Dripping Cones

7 September 2012

As I’ve said before I live in a deciduous place so the ways of conifers are sometimes mysterious.

Take pine sap for instance.   My annual visits to Maine have taught me to check before sitting down under a white pine.  Mainers know that their state flower drips sap (yes, white pine cones are the State Flower of Maine) so they don’t put lawn furniture in the drip zone.  I had some unfortunate experiences with pine sap before I learned this.

Only the female cones cause this problem.  Male cones are small pollen-laden structures that appear in the spring at the base of new growth.  They release huge amounts of pollen, then fall off the tree.

The female cones form on the branch tips and capture the wind borne pollen. It takes two years for them to mature into the familiar woody cone that opens when dry to release the seeds.  Along the way they’re green and drippy.

Why do immature cones drip sap?

That question spawned this post but I haven’t been able to find the answer.

However I have some theories.

  • Theory 1:  The cone has to dry out as it matures. Maybe dripping is part of that process.
  • Theory 2:  Pine sap has insecticidal properties.  Maybe the oozing sap keeps insects away from the developing seeds.
  • Theory 3:  Maybe the sap also keeps squirrels away from the immature cones.

I don’t know why they drip, but the sap certainly keeps me away from them.

p.s.  If you know why pine cones drip sap, please leave a comment and let me know. It’s driving me nuts!

(photo by Steven J. Baskauf from Vanderbilt University Bioimages)

10 thoughts on “Dripping Cones

    1. No, because the resin starts dripping long after pollination takes place. In addition pollen germination requires aqueous solution not terpenoid resin.

  1. I believe you had it correct with both #2 and #3, Kate….it is a repellant to both animal and insect while the seeds develop…
    since it takes over a year for the cones (and seeds inside) to fully mature, it has to keep the pests away from the slow developing seeds until they have matured…
    The seed that fall out of the ripened cone look like little maple “helicopters”…Most have released their seeds in Ohio already and there is a bumper crop of them (and the dried dead cones) from the perfect spring weather conditions back in 2010….

  2. My white pine is dripping a lot. I’ve had the tree for over 20 years and have never seen this. However, the squirrels are eating the immature cones like crazy.

    1. We’re experiencing the same dripping white pine cones & have never before in 25 yrs. They’ve been dripping all over our patio & its an annoyance to step in it barefoot & have to scrub our feet with nsil polish remover. I’m wondering if we could trim the immature cones off the trees or would that hurt the tree?

  3. Mine are dripping all over the driveway and walkway. I’m having a cement driveway installed in a couple of weeks is it going to damage the new concrete?

  4. I live in the Upper Peninsula of Michigan and I am also having a lot of trouble with my White Pine. Sap is dripping over everything, and green, sap covered pine cones fall all over every day as well. I don’t remember having this problem in the past. At first I thought the squirrels were knocking them off the tree, but now I wonder if they are falling because our summer has been so dry. I swept them all up last night and this morning I hear them dropping all over my deck and patio again! Any thought?

    1. There are a couple of possibilities:
      1. It may be that your pines are having a high mast (seed) year in which they produce more cones than usual. More cones = more sap. Many species vary their mast years as described in the Charlotte News: “[Some trees] produce mast at irregular intervals, withholding production for several years and then producing a massive abundance of seed. This method allows trees to “starve” the predators of their seed for several years, lowering their populations, and then overwhelm them with more mast than they can eat. The intervals at which these “mast years” occur varies by species, from red oaks (every two to three years) to sugar maple (every two to five years) to red spruce (every three to eight years).”

      2. It may be that the weather, climate or insects have stressed the trees and they are producing an overabundance of seeds (cones) as a species survival strategy. Our white ash trees did this a decade ago as they were dying of emerald ash borer.

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