White Pines Aren’t Dying

I have received several calls recently from homeowners concerned that their white pine needles are turning yellow and dying. For most of these homeowners, I’ve been able to allay these fears because annual needle drop is normal.

All needle-evergreens lose their oldest needles each year. In the case of white pine, the oldest needles turn yellow and later fall. The striking yellow color elicits fear in homeowners, who speculate that their trees will soon succumb due to some mysterious disease going around.

Most of our white pines are just fine. If the yellow needles are on the inner part of the branch and needles near the tip are still green, your trees are probably in good shape.

Evergreens like pine, spruce, fir, arborvitae, and hemlock only retain the newest year’s needles (2 or more years), and naturally lose their inner (oldest) needles on established trees each year.

Gail Ruhl, Sr. Plant Disease Diagnostician and Rosie Lerner, Consumer Horticulture Extension Specialist, both retired from Purdue University, recently wrote about normal fall needle drop.

“Evergreen needles have varying life spans, depending on the species,” they said. “White pine needles live for 2 years while other pines have needles that persist 2-6 years, depending on species.” They said that spruce needles live 3-10 years.

“Some species of evergreens have a more noticeable leaf drop than others, shedding many needles all at once, while others shed a little at a time such that it is hardly noticed,” they said. “White pine and arborvitae have very dramatic annual shed which can be quite alarming if you don't realize that it's perfectly normal.” Needles on the older branchlets of arborvitae turn brown and remain on the tree for a while before shedding.

Although white pine lose their needles in autumn, the experts said that needle drop in other evergreens is not always in the fall season. For instance, the older needles of yew shrubs will turn yellow and drop in late spring or early summer.

So, when should you worry?

In some cases, you may see all the needles on a branch turn color. Moisture extremes may have stressed some trees to the point that they may lose branches or die because of accumulated stress.​ Other stress factors could be in play, such as poor site conditions, insect pests, or diseases.

Will the branch survive?

First, check to see if the branch with the browning needles is alive.  Scrape off a small area of the "bark" of the branch with a sharp knife. “There should be green tissue immediately under the bark,” they said. “This green cambium layer is quite thin with the underlying woody tissue being white.” If there is no green at all, the branch is dead. 

Also check the ends of branches. “Dry, brittle twigs indicate that at least that part of the tree is dead,” they said. “Dead branches should be removed.” Major branch removal may destroy the aesthetics of the tree, making tree removal the only viable option. Dead trees should be removed promptly to avoid attracting borers.

What can you do?

The experts recommended concentrating on good watering practices during dry periods. “A general ‘rule of thumb’ is to supplement natural rainfall to apply a total of one inch of water per application, about every 7-10 days until the ground freezes,” they said.