GUEST OPINION: Why your evergreens might not stay green

By ALYSSA BESSER, guest columnist

This time of year I hear concerns about pine health, from individual branches dying to dramatic needle drops. People share concern over their evergreens staying, well, green.

There are a number of ailments for the white pine. While pine trees are able to adapt to a wide variety of soil types, the heavy clay soils of Brown County can aid in a shortened life for this tree.

“White pines grow best in slightly acidic, well-drained soils high in organic matter. The alkaline, heavy clay soils found throughout much of Indiana are not favorable for optimum white pine growth,” says Rosie Lerner, Purdue Extension consumer horticulture specialist.

“Drought, excessive moisture and soil compaction are additional stress factors that can contribute to decline. Declining pines attract insect borers, which will damage the inner bark tissues, accelerating the tree’s demise.”

Evergreen needles have varying life- spans, depending on the species. Pine needles live for two years. In autumn, white pines can have a dramatic needle drop, which can be alarming if you do not know about this natural process.

“Pines survive for anywhere from 10 to 30 years before starting to decline and die,” says Purdue Extension Educator of Vanderburgh County, Larry Kaplan. “This is especially noticeable on disturbed sites (subdivisions etc.) and areas where the trees are not irrigated during the summer. I have noticed that they will limp along until they get one stress too many — drought, soggy spring, etc. Then, annual growth begins to decline rapidly over two to three years, and the tree is dead.”

How can you tell if your yellowing needles are part of the natural die-back cycle?

“If, at this time of year, the needles are turning yellow on the inside of the tree, and the needles farthest out on the branches remain green, the tree is most likely exhibiting natural needle drop,“ says Lerner.

While pruning excess growth and dead limbs can help open the plant to more light, it should be noted that pine growth comes from the tip of the branch, and trimming too far back can disfigure the tree.

How can you tell if the branch will 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. 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,” says Lerner.

“Also check the ends of branches. Dry, brittle twigs indicate that at least that part of the tree is dead. Dead branches should be removed and dead trees should be removed promptly to avoid attracting borers.”

There are measures you can take to reduce stress on your evergreens, such as watering them until it freezes, removing dead material, etc. But keep in mind that these trees can be easily stressed, and they are possible already growing in a space and soil not suited to their thriving.

Alyssa Besser is the Brown County Purdue Extension educator for agriculture and natural resources and 4-H youth development. She can be reached at 812-988-5495 or abesser@purdue.edu.