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Serving small woodland owners and managers in the Willamette Valley and northwest Oregon
Updated: 14 hours 40 min ago

Knapweed

Fri, 08/21/2015 - 11:28am

By Amy Grotta, OSU Forestry & Natural Resources Extension – Columbia, Washington & Yamhill Counties

Like just about any small woodland, the Matteson Demonstration Forest has its share of invasive weeds. Besides familiar and ubiquitous foes such as Scotch broom and thistles, one of particular concern is knapweed.

Meadow knapweed, photo by Eric Coombs, OR Dept of Ag, bugwood.org

With purple flowers emerging from roundish bases at the top of a tall stalk, knapweeds superficially resemble a sort of spineless thistle, and in fact they are relatives of thistles, botanically speaking. They are biennial (2-year life cycle) to perennial plants and reproduce by seed. Fairly inconspicuous in the winter and spring; at this time of year, their purple flowers betray their location on and along roadbeds and other disturbed areas.

There are several species of knapweeds (Centaurea spp.) in Oregon, and all are classified as noxious weeds. Meadow knapweed, actually a hybrid of two other species, seems to be the most prevalent in the Willamette Valley.   Spotted knapweed is more of a problem on the eastside though has been documented on the westside too.

These two species can be tricky to tell apart, but we think we have meadow knapweed at Matteson, based on its wider distribution on the westside, the shape of the foliage and the color of the bracts (the tiny scale-like leaves at the base of the flowers).

So why are knapweeds a problem in forestlands? The biggest concern is their impact to native plant communities. They are tough competitors that can crowd out other desirable herbaceous plants, posing particular challenges to pasture or grassland managers, or those trying to restore meadows or oak savannahs. Even for those that do not have those particular objectives for their property, knapweeds are “road runners” in that they are easily spread by foot and vehicle traffic along roads and trails. So if you find that you have a knapweed infestation on your property, you can do surrounding property owners a favor by keeping it in check.

On the Matteson tract, knapweed is largely confined to gravel roads and open areas along the roads. Our main concern is limiting the spread of the weed, not only on this property but also to other College Forests and to other properties. For that reason, we are trying to keep OSU College Forest vehicles off the property as much as possible, so that tires and vehicle undersides do not pick up the seeds.  Multi-year herbicide treatments will also likely be necessary to reduce knapweed on the property; although because the weed is also prevalent along the county road ringing Hagg Lake, we may be fighting an uphill battle. We will be regularly surveying where our access roads join up with county roads and neighbors to contain and prevent its spread.

Roadbed infestation of knapweed with flowers and maturing seed heads, August 2015. Same road last October, showing mature seeds.

For more on knapweed management, consult these fact sheets: Invasive Weeds in Forestlands: Knapweeds from OSU Extension and Meadow Knapweed Best Management Practices from the King County Noxious Weed Program.

Thanks to Michelle Delepine from West Multnomah SWCD for her helpful expertise on this subject.

The post Knapweed appeared first on TreeTopics.

Categories: OSU Extension Blogs

Speaking of the weather…

Fri, 07/31/2015 - 3:00pm

By Amy Grotta, OSU Forestry & Natural Resources Extension – Columbia, Washington & Yamhill Counties

I don’t need to tell you it’s hot out there today. (Oops! I just did. Sorry.)

Between the extreme heat and the very real fire danger, it’s not a good afternoon to be working in the woods.  Rarely do I say I’d rather be in the office than in the field, but today is one of those days that I’m appreciating the air conditioning.

Since everyone is talking about the weather anyhow, it seems appropriate to share some reading material that relates to it, which you can enjoy in the comfort of whatever cool spot you’ve found today.  Oregon Forests and Climate Change is the subject of a little writing project which a number of my Extension colleagues have taken on as a group.

Why this project?  OSU Forestry & Natural Resources Extension strives to provide objective, science-based education to help forest owners succeed in forest stewardship. The growing body of climate science means that a basic understanding of climate and climate variability are needed to guide key aspects of stewardship of managed forests, such as:

  • selecting appropriate tree species and types of forest,
  • determining the timing of management actions such as planting and thinning,
  • estimating rates of growth and productivity, and
  • anticipating climatic stress and threats to forest health.

We realize there are still a lot of unknowns that go along with all this, so our intention is not to be prescriptive but rather to explore what some of the key issues might be. We’re learning as we go and sharing what we learn through a series of short articles.  The first set of these stories are available to read now over on the Oregon Forests & Climate Change blog. To set the stage, we get some perspectives on the subject of climate change from a woodland owner who also happens to be a forest geneticist working in the timber industry.

Crater Lake snowpack in July circa 1915. Photo credit: TheOldMotor.com

The next three articles address some of the basic principles of climate science. One looks at Oregon’s weather and climate as we’ve experienced it in our lifetimes vs. what is projected for the future. The next uses snowfall at Crater Lake as an example, in analyzing long term trends vs. year-to-year fluctuations in our weather. Finally, we look at some of the underlying factors that create these fluctuations, such as the El Niño cycle we are in right now.

These articles lay the foundation for the next phase of our project, in which we’ll be exploring how our forests respond to climate variability, extremes, and long-term change, and how we as managers can respond in turn. Stay tuned over the next year or so as we continue.

Of course, climate change can be a loaded subject and discussions about the topic can quickly grow rather heated. (I could not resist that pun…) We will be staying above the fray and look objectively at what anticipated changes may – or may not – mean on the ground, here in Oregon. So grab another icy drink and click here for more.

Thanks to the USDA Pacific Northwest Climate Hub and the Oregon Forest Resources Institute for providing financial support for this ongoing project.

The post Speaking of the weather… appeared first on TreeTopics.

Categories: OSU Extension Blogs