Tree Care

Leaflet: Spring Tree Care

Spring has Sprung – What that means for your trees

Spring has truly come in fits and starts this year. Some of us might still feel like it’s winter, and some are ready to announce that Spring has sprung! Trees are the same way when it comes to breaking dormancy. Some are early risers, and some sleep in. A bunch of factors go into it, including species, daylight, and temperature.

Spring is the perfect time to notice seasonal cycles. The study of these periodic events in biological life cycles is called phenology. When does a tree go dormant, when do you start to see buds, how long is the growing season? We can see quite a range among species.

“Cornelian cherries normally bloom about this time of year,” says Neighborhood Trees Senior Specialist Andrew Land. “Whereas a few years back, someone approached me about an Oregon white oak that they thought was dead, until it finally broke bud in June.”

Andrew and other staff at Friends of Trees keep an eye on phenology as it particularly relates to survival. They take note of trends in trees’ responses to different stimuli like light and temperature, with the intent to prioritize the most climate adapted species.

Here are some things you can do to take care of your trees this time of year.

Mulch Madness

It’s a great time to refresh mulch as needed. The objective is to mulch the tips of the roots as they grow outward from the base of the trunk. They will grow into soil that’s moderate in temperature and contains moisture, factors that mulch will provide. Because the roots are growing outward, when you mulch trees in their second year in the ground, aim for more of a 4-5′ diameter ring of mulch, still 3” thick, about a foot from the base of the trunk.

You may have noticed that some trees hold their leaves through winter. They’re called marcescent leaves, and they are a sign of last season’s growth. You’ll see them on native oaks like Oregon white oak (Quercus garryana) and scarlet oaks (Quercus coccinea). Come spring time’s flush, these leaves will be shed to make room for new growth. You can use these leaves as mulch!

Go easy on the pruning

It’s best to go easy with regard to pruning during “bud break.” This is when sap is rising up the tree, after having dropped to the roots in the fall. As the sap is rising, some trees (maples, for example) will “bleed” if pruned as sap is rising. It’s not harmful to the tree—that’s where maple syrup comes from, after all—but it can be disconcerting to see.

Weekly Watering

It’s almost time to start weekly watering for newly planted trees. “Deep and infrequent” is the recipe for success. Starting mid-April, 15 gallons all at once, once a week is ideal. Either a gator bag, hose on a gentle trickle for maybe 20 minutes, or a 5-gallon bucket with three 1/8″ holes drilled on the side at the bottom and filled 2-3 times consecutively works great.

If the temperature gets over 90 degrees, bump that up to twice a week. If we see another heat “event” coming, a good, deep soak beforehand is very wise as preventative medicine.

More tree care here!

Tree Care

Leaflet: Native & Climate-Adapted Trees

Considering Natives and Climate Adapted Non-natives

The right tree, right place ethos is complicated by urban environments and climate change

We invite you to consider the cascara (Frangula purshiana), a tree native to the Pacific Northwest. It has pretty autumn colors, does well in both shade and sun, and is a great backyard habitat tree, with small berries that attract native and migrating birds. This low-maintenance tree is a wonderful native option for your street or yard, and we still have plenty available in our tree store this season!

We’re big fans of native trees at Friends of Trees. It’s important to steward native plants as food and shelter for native animals, and in so many instances, natives are the right choice when you’re looking to put the right tree in the right place.

“There’s always a place for native trees in our hearts and in our gardens,” says Neighborhood Trees Senior Specialist Andrew Land. “But there’s also a place for non-native, locally hardy trees in the urban environment.”

The urban environment presents unique challenges to trees that would otherwise do well in a forest. Concrete and asphalt trap both heat and cold. The soil is often stripped of top soil and compacted. And trees are usually stranding alone, rather than part of a multilayered forest ecosystem.

Urban spaces are also usually a degree or two warmer than natural areas, which is only made worse by climate change. Some local species, like the western red cedar, are already struggling due to warmer temperatures.

“The climate is changing, and we can anticipate it continuing to change dramatically,” Andrew says. “So it makes sense to consider trees that would do well here, especially if they’re drought-tolerant free of pests and disease. We’re told to consider planting trees that thrive 500 miles south of here, because those should thrive here in 20 years based on climate change models.”

