Virtual Museum of Canada
Jardin botanique de Montréal 
Centre for Forest Research

Biding their time

Jack pines are even more protective of their offspring than oaks. Their branches hold onto the female cones – which close again after pollination, trapping the seeds inside. Why? Because the trees are waiting to burst into flames! And very patiently waiting, too: after twenty years, half of the seeds are still viable, and some even survive to age fifty!

Jack pines grow in an environment where there are many forest fires. When part of the forest burns, the soil is naturally fertilized by the ashes. Any seedlings that then sprout will have fewer competitors. So it's just the right moment for the female cones to open and release their seeds.

Photomontage of jack pine (Pinus banksiana) cones, at different maturity stages
Pinus banksiana
© Jardin botanique de Montréal (Gilles Murray)
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The female cones, which are as hard as rock, are covered in a layer of resin that seals the scales closed after pollination. During a forest fire, the resin melts, and the scales open like flowers. A few days later, after cooling off, the cone releases the seeds. Otherwise, they'd drop straight right into the fire – and that would be a real waste!