Many White Pine trees turn yellow at this time of year. Is your white pine tree dying? Probably not, but let’s take a close look at your tree and see if there’s anything to worry about, or anything you need to do.
Most likely you’re seeing normal “needle drop” on the inside branches. Is this year’s new growth at the tips of all the branches still green and lush? Probably. The needles further back on each branch are yellowing and falling off, piling up under the tree. We call this pileup of needles “self-mulching” because it helps prevent weeds while actually feeding the tree.
Eastern white pine trees don’t have needles on their inner branches. Each year, last year’s needles die and fall off, not to be replaced. The current year’s growth remains green. For this reason, the only green needles on the tree are all around the outside, and the inner branches are bare from that point on.
White Pines are among my favorite trees. They grow rapidly into stately, gently swaying, plush cone-shaped giants. The wind blowing through them makes a unique, restful rushing sound. The soft bed of needles underneath is very acidic, and the combination of acid needle mulch and deep shade under pines is ideal for some of my favorite shade-loving plants.
White Pines aren’t ideal for privacy screen or windbreak, because the soft wood breaks easily under wind or ice loads, leaving the lower portion of the trunk bare on mature white pines. Still, a grove of white pines or even a solitary mature example are very beautiful in the landscape. It’s worthwhile to keep a sharp eye out for some common white pine problems, and fix them as soon as they appear.
BAGWORMS like to nibble on white pines. Symptoms include needle drop, partially chewed needles that turn brown where they’ve been chewed, and the presence of cone-shaped hanging bags made of chewed needles and bits of twigs. These are the bagworm’s portable homes, and are sometimes mistaken for small pine cones. They should be sprayed, or treated with a 12-month drench.
WOODPECKERS sometimes create little holes arranged in neat rows, on the smooth bark of white pines. They are a sign of Yellow-bellied sapsuckers; woodpeckers that create rows of holes on the trunks of certain trees and often return to the same trees year after year, along with their offspring. Heavy feeding can damage young trees. We discourage them by spraying black tree wound paint into the holes.
WHITE PINE DECLINE causes pale green or off-color limp, drooping needles that later turn brown. The bark may be spongy and may shrivel and ooze sap. Usually the entire tree is affected at once. Trees usually do not recover and death occurs within four weeks. Causes might be a combination of drought, compaction under the tree or disturbance of the root zone. I’ve seen many cases where there is paving close by, causing the tree roots to run out of room as it grows, and leading to drought stress. To prevent white pine decline, avoid machine traffic or digging under the tree, and give your tree a weekly deep-root soaking during drought.
Steve Boehme is a landscape designer/installer specializing in outdoor living spaces. “Let’s Grow” is published weekly; column archives are online at www.goodseedfarm.com. For more information call GoodSeed Farm Landscapes at (937) 587-7021.