Knowledgebase

White pine needles #603735

Asked October 22, 2019, 3:21 PM EDT

We have 2 large mature white pine trees on our property which usually shed hundreds of pine cones and sticky sap, and periodic needle drop. This year we've had very few pine cones and no sticky sap, but the needle shed is off the charts! Looking up into the trees, the yellow needles are still extensive, so there's more to come. Other neighbors in south Minneapolis are having the same experience. Why the difference in pine cone population and so many more yellow needles falling? So much rain?

Hennepin County Minnesota

Expert Response

The yellowing and needle loss on your 2 white pines is probably due to seasonal needle drop.  As much as one-half of the needles on white pines may drop in early fall. Seasonal needle drop is uniformly distributed throughout the inner part of the evergreen. The inner needles are the oldest needles. The older needles turn uniformly yellow or brown and drop to the ground. Note that the newer needles and growing tips should still be green and healthy.  White pine needles live for two years and then die and drop during the fall. Squirrels can knock off cones, stress, bad weather conditions during pollination, insects etc. Take a look at the attached link from more information https://dnr.wi.gov/wnrmag/html/stories/1996/dec96/cones.htm

 

Examine your pine trees for signs of insect and diseases. The following sites will help you diagnose why your pine trees have sticky sap. Golden sap comes from healthy trees. If you see any other colored fluid, your tree could have a pest or disease problem.

 

 http://apps.extension.umn.edu/garden/diagnose/plant/evergreen/pine/needlessticky.html

http://apps.extension.umn.edu/garden/diagnose/plant/evergreen/pine/needlesolderdiscolored.html

 

 

 
Pat M MN master gardener and TCA Replied October 22, 2019, 4:06 PM EDT
This is all good information, and I believe that our trees are healthy and having a seasonal needle drop.  But my question is why is this year so different from all previous years?  So many more needles dropping than usual, and so few pine cones.  Are there cycles that the tree goes through in the pine cone process, or is it a function of the weather?
The Question Asker Replied October 23, 2019, 9:57 AM EDT
Each evergreen species has its own timetable for flower development, pollination and cone maturation. White pine cones take two years to mature. Pine tree produce a lot of cones on some years and few in other years. White pines retain needles for three years, but in autumn, 2-or-3-year-old needles change color and drop, leaving only the current season’s growth still attached. Some years older needles fall off slowly. Other years, large numbers of needles drop simultaneously. Needle drop is triggered by the weather and the season so many evergreens show symptoms at the same time.






Pat M MN master gardener and TCA Replied October 23, 2019, 11:18 AM EDT

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