One such non-native is the ‘Persian spire’ Persian ironwood (Parrotia persica ‘JL Columnar’), a columnar cultivar of a tree native to Iran. It’s drought-tolerant, has no problems with pests or diseases, and is expected to do well as a street or yard tree in the face of climate change. It’s a great alternative to cascara that you should have no qualms about selecting.

Another is the swamp white oak (Quercus bicolor, shout out to our Year of the Oak!), which is native to eastern North America and one of our favorite oaks. It turns out that trees well-suited to swamps also do really well in urban environments. Their roots are accustomed to anaerobic conditions. Whether they’re underwater or under concrete, they can handle a lack of oxygen. 400 swamp white oaks were planted at the 9/11 Memorial in New York City.

The American hophornbeam is another great backyard tree. It’s native to eastern North America, and has flowers that look like hops, a characteristic that makes them feel right at home here.

“When it comes to considering trees for our urban forest, variety is really the spice of life,” Andrew says. “If a disease or pest takes out a particular species, you don’t want that to be the only tree you have. Diversity creates resilience.”

Tree Care

Emerald Ash Borer

What we can do in response

The discovery of the emerald ash borer in Oregon has many people rightfully worried about the fate of ash trees in our region. The Emerald Ash Borer, or EAB, is an invasive wood boring beetle that feeds on ash trees. There are thousands of wood boring beetles in the world, and most cause no problems at all, but EAB isn’t native to North America, where it has fewer natural predators and the ash trees have no natural defenses.

EAB was first discovered on the North American continent in Southeastern Michigan in 2002, likely brought in with wood packing material. Since its introduction, it has caused catastrophic tree deaths and slowly spread across the continent.

EAB has likely already been in our area for a few years; the amount of time that it takes for a healthy ash tree to die from EAB is 3-5 years, that is why we are seeing some of the first trees in active decline right now.

Ash trees make up 5% of Portland’s street tree canopy (1 in every 20 trees!) and there are 9,000 ash trees on streets and in parks of Eugene (with many more that haven’t been inventoried). In certain areas the absence of ash will be more stark than others. We will particularly notice ash trees dying in large numbers in certain natural areas (the Oregon Ash, Fraxinus latifolia) and in parking lots, where they are a popular landscaping tree. It is important to know that preemptively removing ash trees in large numbers will not stop EAB. The ash trees we have, as long as we have them, provide tremendous benefits to us and our environments

In response to the EAB’s arrival, some Friends of Trees staff members are taking trainings, doing research, and formulating our best response to the EAB presence in our community.

“We have a huge community of people with tree knowledge,” says Green Space Specialist Harrison Layer. “If we can accurately take notice of trees in distress, we can make a difference.”

What we can do:

  • Learn how to identify an ash tree.
  • Destroy ash trees that have died from infestation.
  • Give insecticide treatment to ash trees of distinction, important members of our community.
  • Plant a diversity of species in their place.
  • Find ash trees who do not succumb and appear resistant to Emerald Ash Borer, scientists need to know about these survivors with important genes!

“It gives me hope to think about finding trees that are resistant to EAB,” Harrison says. “It helps me imagine a future where we still have ash trees.” The USFS Dorena Genetic Resource Center south of Eugene has successfully bred disease resistance to blister rust in sugar and western white pines, and to Phytophthora lateralis for Port-Orford-cedar, giving hope for resistant strains of OR ash.

There are several natural predators of EAB, and EAB will likely cause a boom in native wildlife that eats EAB. Many birds, especially woodpeckers eat EAB larvae and pupae, and some native wasps have been documented to eat EAB larvae. Woodpecker activity on an ash is a hint that it could be infested with EAB. Sometimes blonde patches of sloughed off bark can be seen on the tree from woodpeckers, because EAB makes eating trails in the sapwood right under the bark surface.

EAB doesn’t infest ash trees less than 1-inch in diameter, meaning the ash we have planted in the Green Space Program the past couple planting seasons are immune for now.

Ash trees in decline will often feature defoliation from the top of the tree, epicormic growths (suckers from base), and have ‘D-shaped holes’ in their trunks. It is important to remember that the actual beetle can only be seen during its ‘flight period’ which is roughly between June 1st and August 30th.

