By Amy Grotta, OSU Forestry & Natural Resources Extension – Columbia, Washington & Yamhill Counties
It’s a familiar story. A few acres of Christmas trees were planted on the farm, perhaps for tax purposes, or because they were perceived as a low-maintenance investment, or maybe because the market was strong at the time. Fast forward a couple decades…the land has changed hands, and the Christmas trees, well, they never did make it into someone’s living room. Now, the new owner has “escaped” Christmas trees to contend with.
This is the situation at Tualatin River Farm, a 60-acre property now under a conservation easement and being turned into a working educational and demonstration farm and riparian restoration site. About five acres of the site is in this old noble fir plantation, presumed to have been planted for Christmas trees, and estimated to be about 25 years old. The new property managers wish to transform this area into a mixed upland forest, more representative of what might naturally occur on the site. What to do, they asked? Can these trees be saved?
- The stand displays all the visual signs of an overstocked forest: no vegetation growing on the ground, trees with a very high height-to-diameter ratio, and with a very low ratio of live canopy to total tree height. All of these add up to a situation where the trees are at an unhealthy density.
- The trees are so close together, that one can barely walk between them. Getting any of them down in a thinning scenario would be challenging. It might be feasible to remove every third or fourth row, but even then the stand would still resemble an orderly plantation…not the type of forest that is desired by the owner in this case.
The trees are noble firs, which make fine Christmas trees, but which would not naturally be found at this elevation (<200 feet) just above the floodplain. Here, they are an “offsite” species, and as they mature become more susceptible to diseases. Aerial photos show evidence of possible disease pockets.
So, can these trees be saved? Probably not. Given the owner’s goals, it’s likely best to start over with a clean slate.
A portion of this stand is in better shape. Presumably, some Christmas trees were actually harvested here, so that when the rest “escaped” the stocking was already patchier and less dense. And, the previous owner (who still lives on the site, as a caretaker) has been taking out trees here and there over the years for firewood. The remaining trees have a healthier live crown ratio (more of the tree’s trunk still has live branches attached); indicating that thinning probably started a while ago.
Choices for this part of the stand are not as clear-cut (pardon the pun). The managers wondered, should they continue gradually thinning out the overstory, and plant underneath with native trees and shrubs? Cut out a few patches to allow more sunlight in, giving the option to plant in more sun-loving species? As the nobles age, more will probably succumb to disease. They could become snags, which could be seen as an asset (for wildlife/structural complexity) or a liability (as a hazard tree – recall that the farm is to be used for education, with lots of kids and other groups visiting). There’s no right answer, but starting over might be the best option here too.
If this situation rings true for you, it’s important to remember that Christmas tree fields do not grow up to become healthy forests, at least not without some careful planning. Gilbert Shibley, a Clackamas County Master Woodland Manager, has developed some useful materials on the promises and pitfalls of converting escaped Christmas trees.
I had this problem 35 years ago, back when organic arsenicals could be used for top kill. One hack and squirt per tree killed the top 20 feet, but left the tree standing to support the others. Two treatments, 5 years apart, thinned it into a perfect stand as the residuals put on crown ratio and the dead trees rotted down. Is anything registered now for this type of use?
Similar to the hack-and-squirt method, girdling is another option to mechanically thin trees. Just remember, the top of the killed tree will eventually come down!