By Jeff Rugg- Q: On the news, I have seen amazing pictures of the clouds of pine tree pollen in North Carolina. Why is there so much this spring? Is there something wrong with the trees? Why are the trees producing so much pollen?
A: There is nothing wrong with the trees. There are many cycles of growth in nature, and sometimes they overlap. Seven years ago, I was in North Carolina in mid-February, and the cars were covered in pollen. From what I have read, this year’s pollen clouds are only as bad as the ones six years ago, so it is a common occurrence that we just don’t remember or hear about very often.
Each year, plant growth shifts depending on the weather. Some trees release their pollen early and some later, but if the weather is cool for a while and then rapidly warms up, both sets of trees may release their pollen around the same time. What would have been spread out over time is now concentrated over a shorter time.
In order for a tree to produce a lot of pollen very early in the spring, it must have stored a lot of carbohydrates during the summer before.
There hasn’t been enough warm weather for the trees to produce those carbohydrates this spring. With so much pollen in the air, the trees will probably produce a large number of pine cones this year. Some pine species take a couple of years to grow the cones to maturity. Producing cones requires a lot of carbohydrates, so the trees will not produce as much pollen for the next couple of years.
Apparently, the pine trees in this area of the country require about six or seven years to cycle through the production of lots of cones. There will be an increase in the population of birds, mammals and insects that feed on pine seeds during this time.
This type of boom-and-bust cycle is common in nature. When oak trees in an area go into a boom cycle, the population of deer and squirrels increases. When the spruce trees in Canada go into a bust cycle, many bird species move south to the States to find food over the winter.
Many landscape and food crop plants are wind-pollinated, including all grasses, ash, cedar, corn, birches, broccoli, hickories, juniper, oaks, peas, pines, poplars, ragweed, rice, spruces and willow. You will notice there are several plants on the list that cause allergies. None of these listed plants have showy flowers, but they do have other landscape benefits.
You might think that it is waste of energy for a tree to produce so much pollen. That may be true, but the tree doesn’t have to produce flower petals, nectar or a fragrance, so there is a savings there.
It is not just wind-pollinated trees that go through boom-and-bust cycles. It is common in fruit trees such as apple, crab apple, peach and pear. Fruit tree growers purposely thin out some of the developing fruit each year to prevent the tree from producing too much fruit in one year. Otherwise, the tree would produce too few the next year. A moderate amount each year is a better way to run the orchard.
Email questions to Jeff Rugg at firstname.lastname@example.org.