Improving Air Quality in Eugene
How trees can help address winter inversions
Residents of Eugene and Springfield are very familiar with inversions. On a cold, clear winter day, pollutants get trapped in the valley, hanging low like a fog and causing notably poor air quality for people on the ground.
“On a cold, dry day, you can pretty much expect an inversion,” says Friends of Trees Eugene Director Erik Burke. “It’s not uncommon to see air quality alerts in winter.”
In the Eugene metro area, the main culprits are car emissions and wood smoke. Particulates in the air get trapped in the valley by warmer air above. It can lead to uncomfortable and even dangerous levels of air pollution. Because Eugene is at the southern end of the Willamette Valley and further away from winds coming from the Columbia River, it’s more susceptible to inversions than the Portland metro region.
One thing that can help? You guessed it, more trees! Trees improve air quality by providing surface area for airborne particulates to stick to. Those particulates are then washed by rain into the soil, where microorganisms break them down into something less harmful.
By breaking down pollutants, soil functions like a kidney of sorts. Trees help guide and slow water through the soil, making trees huge contributors to both air and water quality in both natural and urban environments. As Erik puts it, “trees are stormwater facilities.”
Like in plenty of other cities, the neighborhoods that are closest to polluters in Eugene are low income neighborhoods. Air quality is one of the many benefits of trees that low-canopy neighborhoods are deprived of. Friends of Trees plantings in the Bethel neighborhood are in part to address air quality concerns there.
“All trees are good at improving air quality,” Erik says. “We’re trying to get trees in the ground where air quality is worst.”
This is one of the reasons Friends of Trees plants along the railyard and the Northwest Expressway, where idling locomotives and automobiles are releasing particulates.
While all trees improve air quality, evergreens are particularly useful because they keep their leaves or needles all year.
“Most of our rain comes in winter,” Erik says, “so evergreens are essential. We have a lot to learn about evergreens and air quality.”
Most of the evergreens in Eugene’s urban forest are conifers rather than broadleaf evergreens. While we often think of conifers when we think of evergreens, other species like California live oaks, holm oak and California bay laurel also keep their leaves year-round. Many evergreens grow to be quite large, so the Eugene team is looking to incorporate smaller evergreens like toyon into their plantings.
Eugene Bicycle Plantings
Biking Our Way Into the New Year
Why take a car when you can take a bicycle? The Eugene Branch has always taken that mindset and incorporates bicycle crews into every neighborhood planting event.
“We have some really dedicated bike volunteers,” says Eugene-Springfield Program Manager Taylor Glass. “That’s how we can always have a bike planting crew.”
Bike crews are able to transport trees and tools from the staging site to planting locations by using bicycle trailers. In addition to our own trailers, Hummingbird Wholesale often joins us for a planting with their large electric-assisted bike trailers so that we can transport even bigger loads.
Using bikes instead of cars is a reflection of our desire to take care of our environment, and it makes perfect sense to reduce emissions at a bike planting. Beyond that, it’s just plain fun.
“I just love it,” says Eugene Director Erik Burke. “It’s so fun to see the look of amazement on people’s faces when a whole crew rides past hauling big trees. And when treecipients see us pull up, they’re so surprised to see we biked their tree over.”
To give even more community members a chance to participate as a volunteer on two wheels, The Eugene Branch partners with a local bikeshare, PeaceHealth Rides, to have their bikes available at events and free to volunteers. In the past, we’ve had about one event per year with PeaceHealth Rides, but this year we’ll have three! The first will be on January 7th.
With success, fun, and enthusiasm from volunteers, Friends of Trees hopes to have more and more bike crews at plantings in every community we work in.
Eugene’s Winter Trees
Our Favorite Trees to Watch in Winter
Many trees have shed their leaves and are on their way to being dormant for the winter. But not all of them! Late fall and winter in Oregon and Washington is still a wonderful time to admire trees. Our Eugene team put together some of their favorites to watch out for this time of year.
One of the most brilliant fall trees is the gingko, whose intense yellow leaves tend to fall all at once, thanks to their unique stems. Although ginkgos have “broad” leaves, they are actually more closely related to conifers. The modern ginkgo has changed little since its ancestors first graced the planet more than 200 million years ago—tens of millions of years before the advent of conifers and more than a hundred million years before broad-leafed trees became abundant.
For many the Douglas-fir, Oregon’s state tree, is a quintessential evergreen conifer, especially as many of them head into our living rooms for the holidays. Douglas-fir dominates local woodlands, and is joined sometimes by valley ponderosa pine, incense-cedar, and grand fir.
Conifers like the Doug-fir are perfectly adapted to our area’s wet winters and dry summers. Part of what makes Eugene special is that while the urban forest is composed largely of broad-leafed deciduous trees, it’s punctuated with firs, incense-cedars, giant sequoias and other conifers.
One of the many reasons we love evergreen conifers—they work year-round, producing oxygen and storing up carbon through photosynthesis, and providing important stormwater benefits by intercepting precipitation in their dense canopies.
Another favorite? The Atlas cedar, one of our true cedars. You can tell the cones of true cedars, like the atlas cedar, because they stick up vertically and shed their bracts one by one while staying attached to the tree.
The Atlas cedar notable is this time of year because it’s already releasing its pollen. Many conifers, in particular, “bloom” during late fall and winter. Atlas cedars (Cedrus atlantica) have exceptionally large and showy pollen cones, sometimes two to three inches in length and up to half an inch in diameter. The spent pollen cones are most noticeable after they have fallen, when they carpet the ground beneath the tree with what look like big, fuzzy, yellow caterpillars.
