Trimming fir trees
We have roughly 8 acres of replanted fir trees now averaging 6" at the base. They are spaced 6-8' apart in roughly 8' rows. We would like to trim them up to allow some management of blackberries and weeds and to allow better grass growth as we use this area for horse turn-out. Would we be compromising the quality and value of our trees by taking off the bottom 25% of the limbs? And is fall and winter the appropriate time of year to do this?
Columbia County Oregon
Your plan is fine. As a general rule of thumb, you should prune no more than 1/3 of the live limbs at one time. And fall/winter is a great time to prune. Avoid springtime, when the bark is loose and you may inadvertently damage the tree.
Here's a short publication from Washington State Univ. Extension that has some diagrams on the proper way to prune to avoid tree injury.