Fir cones/pine cones

[Haj]

Hi, how come the fir cones we painted in the garden yesterday have suddenly close up tightly?

Thery were all splayed and open yesterday and we painted inside them. They've been left out inthe rain and are now closed. I could understand this if they were still attached to the tree, but they've been unattached for weeks now and in my sons room waiting to be painted.

He asked me the above and I haven't got a clue what to say!

Any ideas?

[gen2]

Haj, As the cells on the outside absorb water, they swell and force the cone shut.  If the comes are left in the sun to dry out, the cells will shrink again and the cone will open once more.

The cone does not have to be living and growing on the plant for this to happen, it is a natural property of the cells.  I am sure most people have experienced something similar such as a wooden cellar door that sticks when it is wet and the wood has swollen, but opens easily again when it dries out.  The only difference in the fir cone is that the water is absorbed most easily on the outside and the uneven swelling causes it to bend and close up.

Incidentally, fir cones can be used to predict the weather by noting how open or closed they are.  The more they are closed, the more humid the air (and hence the greater chance of rain).

[Haj]

Wow, that's really interesting, thanks for the response.

[Clanad]

Interestingly, in the western U.S., some varieties of fir, especially Douglas Fir and Lodgepole Pine propagate best when subjected to forest fires.  It seems to take a fairly intense heat to force the cones open.  When they do open, they do it suddenly and the seeds are scattered rather just dropped... I suspect it has to do with quickened drying of the covering as described by gen2, rather than a gradual drying...