Tagasaste produces a hard coated seed and should be heat treated if a reasonably uniform germination is desired or required, as is usually the case for any commercial planting. This hard coat is actually the way that the plant protects itself from shooting its last bolt at the wrong time in the survival stakes. There will always be some seed from every year that will take a longer time to germinate, ensuring that deceitful weather conditions do not trigger germination. Then follow with a dry period that will kill the young seedlings before they have a chance to get a grip deep, into the earth from which they might take succour. To circumvent this situation, softening the seed coat will allow all the seed to germinate uniformly.
The most effective way to treat the seed, is to place the seed into a container, and pour boiling water over it, allowing it to soak overnight. The volume of water should be at least twice as much as the seed being treated, as the water is absorbed by the seed once the hard coat has been softened, making it double in size. Any seeds that don't swell, can be safely assumed to be unviable, and removed, though this isn't necessarily the case or required in most situations. Some seed which has had its coat breached by insect attack, may be killed by this process, but these would are generally few in number.
Another method, actually boiling the seed for 60 seconds certainly kills many more seeds. Smoke, which has been used to activate Australian native seeds with a hard coat, has not been trialled but might also deliver the desired result. The first method described here has been found to be very successful, with a 90% plus germination rate with our own seed, and we have stayed with this successful formula.
The soaked seed should then be strained into a colander or sieve, and washed while it is thus contained in or under clean, cold water to remove any growth inhibitors that may still remain. At this stage the seed is fragile, so strong jets of water or vigorous agitation should be avoided. Just agitating the seed in a bucket of water will suffice to wash it effectively.
The washed seed can then be inoculated with the Tagasaste root bacteria, which will produce the nitrogen storing nodules on the roots of the plants. A mixture of gum Arabic, or sugar water, the nodule bacteria and Tagasaste seed can be combined and mixed thoroughly, but gently. The gum Arabic or sugared syrup will assist in adhering the bacteria to the treated seed and once this has been done, the coated seed can then be spread onto newspaper to dry.
The seed should be sown as soon as possible after it is dry, to ensure that the inoculum is still alive. There is a school of thought that suggests the seed can be stored for a fortnight after the above treatment, but experience shows this is to long. A week would be the maximum time to store the inoculated seed, however, the less time treated seed is stored, the fresher is the seed and the bacteria and the better it will be. Once the seed has been activated by this procedure it is ready to germinate, and it is not going to benefit from delay before planting.
If conditions, or circumstance dictates, seed can be sown without first heat treating it. The seed will crack its own coat when the conditions are right. Then it can be inoculated by watering the area with the bacteria in a slurry. This method will mean an infrequent and uneven germination over a long period, even years, which might not be desirable. After 12 to 18 months, there will be some seed still germinating, but they will be few, and the earlier seedlings will be well established and appear reasonably uniform after three years.
Ants love the seed, after treatment or just as they are expelled from the pod by the tree. If ants are a considerable, vexatious problem the seed can be coated in clay. The treated seed can be coated before drying by gently moving it over a tray while dry crushed clay is dusted over it, thus encapsulating it in a protective, environmental friendly disguise.
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