What to Plant after the Mountain Pine Beetle

by Jan Cashman – 2009

Most of you have heard about the Mountain Pine Beetle, the insect that is killing many of the pines in Southwest Montana.   If the pine trees in your yard are not infected yet, you may have a chance to save them by installing Verbenone repellent pouches in the trees and/or spraying them with the chemical Sevin in June.  But, if you, like many of us in the Gallatin Valley, have already lost pines to the mountain pine beetle, your quandary now is what to plant to replace those trees.

You are replacing a pine, an evergreen, which you probably planted in that spot because you wanted the qualities of most evergreens—green all year, tall and fast growing, providing screening both summer and winter.  Our best selling evergreen is Colorado spruce (Picea pungens).  Only in rare instances have spruce trees been susceptible to the pine beetle.  Although slower growing than most pines, Colorado spruce is a tree well-suited to our area.  Colorado spruce is denser than pines and its bluish short needles seldom winter burn.

Black Hills Spruce (Picea glauca densata) is another easy-to-grow spruce that is not quite as tall at maturity as the Colorado.   We like it for its deep green needles, its denseness and its perfect Christmas tree shape.  Similar in height to the Black Hills spruce is the native Engelmann spruce, another evergreen option.

My husband, Jerry’s first suggestion for a tree to replace dead pines was larch (Larix).   Native to western Montana, larch are tall and narrow conifers which lose their needles in the fall.  If you have visited Western Montana in October, you have seen the tall, pyramidal trees on north slopes turning a beautiful, golden color.  Then, the needles drop.  Although not native here in the Gallatin Valley, the larch we planted in our yard has grown quickly and well.  And, of course, winter burn is not an issue because its needles are not present in the winter to burn.

Firs are another evergreen that you could plant to replace pines.  Our surrounding mountains are full of tall Douglas fir (Pseudotsuga menziesii).  Or plant the beautiful Concolor fir (Abies concolor), which has long bluish-green needles.  (If you live in a windy, open area with heavy soil, Concolor fir may not be the best choice for you. It could winter burn.)

Nancy Berg, who works here at the nursery, suggests planting hardwood trees such as maple, oak, or linden as replacements.   She feels that the slower-growing, longer-lived hardwoods provide years of beauty and satisfaction compared to shorter-lived, soft-wooded aspens, cottonwoods, and chokecherries.

Many experts are suggesting replanting with the same pine variety you had to remove.  If this sounds risky to you, remember that serious pine beetle outbreaks occur only every 30-35 years or so, the beetles prefer mature trees to smaller ones, and it is hard to find a tree that is not plagued by some insect or disease.   So, if a Scotch or ponderosa pine was the tree you wanted for that spot, don’t be afraid to replant one there.  (To be one the safe side, I would wait a few years until this outbreak runs its course.)

There are many other trees that can be planted to replace lost pines.  Mountain pine beetle does not live in the soil, so you can replant a tree in the same spot without risk of re-infection.  Flowering and ornamental trees such as flowering crabs and Japanese tree lilacs are beautiful.  Or, plant something fruiting like an apple or cherry tree to feed your family.  But, for the sake of Bozeman’s urban forest, do replant.