Portland’s mild climate offers a unique opportunity to enjoy green streets throughout the year, yet many urban areas are dominated by deciduous trees, leaving a bare and skeletal landscape during winter. While deciduous trees have their place, incorporating Evergreen Street trees can dramatically enhance the beauty and ecological benefits of our neighborhoods, even in the colder months. This article explores a selection of excellent evergreen street tree options, drawing from the insights of urban forestry experts, to help you choose the perfect trees for a vibrant, year-round green urban environment.
Discovering Hardy Evergreen Magnolias for Street Planting
Magnolias are renowned for their stunning flowers and elegant foliage. While Southern Magnolias are a classic choice, the urban forestry sector has expanded evergreen street tree options within this genus, introducing varieties that thrive in more northern climates.
Moonglow Sweetbay Magnolia: A Northern Evergreen Marvel
Magnolia virginiana ‘Jim Wilson,’ marketed as Moonglow, is a relatively recent introduction (2001) that brings the beauty of evergreen magnolias further north. This cultivar distinguishes itself by retaining its leaves more effectively than other sweetbay magnolias in colder regions and boasts an upright form, reaching about 35 feet tall with a spread of 18-20 feet. Its semi-elliptic leaves offer a delicate, non-leathery texture with a striking silvery white underside. Cream-colored, lemon-scented flowers appear in late spring and continue sporadically through the summer, adding to its appeal as an evergreen street tree. The glossy red seeds, clustered in cone-like formations, attract birds, further enhancing its ecological value. Moonglow’s smooth gray bark adds year-round visual interest, though it may take a few years to achieve a dense canopy, offering a lighter shade compared to Southern Magnolias. For those seeking a refined and resilient evergreen street tree, Moonglow Sweetbay Magnolia presents an excellent choice.
Edith Bogue Southern Magnolia: A Southern Classic Adapts to Northern Streets
Magnolia grandiflora ‘Edith Bogue’ is another Southern native that has proven its hardiness as an evergreen street tree even in cooler climates. While Magnolia grandiflora is famously the state flower of Mississippi and has been admired globally since the 1700s for its large, lemon-scented white flowers, not all cultivars are suited for colder winters. ‘Edith Bogue’, originally from Florida, stands out for its exceptional tolerance to snow and ice. Growing at a moderate pace to 30-40 feet tall and 15-20 feet wide, ‘Edith Bogue’ features lustrous, narrower leaves compared to the species, with a subtle brown indumentum underneath. Its late spring to summer flowering period and orange-pink seeds, attractive to birds, add to its seasonal interest. ‘Edith Bogue’ provides a robust and beautiful evergreen street tree option, bringing Southern charm to northern landscapes.
Evergreen Oak Street Trees: Durable and Diverse Choices
The oak family, surprisingly, includes numerous evergreen species. These oaks offer exceptional durability and diverse aesthetic qualities, making them ideal candidates for evergreen street trees.
Bambooleaf Oak: An Asian Evergreen Thriving in Urban Settings
Quercus myrsinifolia, the bambooleaf oak, originating from East Asia, is a standout evergreen street tree known for its attractive foliage and resilience. Native to regions including China, Korea, Japan, and parts of Southeast Asia, this oak has demonstrated remarkable hardiness in places like Portland. Its common name comes from its long, unlobed leaves, resembling bamboo. Bambooleaf oak exhibits rapid growth to 30-35 feet or more, forming a dense, round-headed tree with smooth, gray bark. New leaves emerge with a striking silvery purplish-red hue during the growing season, adding a touch of seasonal color, although it doesn’t have a typical fall color change. Specimens planted in recent decades have already reached impressive sizes and proven exceptionally tough, weathering ice storms and snowfalls with ease, solidifying its status as a reliable evergreen street tree.
Silverleaf Oak: Southwestern Resilience for Urban Streets
Quercus hypoleucoides, the silverleaf oak, hails from the southwestern U.S. and northern Mexico and brings drought tolerance and rapid growth to the selection of evergreen street trees. The tree’s common name is derived from the striking silvery undersides of its leaves. Silverleaf oak is noted for its fast growth, quickly developing into a densely branched tree reaching 40 feet or more. Its leathery, gray-green leaves contribute to its excellent drought tolerance once established. Examples in Hoyt Arboretum showcase its ability to thrive in both cold and heat when provided with ample sunlight. Silverleaf oak offers a robust and visually appealing evergreen street tree option, particularly suitable for drier urban environments.
Native Evergreen Broadleaf Trees: Embracing Local Options
Exploring native evergreen broadleaf trees provides ecologically sound and regionally appropriate choices for evergreen street trees, fostering local biodiversity and resilience.
Madrone: A Native Beauty with Specific Needs
Arbutus menziesii, the madrone, is a familiar native evergreen in the Pacific Northwest, known for its stunning exfoliating bark in shades of olive and ochre. Related to rhododendrons, madrone produces clusters of white, bell-shaped flowers in spring, followed by orange fruits that attract birds. However, madrone presents challenges as an evergreen street tree. It is difficult to transplant, requires well-drained soil and sunny locations, and is susceptible to diseases. While it can be a valued wildlife tree in suitable yard settings, its specific needs and transplanting difficulties make it less ideal for typical street tree planting.
