Helping Our Peninsula's Environment


Monterey Pine Cone Natural Opening Studies

By David Dilworth

Well known to residents living in and near Monterey pine forests is the widespread crackling from natural opening of Monterey pine cones on warm, dry summer afternoons. When the cones open, occasionally one can see seeds fluttering, or even raining, to the ground.

This can occur on calm summer and fall afternoons no warmer than 70 degrees F. (Vandevere) . On October 13, 2001 I led a group to listen to cones crackling open from native Monterey pine trees in Monterey's Huckleberry Hill area while the ground level temperature did not exceed 70 degrees F. The National Weather Service Station, operated about a mile inland of our observation site and outside the native forest, recorded a high temperature of 86 F that day. Its data showed the temperature above 70 F from 10 to 4:pm, exceeding 80 F. from 10:00 am to 2:30pm; and a humidity drop to 20% at noon from an estimated mean humidity of near 95% for the previous 12 days(from Oct 1 to Oct 12 Renard 2001)

Some Monterey pine cones open within 5 minutes at air temperatures as low as 110 degrees F. (Dilworth unpublished data), significantly cooler than a fire and within the temperature range of a cone on a tree. This is in sharp contrast to Jack pine cones, which took 12 hours to open at 140 degrees. (Wessels)


HOPE intends to study the natural opening of cones in native Monterey pine forests. We will use microphones in mature trees to record the crackling sound of the cones opening and correlate their occurrences to temperature, humidity, time of day and date. The research will produce a map and a report.

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This Page Last Updated October 6, 2002