Tree planting and site preparation in Western Washington

(Answers from Matt Provencher, WA DNR)

Q). How to deal with sod (e.g. if planting in old hay field)?
A). Afforestation is the hardest thing in forestry to do and getting things off to the right start is critical. Work must be done to loosen compacted soils, remove vole or rodent habitat and remove competing vegetation. Maintenance needs to be consistent to allow for tree root establishment, prevent animal browse or girdling and continue to reduce competing vegetation.

  • The compacted soil needs to be treated to a depth of at least 12” below the sod depth by tilling/disking.
  • Treating the grass with herbicide is best. If herbicide isn’t to be used, keep grass away from trees for at least 18-24 inches. A pre-emergent herbicide, such as Oust can prevent grass coming back after initial treatment. Diligence and elbow grease are the only options if herbicides won’t be used.
  •  If it’s a dry site, Douglas-fir and western white pine or ponderosa pine are good options. Even oaks if it’s really dry.
  •  Western redcedar can be used in wetter areas. Protect from deer. Also lodgepole (shore) pine, or Oregon Ash if it’s a wetter site.

Q). How can we support madrones?
A). Join the Arbutus ARME! You’ll find lots of good information on Madrone at that website, much more than I can give you in a short response to a question. If you have any questions about what you read, shoot me an email!

Q). How can flooding impact new trees during the dormant season?
A). So the short answer is brief flooding during the dormant season may not be an issue. Flooding can be an issue because it can alter soil conditions, interrupt gas exchange and cause some other issues. Many times, during the growing season, trees can tolerate this because they are not actively growing. The biggest question is going to be what are the conditions during the growing season? Trees can be more susceptible early in the growing season, after first flush so if the conditions are still wet – a high water table even if there isn’t surface flooding – trees could suffer. Of course, some trees are better than others at tolerating this, but perhaps just a few weeks of flooding during the growing season could potentially cause issues for many of our tree species.

Q). If I have 90% douglas fir and do selective thinning of smaller trees, does that mean I could replant western hemlock or western red cedar in the forest since those are most tolerant to shade?
A). In theory, yes. Even though cedar and hemlock are shade tolerant, they still need light for growth, so thinning can provide that light. There’s more to consider though. Are you soils able to support cedar and hemlock? If you have a droughty, rocky soil, perhaps not.

Q). Do you have any experience with Paulownia trees grown commercially?
A). I don’t have experience, though color me a skeptic. First, I don’t know that there’s enough Paulownia being planted to make it commercial. Mills are tooled to accept certain tree species. Different species may require different equipment – saws or especially dry kilns. The kilns are programed to dry certain species in a certain time, and this is different for most species. You’d have to have enough Paulownia to make this worth a mill’s while and I doubt a small forest landowner could affect mill operations in this manner. I also have concerns about its invasiveness. I’ve heard there’s a non-invasive variety, but I’ve seen at least one site where Paulownia took over. I think we have lots of native options for planting and growing commercially rather than Paulownia.