As most Portland area residents know by now, trees are important contributors to healthy urban communities, providing us a vast array of benefits that include clean air, clean water, psychological well-being, even higher property values. While the warm months of June through September are not a good time to put new trees into the ground, it's still a good time to remind ourselves of another important tree-related benefit: lower energy bills as a result of cooling shade trees.
Temperatures near trees are cooler than that away from trees - and the larger the tree, the greater the cooling effect. By planting trees in our communities, we help moderate higher temperatures caused by the buildings and pavement in commercial areas. Shade trees provide a nice spot for a
picnic, and can shade our homes or cars, as well. Trees planted along our streets also have a cooling effect on paved surfaces, increasing the lifespan of blacktop while improving the curb appeal of a neighborhood.
For ideas about the best large (and a few medium-sized) trees to plant for shade and beauty, read on.
Bigleaf Maple (Acer macrophyllum)
As its name implies, bigleaf maple, an Oregon native, has the largest leaves of any maple. A great shade tree, bigleaf maple requires ample room. These trees get big - and wide - most can reach a height of 50' or more so give them plenty of room. Other pointers: don't top bigleaf maple (or any) trees, and protect bark from injury while young. You'll be rewarded with both summer shade and a little fall color.
Norwegian Sunset Maple (Acer truncatum x A.platanoides 'Keithsform')
This upright oval maple features particularly nice branch structure, dark green glossy foliage and attractive uniform canopy. It reaches an average of 35' in height and has good resistance to heat.
Fast grower, and good fall color.
Zelkova (Zelkova serrata 'Halka')
This is a good street and shade tree, a fast grower with a rounded crown and appealing vase-shaped form. Leaves are green to dark green in spring and summer, changing to ruddy
yellows, oranges and reds in fall display. Grows 50' - 80' high with a 50' - 75' spread. Prefers moist, well-drained soils and full sun; tolerant of wind, drought, and air pollution.
London planetree (Platanus x acerfolia)
These magnificent trees are superb shade trees. Whether lining a touristy boulevard in Rome, Italy, or shading a major thoroughfare in Corvallis, Oregon, they're popular for their attractive shade and interesting pale grey-green or buff-brown bark. Be forewarned: the "dust" they product
can trigger allergies; also, these trees get very big and must have adequate space for both roots and crown. Leaves are superficially maple-like and pleasing, and London Plane 'seed balls" attract squirrels, finches and other birds. These trees are tolerant to heat, drought, and pollution.
Horsechestnut (Aesculus hippocastanum)
These pretty ornamental shade trees have an upright-oval to rounded form, and can reach 50' - 75' in height. Leaves are light green as they unfold and turn dark green at maturity.
Horse-chestnut trees feature attractive, showy flowers, usually white, in erect panicles. Prefers roomy, moist, well-drained soil in full sun.
Katsura (cercidiphyllum japonicum)
This multi-stemmed ornamental tree features delicate heart-shaped leaves and bright autumn colors of yellow, pink, and orange-red. Fast growing, and they can reach 40 - 70 feet in height.
Sensitive to drought and likes deep, permanently moist soil.
For smaller yards
For a horsechestnut that will brighten the landscape but require a little less room, try the hybrid Aesculus x carnea, which will reach a height of just 30' - 40' and features red flowers. Another good choice: Red Rage Tupelo (Nyssa sylvatica 'Hayman's Red'), with its dark glossy green foliage and great, bright red color in the fall.
Before deciding which tree species to purchase it's always best to talk to your arborist, your favorite local nursery, or, hop on the internet and read up on the trees you're considering.
Lastly, if you've recently purchased a tree but haven't yet got it planted, you may want to wait for the cooler fall months of October or November to do so, as it will be easier to get established at that time. In the meantime, make sure it is well and regularly watered, and keep it in a place with
morning sun and afternoon shade, if possible.
For more tree care information:
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Cynthia Orlando has a degree in forest management and is a certified arborist with the Oregon Department of Forestry.