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How To Get Australian Native Seeds to Sprout
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The seed of most native tree species sprouts readily when put in a warm moist environment. These do not need any treatment before sowing. But fresh seed of some species has built-in mechanisms to delay germination for several months or even for many years, and such seed is said to be dormant. In the wild, this characteristic can aid survival, but before such seed is sown, it must be treated to deal with the dormancy. Seeds with hard coats Some native legumes produce seed with a hard coat - a seed feels hard if pressed. These legumes include many of the wattles and the Albizia and Cassia genera. Such a hard seed coat must be broken by hand or in boiling water before the seed is sown. The coat of each hard-coated seed can be pricked, chipped, nicked or filed - this method is called scarification. Use either a sharp knife, nail clippers, a small file or nail file, a big needle mounted in a wooden handle, or sandpaper. Scarification is easier with larger seed and, because it takes time, it is used when seed numbers are small or when the seed is scarce or valuable. A good way to learn this technique is to treat and germinate some large common seeds. First, find the scar on the seed coat where it once joined the pod - this scar is often a tiny light-coloured spot at one end of the seed - but do not cut or damage this end as this is where the root emerges. Treat the other end of the seed a bit to one side - the seed's shoulder. Cut, prick or rub away a small piece of coat (no more than 1 mm square) to expose the white contents. If you can just see white through the coat, the treatment is right. Accidental damage to a small part of the seed's contents will not prevent germination, but do as little damage as possible. The treated seed may be soaked in water for 24 hours and then sown into a prepared germination tray, or may be sown immediately into the tray. Larger seed is often sown directly into individual containers - about 2 or 3 seeds per container. Boiling-water treatment Soaking the seed for one minute in boiling water will break the dormancy in a wide range of hard-coated seed - the method perhaps imitates the effect of a bushfire. It is a quick and easy method, and large numbers of seeds can be treated with a saucepan, a kitchen stove and a kitchen sieve or strainer. Boil some clean water equal to about ten times the volume of the seed. Then pour in the seed and boil it for just one minute - measure the time accurately. Take the saucepan off the stove and let the seed remain in the slowly-cooling water for about three hours, then pour off the water and sow the seed. Nearly all wattles have hard-coated seeds but a few wattle species (and possibly a few species from other genera) produce seed with semi-hard or soft coats. If pressed, these seed often feel softer than the hard-coated ones. For example brigalow seed (Acacia harpophylla) has a soft coat, and eumong seed (Acacia stenophylla) has a semi-hard coat. Boiling water will kill all seed with soft or semi-hard coats. Wattle seed with a soft coat should be sown without any treatment. Seed with a semi-hard coat can be soaked in hot water (90°C) for one minute only. Measure temperature and time accurately. If you do not have a thermometer, bring a litre of water to the boil, then let it stand off the stove for a timed one minute forty seconds - then add the semi-hard seed and leave to soak for one minute. If you do not know whether certain seed will survive boiling water treatment, test a sample first. Cold-moist treatment Seed dormancy in some tree species - especially ones from areas with cold snowy winters - can be broken if the moist seed is chilled in a refrigerator. Many of the eucalypts native to the Mount Kosciusko region require such treatment. Sow the seed on a moist sowing mix in a germination tray, then cover the tray with a lid or a plastic sheet or put the tray in a plastic bag - the covering reduces drying. Place the tray in the bottom of a refrigerator at about 1° to 4° C and leave it for the required number of weeks. But check occasionally to make sure the sowing mixistays moist, and re-moisten it if necessary. Species Weeks in refrigerator (n = Necessary r = Recommended)
Next, put the tray in a warm sheltered place, and germination should begin within three to five days. This method is known as cold-moist stratification. It probably imitates the seeds lying on the ground dormant under snow in winter and germinating in spring after the snow melts. |
  
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