Issue Number #31
Issue Date Autumn 2005
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Title Cool Season Plants
Author Anna Povey

Now that there has been some cooler weather, the banksia seeds that I sowed months ago have begun a burst of germination. Sometimes a few seeds will germinate in spring, but most wait till autumn. When I look banksias up in my book ("Growing Australian Native Plants from Seed" by Murray Ralph), it says that high temperatures at the time of sowing may induce dormancy in some species, such as our own B. marginata, and that stratification (cold treatment) for 8-10 weeks can improve germination. Of course, you could use a shadehouse or some other means of avoiding high temperatures, and you could put them in a punnet in the fridge for a while (stratification). Or you could try sowing them now!

Actually a number of species prefer autumn sowings. Many lilies (such as chocolate lily and vanilla lily, and also trigger plants), Bursaria (fresh seed), Banksia, Brunonia, Callitris, Linum, and Myoporum are some that I have found (or read) do better sown in autumn. Some eucalypts (eg. E.pauciflora and E.amygdalina) also like a bit of cold before they germinate.

Some of these cold-loving species seem to germinate and grow through the cold weather, others like cold followed by warmth to germinate. So some of them may not germinate till spring, but they need the cold first. You can experiment with stratification, or simply do it the normal way outside and wait for something to happen. Stratification involves sowing the seeds on a punnet/seed tray, moistening the mix, placing in a plastic bag to reduce drying, then leaving in a fridge for 2-8 weeks. Make sure they haven't dried out. After the allotted time (books may guide you), bring out to the warmth, remove the plastic bag and keep moist and in the daylight.

Billardiera and Clematis often seem to germinate after some cold, but this is usually after 6-12 months in my experience, so I think there is just a period of time they have to sit there. I have tried autumn sowing clematis, but it still took over 6 months. Both of these seem to have a good germination rate once they get going. (Always assuming you had good seed in the first place).

By the way I have tried Milkmaids, Burchardia umbellata, a couple of times, sowing in autumn as this is a lily. They always germinate well for me, but (just as the book describes) they fail to thrive. No matter what I do, the seedlings stay little and spindly and ultimately die. Perhaps in nature they rely on some micro-organisms, but my efforts to introduce these with some bush soil from around the parent Milkmaids didn't work. Other lilies have always gone well for me, particularly in autumn.

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