Canyon Live Oak and Oregon Myrtle: Larger Native Evergreen Options
For larger evergreen street tree options, canyon live oak (Quercus chrysolepis) and Oregon myrtle (Umbellularia californica) offer native choices, though with considerations. Oregon myrtle (also known as California bay) can grow quite large (60-90 feet) and is drought and shade-tolerant. Its leaves have a strong, spicy aroma, which can be overwhelming to some (“headache tree”). It also tends to produce suckers and olive-sized fruits, potentially creating maintenance challenges. Canyon live oak, in contrast, is generally better-behaved in cultivation. While it can be shrubby in dry conditions, in good soil it becomes a stately tree reaching 60-80 feet. Its holly-like young leaves and acorns, historically a food source for Native Americans and favored by wildlife, add to its appeal. Canyon live oak’s deep taproot makes it drought-tolerant, but its size may be a consideration for narrower streetscapes.
Californian Evergreen Oaks: Expanding Hardy Street Tree Choices
California’s diverse flora offers additional evergreen oak species that are proving successful as evergreen street trees in regions with similar climates to Portland.
Interior Live Oak: Drought and Heat Tolerance for Urban Streets
Quercus wislizeni, the interior live oak, is notable for its exceptional drought and heat tolerance, thriving on as little as 15 inches of annual rainfall. While it can reach 70 feet, it is often shorter and develops a broad, densely branched form, providing excellent shelter for birds and animals. Its narrow, cone-shaped acorns, taking up to two years to ripen, are a food source for wildlife. The leathery leaves can vary in shape, adding textural interest. Interior live oak’s hardiness and adaptability make it a promising evergreen street tree for challenging urban conditions.
Blue Oak: Deciduous Tendencies with Evergreen Appeal
Quercus douglasii, the blue oak, is another Californian species with a unique characteristic. Its common name comes from the attractive blue-green color of its leaves. In colder Portland winters, blue oak may defoliate, but it reliably produces new leaves in spring. In milder winters, it can retain its leaves, offering near-evergreen street tree benefits in warmer years. Native Americans utilized blue oak extensively, highlighting its versatility. While not strictly evergreen in all conditions, blue oak presents an interesting option with seasonal greenery and notable hardiness.
Southern Live Oak: A Grand and Long-Lived Evergreen
Quercus virginiana, the southern live oak, is a truly majestic and long-lived evergreen street tree. Some specimens have survived for centuries, reaching heights of 60 feet with an even wider spread, providing ample shade. Its strong root system allows it to withstand harsh weather conditions, including hurricanes. The dark green, leathery leaves, lighter underneath, may drop in particularly cold winters but re-emerge in spring. Southern live oak’s longevity and grandeur make it a legacy evergreen street tree, suitable for spacious urban avenues.
Noble Laurel: An Aromatic and Functional Evergreen Street Tree
Laurus nobilis, the true bay laurel, offers both evergreen foliage and culinary benefits as an evergreen street tree. Native to the Mediterranean region, its aromatic leaves have been historically significant, used for wreaths in ancient Olympic Games. Bay laurel grows to 30 feet or more, with dense foliage, providing ample greenery. Its small yellowish flowers and black fruits attract birds. Planting bay laurel as an evergreen street tree provides a practical and aesthetically pleasing option, offering a readily available supply of culinary bay leaves.
Holly or Holm Oak: A Hardy and Long-Lived European Evergreen
Quercus ilex, the holly or holm oak, originating from the Mediterranean region and parts of Africa, is another hardy and long-lived evergreen street tree choice. Its Latin name “ilex” refers to holly, as young trees can have spiny leaves resembling holly, though this spininess lessens with maturity. Leaves are pale white underneath, and acorns are long and pointed. The bark is dark and fissured, adding visual texture. Holly oak can reach 60-80 feet and is known for its longevity, with specimens planted in England in the 1500s still living. Its resilience and historical longevity make it a remarkable evergreen street tree, though its potential for reseeding in natural areas should be considered.
The Importance of Evergreen Street Trees: Greening Our Winters
The dominance of deciduous trees in many urban landscapes, especially in regions with milder climates like Portland, creates unnecessarily bleak winterscapes. While deciduous trees are adapted to colder climates, Portland’s relatively mild winters and rainy season call for a greater emphasis on evergreen street trees. Deciduous trees lose their leaves just when we need them most – during the rainy season when foliage interception can help manage moisture and reduce flooding.
Planting more evergreen street trees is a straightforward solution to create greener, more vibrant urban environments year-round. While parklands often feature native evergreen conifers, city streets often lack this winter greenery. By increasing the proportion of evergreen street trees, we can improve the visual appeal of our cities, enhance ecological benefits throughout the year, and create more resilient and beautiful urban forests.
Urban Forestry initiatives are already promoting this shift by expanding the list of approved evergreen street tree options. By choosing from the diverse selection of hardy and attractive evergreen broadleaf trees now available, we can collectively transform our streets into year-round green corridors, enriching our urban lives and environments.
