The new year is in full swing and as the winter weather ebbs and flows, Denver will continue to see freezing temperatures, flurries of precipitation and snowstorms potentially as often as we see sunny, 60-degree days. We caught up with the smart folks at Denver Parks and Recreation’s forestry office to discuss the best methods for winterizing the trees in your yard. For insight and expertise on how to protect your trees from Denver’s highly variable winter months, read on.
How should a homeowner protect a tree during the winter months? Place mulch around the base of the tree, about three to four inches from dripline to dripline, if not three to four inches. Leave a three-inch gap from the edge of the mulch to the stem of the tree. Because we have warm winter days in Denver, too, watering your tree in the winter is also essential. Flood irrigation around the tree when daytime temperatures reach 45 degrees or higher (if the drip line lacks residual snow cover). In Colorado, winter watering months are typically November to February. Regardless of the age of the tree, this advice applies across the board.
Is there an ideal timeframe that Colorado homeowners should have their trees pruned each year? Pruning can be done at any time. The dormant season is best for pruning, especially for fruit trees, but homeowners who do their own pruning should wait until they can determine the difference between live and dead material. Always hire a professional if you’re unsure. However, American elms and any tree in the rose family (crabapples, pears, plums, cherry, apple) should be pruned during the winter months. Fruit trees should also be pruned in the winter months to avoid the spread of fire blight. Pruning maple and walnut trees during winter months is not ideal because they will bleed sap from the pruning cuts.
Should people expect a certain level of damage to their trees during the winter or can it be entirely prevented? Winter damage can be avoided if trees are regularly watered and properly mulched. Damage can occur in what we describe as “heavy load events” – a lot of snow breaking limbs – or a quick hard freeze, especially common for conifer trees. We saw this happen recently in October 2019 because of the two freezing nights.
When discussing winter damage, the term “dieback” comes up fairly often. What is dieback? Dieback is a condition in a plant in which branches or shoots die from the tip inward; caused by many conditions, but particularly a drought condition if they are not properly watered.
If branches break in a snowstorm, what’s the best use of those that have fallen or broken? We advise mulching them and re-using that material in your landscaping, flower beds and even around the base of your trees by chipping material using a brush chipper. Alternatively, Denver’s Department of Transportation & Infrastructure (formerly Denver Public Works) collects a limited amount of branches. These must be no larger than four inches in diameter, and they must be cut into lengths of four feet or less, bundled and tied, and weigh no more than 50 pounds. Customers may set out up to 10 bundles of branches on their scheduled every-four-week extra trash collection. Denver residents can also drop off branches at the Cherry Creek Recycling Drop-off center.
Do you have any other tree winterizing tips? For young trees wrap the trunks each year with tree wrap, until the bark develops furrows. This is especially important with thin-barked species such as honey locust, maple, linden and fruit trees. Starting at the base, wrap the trunk covering each turn about 30% up to the first branch union of the canopy to protect them from the intense sunlight.
Once again, we’re excited
to partner with our friends at Denver Public Works, Denver Recycles and Ace Hardware to give away FREE 5-packs
of compostable 30-gallon paper leaf bags to help Denver residents keep leaves
out of landfills!
Unlike plastic bags, these brown
paper bags can be composted along with the leaves; saving time and reducing
plastic waste in our landfills. This fall, Be a Smart Ash and compost your leaves.
Halloween is upon us! Do you know what’s spooky? Zombie trees.
Zombie trees are those that are still standing upright but are dead inside from a variety of environmental factors; disease, insect infestation, improper pruning and lack of water. They might look alive but these ticking time bombs will eventually topple over, posing a real danger to both the public and your property. If you have a zombie tree, a strong wind could easily send it toppling over and cost you thousands of dollars in damages – to your yard, roof, vehicles or wherever it may land.
Symptoms of a zombie tree:
that is decaying, missing or showing breakage
and/or falling branches
we have early fall snows and high winds in Colorado, Denver residents should
always be mindful of the health of the trees on their property,” said Sara
Forestry Program Manager in the Office of the City Forester.
you live in Denver and own property, you are responsible for:
Cleanup of debris from trees on private property and from trees within the public right-of-way adjacent to their property. (Limbs on the ground are considered debris. Property owners can hire any company to haul limbs away – for this type of work, the company does NOT have to be a licensed tree contractor.)
Pruning needs of private property trees and trees within the public right-of-way adjacent to your property.
Unfortunately, there are times when the
safety of the public necessitates that the work be completed immediately and
Denver Forestry cannot allow time for the property owner to find a licensed tree professional. When a
tree or limb is blocking safe access to the street or right-of-way, Denver
Forestry has an on-call contractor remove the limb or tree and bills the
property owner for the work.
As pumpkin spice lattes make their debut at our local coffee shops, so do the colors of fall. The leaves of trees in our parks and backyards are beginning to change from green to yellow, purple and plum – a clear sign that winter will soon be here.
