Did your white pine tree lose a lot of needles this fall? Don’t worry, it’s probably fine.
“It’s normal for evergreens to drop their oldest needles every autumn,” said Sharon Yiesla, plant knowledge specialist in the Plant Clinic at The Morton Arboretum in Lisle. It’s part of their way of life.
“A white pine will discard needles that are three years old,” she said. “If your tree dropped a lot of needles this fall, it just means the tree had a very good year and grew a lot of needles three years ago. The tree isn’t dying.”
Needles, which are long, slender leaves, stay green throughout the year on evergreen trees and shrubs. But they don’t last forever, any more than maple or lilac leaves do. “Needles only live for two to four years, depending on the plant species,” Yiesla said.
Every spring, new green needles grow at the tips of branches. Every fall, the oldest needles, closest to the trunk, turn yellow or gold and drop off. That’s why the ground in a stand of pine or spruce trees is softly carpeted in old needles.
Evergreens may seem to be unchanging because they have green needles all year. It can be alarming to notice some of those needles dropping, although it happens every year.
Seasonal needle drop is especially conspicuous on pine trees because they have an open branch structure and they bear (and lose) their needles in bundles of two to five.
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“Arborvitaes, spruces and firs lose their older needles every year just like pines do,” Yiesla said. “It’s just harder to see into the interior of an arborvitae than a pine.”
The oldest part of any branch is closest to the trunk, and that’s where old needles are discarded. “Not much sunlight reaches the interior of an evergreen tree,” Yiesla said. “Without light, needles can’t survive there.”
The life span of an evergreen needle depends on the species, from two years for white pine (Pinus strobus) to four years for red pine (Pinus resinosa). “As long as your tree is only losing older needles, it’s normal and it’s nothing to worry about,” she said.
Needle browning is only a possible sign of trouble if it’s happening somewhere else. If you see brown, dead needles only at the tips of pine branches, where new needles are normally added in spring, it may be a sign of diplodia tip blight.
A single brown branch or a large brown patch on any evergreen can indicate winter damage or an insect infestation. When an entire pine tree turns brown, or if it turns brown in patches or from the bottom up, it may be a sign of disease, such as pine wilt.
Needles turning brown and dropping from all over a tree or shrub often means the plant is stressed by drought. “Evergreens need water all the time, even in fall,” she said.
Because brown or dropping needles from newer parts of branches can be symptoms of so many different issues, always seek expert help to get a firm diagnosis before you attempt any treatment. The Arboretum’s Plant Clinic (mortonarb.org/plant-clinic) can help find the source of the problem.
Needles that only fall in autumn, from the oldest parts of the branches, are no cause for concern at all. “It’s part of the tree’s cycle of growth and renewal,” Yiesla said.
For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.