Q: I’m wondering why there seem to be thousands of pine cones on the ground this year. I hope you can write an article and reference what might be causing this and if it may have any correlation to climate change.
A: It would be helpful to have a bit more information, such as if you are wondering about green pine cones on the ground or brown/gray mature pine cones. We’ll answer this question as if the pine cones are mature brown ones.
Pine cones and pine trees belong to a group of plants called and have existed since prehistoric times. Pine cones are how the trees reproduce. Each pine tree produces male cones and female cones. The male cones produce pollen, are typically very small and grow mostly on the lower branches. The female cones are larger and have woody spirals, which are designed to keep the seeds of the tree safe. Male pine cones have a short life cycle, while the larger female cones have a longer one.
Male cones produce pollen, which drifts into the air and fertilizes the female cones. Once fertilized, the woody spiral cases of the female cone can open and close to protect the seeds from being eaten by animals, from low temperatures, and from the wind. Pine cones stay on a tree until the seeds are mature, which can be anywhere from 2 to 10 years. Typically, pine cones open and release their seeds and fall to the ground in warm weather, when there is a better chance for the seeds to germinate. Jack pines, one type of pine tree, only release their seeds when they are exposed to a hot fire.
Pine trees don't produce the same number of cones every year. In wet years, trees put more energy into growing than into reproduction, so they have fewer cones. In drier years, the trees focus more on reproduction and produce more cones. Pine trees also vary the cone and seed production to throw off the insects that eat the seeds. If the pine cone production cycles are more erratic, the insects can't adjust to the cycle and prey on the seeds and cones.
Pine trees can be expected to have a bumper crop of pine cones every three to seven years.
It is possible that changes in climate could have an effect on pine cone production and seed release, since they are influenced by temperature and moisture. In Minnesota, we are seeing higher temperatures, milder winters and changes in rainfall patterns. There’s more information about climate’s effect on red pines here:
And more fun facts about pine cones in general here:
Written by U of M Extension Master Gardeners in St. Louis County. Send questions to firstname.lastname@example.org.