Germination temperatures for Xanthorrhoea johnsonii seeds from south-east Queensland ranges from 13 - 31 degrees C, with optimal temperature being around 18 - 27 degrees C. Below 9 degrees C and above 35 degrees C germination does not seem to happen.
Seeds generally germinate on average in about 12 - 14 days, with heavier or larger seeds germination at a higher percentage rate than lighter or smaller seeds.
Another study also found that seeds collected from the top third of the spike had lower germination rates than from the middle third. Seeds burried under soil germinated better than those just sown on top with light inhibiting germination. Many of the X. johnsonii seeds tend to stay dormant for about 10 weeks before sprouting with some seedlings only showing up about 18 months after sowing, demonstrating the dormancy capability of these seeds.
Seeds can remain viable anywhere between 3 - 54 months depending on storage and treatment. You want to make sure seeds are kept dry with paper bags or envelopes being a good option.