“There are many green beetles that are native to Oregon,” Harrison says. “So it’s really important to correctly identify the EAB Beetle.”

While an EAB has the ability to travel up to 50 miles in flight, it doesn’t usually travel more than 10 miles in a year; furthermore, they typically settle on the next ash tree that they find, which is often much less than 10 miles away. It will take decades before EAB run out of food in our region.

Again, it is important to know that removing ash trees in large numbers will not stop EAB. The ash trees can still provide tremendous benefits as long as we have them. We will need to monitor the situation as long as we can to learn, adapt, and hopefully one day recover.

Other resources:

Tree Care

Leaflet – Watching the Seasons Change

You’re not the only one who’s noticing that the days are getting shorter. Our trees are noticing, too, and they’re taking it as a sign that the growing season is over. How do they notice? A hormone response is triggered by the shorter daylight hours, the angle of the sun, the cooler temps. This past month, you may have noticed a spring-like flush of herbaceous growth on your trees—one final push before autumn. That new growth will harden into woody material tough enough to survive our first frost in November.

Leaves on some deciduous trees will start changing color, a welcome sign of the cooler seasons after an especially hot summer. In a process called abscission, trees reabsorb the nutrients stored in the leaves before detaching and shedding them. Chlorophyll, which gives leaves their green color, is one of the first things to be absorbed, which is why we see them change color. But fallen leaves still have plenty of nutrients, which is why we encourage you to leave the leaves. Trees are putting those leaves there on purpose, to enrich the soil for their roots.

Most deciduous trees shed leaves in the fall. Some don’t though! Scarlet oaks, swamp white oaks, and many evergreens shed leaves in the spring as new growth emerges

For now, the best thing we can do is watch the weather, just like our trees are. Continue your watering regime until we’ve had one inch of rain in a week. After that, we’ll be out of the dry season and beyond the growing season when trees actively expand their canopies as they photosynthesize. And it happens to coincide with the timing for our trees to transition into winter dormancy, when their sap returns to their roots.

Roots can grow year round in the right conditions—moisture, air, and temperature—which is why we plant when we do, so trees can focus on establishing their roots. To help keep those conditions right for your young tree, make sure you replenish your mulch in the next couple months. One inch of mulch is a windbreaker, three inches is like a down jacket – and we want that year round, protecting against temperature extremes. Tree roots can grow 365 days a year as long as they have some moisture and a moderate soil temperature, both things that mulch provide.

This time of transition can be really exciting. It’s always remarkable to feel like summer is barely over, but by Halloween, which is now right around the corner, most of our trees will be dormant. As the seasons change, so do the needs of our young trees. So watch the weather, and stay tuned to Treemail for best practices for each season!

Tree Care

Leaflet: Aphids

Aphids are everywhere, but don’t worry!

We’ve been getting a few inquiries about aphids this summer. And with the arrival of the emerald ash borer (a devastating issue we’ll keep you posted on), we have plenty of reasons to keep an eye out for pests. In the case of aphids, however, we don’t need to fret about them on our trees like we do in our veggie gardens.

In almost all instances, you don’t need to take any action—the tree can take care of itself. Aphids will only make a noticeable impact if the tree is still working to establish itself, or is somehow otherwise weakened. We often see them on Oregon ash, like the one pictured. If some wilting or crinkled leaves have you worried, here are some action steps you can take. Some folks might want to go straight to spraying, but pesticides really aren’t necessary to deal with aphids.

If you have more than just a few aphids on your leaves, the first thing to try is to just rinse them off with water. A good hose down will take care of a minor infestation. If that doesn’t quite do the trick, you can spray with soapy water. A treatment like this just once or twice a year will be enough.

If you see any ladybugs alongside the aphids, that’s great! Ladybugs will eat the aphids, and their larvae will really go to town feasting on them.

Aphids are everywhere—there are even tiny ones floating in the air we breathe. Some trees, like littleleaf linden, will have so many aphids that you may feel a mist of aphid “honeydew” when you walk underneath. You guessed it, that’s aphid poop. Just think of it as a nice reminder that trees are part of a larger ecosystem of living things.