Take advantage of these vibrant signs and Be A Smart Ash. With the Emerald Ash Borer confirmed in the City of Westminster, directly neighboring the City of Denver to the west, now’s the time to Be A Smart Ash. Use the vibrant fall color change as your guide and get outside; look for the most colorful leaves, then use these telltale identifiers to confirm you’ve found an Ash:
Compound leaves: A simple leaf is defined as a single leaf that has a bud at the base of the leaf stem. Conversely, a compound leaf (the sort you’re looking for) is defined as having more than one leaflet per leaf connecting to a stem that has a bud at its base. Ash tree leaves typically have 5-9 leaflets per leaf.
Opposite branching: By opposite branching, we mean the branches protruding from tree limbs have a mate protruding from the exact opposite side of the same limb. Only ash, maple, dogwood and horse chestnut trees have opposite branching.
Diamond-pattern bark: While this identification method may not be as helpful when it comes to young ash trees (they typically have smoother bark), the bark on more advanced ash trees tends to have distinct diamond patterns.
Once you’ve confirmed the tree is an Ash tree, make sure you don’t see any pesky green bugs around, or any wavy trail lines or d-shaped holes in the trunk. Multiple visuals can be found here. Hopefully, the tree is healthy, in which case there are multiple options to help keep it that way.
Smart Ash Superhero is making the rounds to local libraries, recreation centers
and public spaces to introduce more Denverites to the Emerald Ash Borer (EAB)
and ways to Be A
Smart Ash. Be on the lookout for the Smart Ash display and let us
know where you see him by tagging @BeASmartAsh or using the hashtags #EAB and
#BeASmartAsh on Twitter.
our effort to save Denver’s ash trees by talking to your neighbors, friends and
co-workers about EAB and encourage people to visit BeASmartAsh.org
for more information.
Emerald Ash Borer (EAB) was confirmed in the City and County of Broomfield,
northwest of Denver, on Aug. 20, 2019 – the first confirmation of EAB in
Colorado outside of the federal quarantine that primarily encompasses Boulder
Broomfield resident familiar with the appearance of EAB due to Broomfield’s
proactive public education campaign noticed a suspicious insect on their
personal property near 136th Avenue and Main Street and contacted
the Broomfield city forester. It is not known whether the pest arrived by
natural spread or human transport such as firewood.
least 15% of all urban and community trees in Colorado are ash species
susceptible to being killed by EAB. EAB attacks and kills both stressed and
healthy ash trees and is so aggressive that trees typically die within two to
four years after infestation. While EAB has not yet been detected in Denver, it
could already be here.
Austin Troy is Professor and Chair of the Department of
Planning and Design at the University of Colorado Denver. As part of the Master
of Urban and Regional Planning (MURP) faculty, Troy is one of the most
respected researchers in the planning field. The Smart Ash team recently caught up with him to discuss
sustainable urbanism and tree and lawn care during the hot summer months.
would you explain sustainable urbanism and regional sustainability to the
sustainability is a field of study that examines the interaction of social and
environmental systems in cities. I mainly work with green infrastructure – including
mapping the location of trees and vegetation, prioritizing where they should be
planted, and characterizing their many benefits to the city. As for regional
sustainability, I like to point to the Green Building
ordinance as an example. City voters passed this initiative in
2017 and it’s the most aggressive greening ordinance in the country right now.
your opinion of Denver’s current tree canopy?
very impressive and vast when you consider how much the city has grown in the
past century. Much of the current canopy can be attributed to decisions that
were made 70 to 100 years ago by Mayor Speer and other Denver leaders.
homeowners, the million-dollar question is (water time slots and allocations notwithstanding)
how much should you water your lawn? How do trees affect water needs?
Answer: Nobody quite understands this and the short answer is that it’s complicated. Tree shade is really important to overall irrigation demands. My team is in a partnership with Denver Water and when we look at their data we see that people who have mature tree canopy over grass can theoretically use less water in many cases than those with only grass. Broadly speaking, shade can offset your water costs. This may be because lawns without tree shade can get desiccated in the direct sun and homeowners try to compensate by overwatering. That said, we also think older trees are tapping into some of Denver’s older clay pipes for water. It’s a leaky infrastructure. Also, as people water their lawns, much of that water goes back into groundwater where more mature trees with deeper roots can reach it. There are a lot of factors to consider.
type of treatment or care should a healthy tree receive in the summer months?
always wise to lean on an experienced arborist for
this guidance. It depends on the species but most need to be pruned. Younger
and smaller trees often require more water.
is your team currently working on?
Answer: We’re heavily
researching the benefits and the costs of trees and vegetation in Denver. We’re
interested in a wide suite of things, ranging from heat mitigation to storm-water
mitigation to rainfall interception to socioeconomic factors like crime and
property values. The goal is to provide the tools to help ensure that the
benefits of trees are fairly and equitably distributed throughout Denver.
are you up to in your own yard?
Answer: I recently hired a landscape architect to help me bring my vision to life. Up until now I had just been maintaining my yard and not thinking outside the box. Now I want to introduce more native, low-water plants and interesting landscape features. Hopefully, there will be a lot less space that requires irrigation. I’m excited about it!