I purchased a home in Evanston this spring. It has a beautiful planting of white pines around the patio. The trees seem to be losing a lot of needles, and I am worried about the health of the trees. What can I do to help the trees?
— Beth Jones, Evanston
I visited a friend in Evanston last weekend whose home had several white pines. His white pines were also dropping lots of needles, leaving an attractive pine needle mulch on the beds under the trees. I really like white pines, but I hesitate to plant them in gardens with high clay content and high pH soil, as they struggle to grow. The sandy loam soil often found in Evanston gardens is great for growing white pines. You most likely have nothing to worry about.
Evergreen trees such as pines, spruce and firs lose the oldest or innermost leaves or needles naturally each autumn. The degree of needle loss can vary from tree to tree and year to year. Needle loss may be especially noticeable after a season of environmental stress, such as hot temperatures or drought. The normal pattern of seasonal needle loss begins with gradual, uniform discoloration and the eventual loss of inner needles from the top to the bottom of the tree. White pines tend to lose their needles more uniformly, so the loss is more noticeable. Usually, white pines have three years of needles in the summer and two in the winter. In some years, this species may only have one year of needles that remain attached for the winter. These trees may appear unhealthy when the yellowed needles outnumber the green ones of the current season. From your description, I would guess that you have a white pine that experienced heavy needle loss.
In general, there is no need to worry unless you see foliage turning from green to brown on the exterior part of the limbs while it’s still green on the interior or if the tree continues to thin out from year to year. Browning and loss of needles close to the center trunk is normal. Death of entire branches, needles with several shades of brown on the tree, or loss of needles just on lower limbs are also signs of problems. Improperly applied weed killers can damage trees in the garden. This damage would be visible shortly after application, so it is unlikely that weed killer application is responsible in this case. The weather was generally dry this past fall, and that may have contributed to a more significant needle drop.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.
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