Trees serve many important functions on the planet. And of course we love trees and want them to thrive. But knowing how to properly select, plant, care for and prune them is not always intuitive.
This point was brought home to me over the weekend while traipsing around with a group of arborists and tree care professionals, in town for the 2012 International Society of Arboriculture Annual International Conference, Trade Show and Tree Climbing Championship, held this year in Portland. Gathered in Portland over the next few days are tree researchers, urban planners, certified arborists, and others on the cutting edge of research and experimentation in the field of arboriculture.
Our group toured three important tree planting sites around the city, observing both what worked and what didn’t. I was reminded of the important role trees play in the life of a city, as well as to individual people and gardeners.
It also reminded me that proper tree care is not common knowledge. In addition to cutting-edge tree-planting projects, I witnessed examples of stressed, sick, badly-pruned, poorly tended and neglected trees on Portland’s streets. Some tree education is in order for our citizenry!
Of the three projects our tour group visited, the most ambitious was the tree-planting along a 16.5-mile I-205 Multi-Use Path running from the Columbia River south to Gladstone. This joint project by Friends of Trees, Metro, the Oregon Department of Transportation and other private and non-profit organizations and donors planted about 3,600 trees in the past three years).
The trees were planted largely by volunteers who, in the process, learned the basic skills needed to plant trees properly. Community tree-planting projects run through much of the winter in Portland and anyone can join in and gain (free) experience learning how to do it right. And through programs like the Neighborhood Tree Stewards program, citizens can learn how to maintain and prune trees, too. It’s a great program for anyone wanting to learn more about trees, directly from experts whose knowledge is research-based, not merely apocryphal.
The plantings in the I-405 corridor consist mostly of native trees and shrubs, which will provide huge benefits in the years to come. Those benefits include improving air quality for residents and commuters in the polluted I-205 corridor, as well as helping mitigate global warming with expansive tree canopies, absorbing storm water runoff, providing wildlife habitat and providing a soothing green oasis for drivers and all users of the I-205 multi-use corridor. These are the same benefits that result from planting trees anywhere, including on parking strips in the city. But this huge project involved a massive amount of collaboration and work on the part of the involved governmental, private, non-profit and volunteer organizations and businesses, drawing attention from all over the US. It made me proud of Portland! We aren’t perfect, but we’re working on our urban forest with uncommon commitment, and it’s getting better all the time.
Good tree planting and care resources include the International Society of Arboriculture/Trees Are Good website and our own Friends of Trees. And even though it is the worst possible time to plant a tree right now in the Portland area, it is a great time to take a close look at any recently-planted trees you may have, and water, weed and mulch.
Water. Early and deep watering is critical to the health of trees, especially during the period of initial establishment (the first three years). Infrequent watering stresses trees, putting them at risk of insects and diseases, stunting their growth and preventing roots from growing properly. The general rule is: 10-20 gallons of water per week (depending on the size of the tree). Friends of Trees sells ooze tubes – plastic drip irrigation bags designed to help gradually water trees. You can also take a large plastic pail and punch a small hole in the bottom so that when you fill it, it only slowly oozes out.
Weed. Keep grass away from the base of young trees – at least 18" diameter from the trunk will do, although more is better. There are many reasons for this, including the fact that grass and weeds pull nutrients and water away from young trees. Another benefit to keeping grass away from the trunk is that you keep weed-whackers and mowers away from the tree’s trunk. Bark damage caused by mowing equipment leads to gradual tree death.
Mulch. Apply one to three inches of woody mulch around the trunk (but at least an inch away from the trunk itself) for the first three years minimum. Woody mulch helps retain moisture in the soil and gradually improves the soil beneath, as well as suppressing the growth of grass and weeds.
Even if your trees were planted more than three years ago, there’s a good chance that the very dry, windy weather we’re having right now is causing them stress. Watering can help even established trees make it through our dry summers. Exceptions to the watering rule: if your trees are from a winter-wet/summer-dry climate (ie, drought-tolerant trees like madrone or California live oaks, for example), then you can skip the watering part. Summer water can actually be harmful to some trees hailing from summer-dry climates.