leptospermum spp. seed

The Tea-tree capsules are full of fertile long narrow tan-brown seeds
Average number of seeds/gram = 500

Figure. Woolly Tea-tree, Leptospermum lanigerum seed under magnification.                                                                                                (Click on images to enlarge).                                                   

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When to sow

Freshly sown in a seedling tray. From left to right; River Red Gum, Drooping Sheoak, Yellow Box, Moonah

The warmer months of spring to late-summer (November – February) are ideal for sowing most native seed. This provides enough warmth for good germination and long sunny days for strong growth in tubes.

Allow 6-8 weeks for seedlings to mature in tubes. They will then ‘harden-off’ in the autumn months and be ready to plant in revegetation areas in the winter/spring.
The sowing of native seed is usually completed by  late February in southern Australia.

Nurseryman’s tip. The seed of most plants will germinate very well outside in the warm months. They are hardier than plants germinated in a green-house or under shade.
Choose a protected place in the garden that is convenient to water. 

A green-house covered with white shade-cloth to prevent overheating on hot days is also suitable.  This more controlled environment protects vulnerable small plants from birds, possums, heavy rain and hail. 

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Labels - what to record

The same seedling tray as shown above with well spaced germination (4 weeks later)

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​Write on your labels the plant species name, where collected, the date sown and the quantity sown . Place the labels in your trays as a guide to where to sow the seed.
 
​ The seed is covered with a thin layer of seed raising mix

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Seed sowing

Seed can be sown into;

• Seedling trays.  Later transplant into tubes when the plants are large enough to handle
• Directly into tubes.  Thin to one plant/tube and hardened-off for planting
• Directly into the soil to cut out the intermediate steps

Damping-off fungus in a tray of melaleuca sown too densely. The bottom of the image the plants were just as dense but have all died

​Nurseryman’s tip
Try to avoid a germination so dense that it looks like the grass on your back lawn. This is more likely to happen with the very fine melaleuca and callistemon seeds. 

If this does happen it’s better to thin seedlings early so that there is clear space between them. 

Very dense sowings are likely to develop 'damping-off fungus' which can wipe out your whole tray. If this happens you’ll need a fungicide to control the spread of the fungus - it starts to get complicated.

Make an appropriate note in your seed sowing notebook for next year to cut back on the seed volume sown. 

This problem can be avoided by first doing a test sowing. Try 1/4 teaspoon for larger myrtle seeds and 1/16 tsp for the very fine tea-tree and melaleuca seeds.

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Tubes

Ideal mature tree heights in Hiko cells, Lannen cells and forestry tubes. (Ref. Recreating the Country, a blueprint for the design of sustainable landscapes)

The same potting mix can be used (without sieving) in tubes for transplanting natives. I usually include 20% coir-peat which keeps it moist longer and 10% basalt dust for minerals. At this stage slow release fertiliser can be added either at the time of mixing or to the top of the tube at the time of transplanting. 

The trick is to choose the correct nutricote or osmocote slow release fertiliser;

Choose a formula designed for natives – it will be low in phosphorus (P) and relatively low in nitrogen (N) and potassium (K). You may also need micro-nutrients.

If you add basalt dust you won’t need micro-nutrients. This is because basalt is a mineral rich volcanic rock. When it is finely ground into a sand grade called 'dust' it can be used to enrich soils or  potting mixes.

Avoid using garden soil in potting mixes because it will introduce lots of weeds

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Seed can be directly sown into tubes or ‘pricked-out’ of seedling trays.

Hiko cells with holes ready for sowing seed. These germinate well in an outside environment during the warmer months

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Direct sowing into tubes is better suited to larger seeds that are easily seen and counted like the Bloodwoods described above under the ‘eucalyptus seed’.

The usual practice is to make a small hole with a dibber-stick (see below) for the seed or sow on top and cover with potting mix. The seed is shaken in with a seed dispenser or the larger seeds can be planted with tweezers. 

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Pricking-out seedlings takes some patience and some practice. If the seedlings are small at the time of transplanting, the process is much faster and less skill is required.

How its done

Smaller seedlings are much easier to plant, are less stressed and just as hardy

1. Find a cool shady area to work, inside or outside. You can work standing or sitting though you need to be comfortable. Be aware of back soreness – you may need to raise or lower the tray to a more ergonomic height
2. Make yourself a dibber-stick with a point about the size of a pencil. Long tweezers can also be used, though the planting technique is slightly different.
3. Dibber your holes in advance (3-4cm deep and 1-2cm wide) and drop in a pinch of fertiliser if not in the mix
4. Carefully lift a group of seedlings from the seedling tray and divide them into single plants
5. Pick up a plant by the leaves and dip it into a cup of clean water to draw its fine roots together. Holding plants too firmly by the stem can damage a small seedling.
6. Pinch out/cut the roots with your finger nails to about 2-3 cm length. This important step minimises kinking of the roots called J-rooting.
7. Carefully plant the seedling keeping the roots straight. If using tweezers, clamp the base of the roots with the tweezers and guide them deep into the dibbled hole
8. Push the potting mix around the plant from the sides with your dibber-stick or tweezers
9. Water in with a soft-flow when the tray is complete, to remove air pockets and settle the potting mix around the roots
10. Keep in a shady place for a few days until the plants are all standing to attention.
11. Grow them on in a sunny location that is protected from the wind. Windy days can be more drying than hot still days.
12. Water daily (twice daily on hot days). On hot and windy days inspect the plants regularly and water when necessary. If trays do dry out and the plants look stressed, sit your trays in 50 mm deep tub of water for 30 minutes to thoroughly re-hydrate them. This is much more effective than watering from the top. It takes multiple waterings from the top to rehydrate dry plants.

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​Nurseryman’s tip
Native seedlings will toughen-up when they run out of fertiliser. Knowing this you can prepare them for planting-out in exposed areas. Add your slow release fertiliser to strategically run out in early autumn so your plants start to harden off before the extreme cold of winter

​For example, plants fertilised with 70 day native nutricote in early February will run-out of food by mid-April (about 7o days after the fertiliser was added). Their leaves will harden and their growth will slow. They will be better prepared to survive the winter and the exposed conditions in the garden or the back paddock when planted out
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A Manna Gum, one year after planting

 Some awesome thoughts

​A small seed carries the complex coding to grow a living organism with roots, stems, leaves, flowers and fruit that at a casual glance appears identical to its parent. Surprisingly the euclaypt species that produce the smallest seed grow into the biggest trees. "From little things .......

These new plants also carry with them a millennia of adaptations to soil chemistry, topography, variable weather and seasonal changes in climate.

Plants provide food and habitat for Australian wildlife, oxygenate the air we breathe and provide us with outstanding beauty, shade and wind shelter.

Through some simple steps we can collect native seed and grow beautiful trees, shrubs, herbs and grasses that can be planted for the benefit of all. 

What a privilege it is to be part of something so awesome. 

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