Keep in mind, wind pollinated trees are responsible for allergies, rather than showy flowers. Trees like the incense cedar will be putting out pollen in December. But the rain might save us—heavy rain will knock the particulates out of the air, cleaning them up for us.
Many people have the impression that, during the winter, trees—especially broad-leafed deciduous ones—are completely dormant. But thanks to relatively mild winters in western Oregon, it’s possible to find at least one species of broad-leafed tree—and sometimes several or more—in bloom during any given month of winter. In December, the long, dangling, pollen-bearing catkins of European filberts begin to develop—and the tiny, magenta female flowers do, too, though they’re not nearly as conspicuous. And in January, we begin to see the first elm flowers. Keep your eye out for these lovely signs of life!
Eugene’s Northwest Expressway Plantings
Two Decades of Planting along the Northwest Expressway
Every season, the Eugene Branch kicks off its planting season along the Northwest Expressway, a five-mile stretch of road parallel to the railroad. It’s not the most glamorous of planting sites, but there is plenty of available space for large trees to grow and provide their benefits to the community.
Friends of Trees volunteers will gather in Eugene on November 5th for Phase 9 of this planting project. The land is owned by Lane County and abuts the Union Pacific railyard. Friends of Trees picked this annual planting project up in 2013, but it actually started back around 2000, with what we now call Phase Zero, planted by the Eugene Tree Foundation (which became Friends of Trees – Eugene). That first planting has grown into sizable shade trees, and has served as the site of a condoned homeless camp for veterans in Eugene.
“Those trees are now providing shade to people,” says Eugene Director Erik Burke. “It goes to show that trees can still have benefits when they’re planted in places besides private property.”
For these Northwest Expressway plantings, the Eugene team is creating pods of plants. After removing a eight-foot diameter of grass, they’ll plant one-to-four trees and four-to-six shrubs. In addition, this year they’ve added camas bulbs to the recipe, and will also be adding native milkweed and Douglas’ aster.
Installing understory layers in addition to trees is an approach that the Eugene team hopes to expand on for all their plantings. This year, they’re offering camas bulbs as an add-on for neighborhood tree recipients.
“We really want to be creating habitat for native pollinators,” Erik says. “So we’ve got 900 camas bulbs to plant this season.”
This year at Northwest Expressway, they’ll plant 20 trees, 50 shrubs and 50 herbaceous plants along Northwest Expressway.
“We started planting at the southern end of the expressway, then moved to the north, and now we’re filling in the middle,” says Eugene-Springfield Program Manager Taylor Glass. “We’re required to space these pods out a bit, but that means we have plenty of space to plant trees that will grow to be quite big.”
The next time you’re driving on Northwest Expressway, keep your eye out for incense cedars, Pacific madrones, valley ponderosas, giant sequoias, and California laurels. What used to be an empty stretch of grass is on its way toward being a happy home for trees.
Community Pruning in Eugene
Community Pruning—An Art and a Science
The Eugene Branch is in the heart of its pruning season, and has already hosted several successful community pruning events. They’ve been keeping these pruning events small and intimate so that each volunteer gets more hands-on experience. Pruning can feel like an art as much as a science, and it’s something that takes a lot of practice before you feel comfortable with it.
“We’ve had smaller pruning events in recent years because of Covid,” says Taylor Glass, Eugene-Springfield Program Manager for Friends of Trees in Eugene. “We decided to keep it small because the pruners really appreciate it.”
Each pruning event has just 15 volunteers, and they split into five groups, with one Friends of Trees staff member on each team. They prune to provide clearance over the sidewalk and the road, and they prune for good structure. In many but not all species, this includes encouraging a strong central leader.
One reason that Eugene prunes in late summer, rather than in the dormant season, is that it slows the trees down. “Here, fast growth is a bigger issue than slow growth,” Erik says. Fast growing trees are tougher to manage for strength and stability, and will often have weaker wood more prone to failure, particularly in snow or ice storms, which is something you don’t want in the urban environment.
“Young tree pruning is the most cost effective thing you can do for an urban forest,” says Eugene Director Erik Burke. Pruning helps create a lasting form that won’t suffer as much damage from storms and trucks.
When you walk up to a tree that needs to be pruned, it can be tough to know where to start. Every tree is different. You have a number of goals you want to achieve, but you can only prune so much. Each pruner might make different little decisions toward the same overall goal of forming the tree.
“It’s so personal, the approach each person takes,” Erik says. “We all do it totally differently and no one way is right.”
The small pruning teams allow for a collaborative decision-making process, which grows a volunteer’s experience and confidence. And with experience and confidence, a small team can accomplish just as much as a big group.
“Volunteers can be anxious, because they want to do it right,” says Erik. “But the trees are resilient, and they’ll be fine in the long run.”
Ideally a tree gets pruned every three years for the first fifteen years of its life. We’re not always able to provide every tree with the ideal number of prunings, but thanks to volunteer efforts, we can often give trees pruning attention that they need.
Pruning a tree can be really satisfying, when you step back and look at its form take shape. And it can be especially rewarding when you see the tree grow into that form over the years. Giving volunteers hands- on involvement in the process creates a special bond to these community trees, and volunteers always want to come back to do it again.
“Teaching is a great way to learn,” Taylor says. “And with each season, you learn more.”