Tropical Plants in Oregon
Located in Zone 8 on the U.S. Department of Agriculture Plant Hardiness Zone Map, Portland, Oregon shares the same zone as Tifton, Georgia and parts of Texas, but the climate is quite different. While temperatures in these areas do not traditionally drop below 10 F, Portland lacks the humidity of the south. It is, however, protected from coastal influences by the Coast Range of mountains. The growing season in Portland is about 275 days and rainfall is moderate.
Some tropical plants grow well in this area, however, winds may tear delicate leaves.
Bougainvillea (Bougainvillea spectabilis) is an evergreen, shrubby vine that can add color to any landscape and does well in Portland's temperate climate. Bougainvillea gets its color from the large bracts that surround the small white flowers the plant produces. These bracts may be vibrant magenta, white, crimson or yellow. The vine, which has a spiky stem, may be trained to grow up a trellis or wall.
Bougainvillea has fragile roots; be careful not to damage them when you plant bougainvillea. Cut the container off the plant, rather than pulling the plant out to protect the roots. Bougainvillea may be planted in full sun in Portland and requires moderate water once it is established.
Cannas (Canna) are tuberous-rooted perennials that are native to the tropics, but do well in Portland's temperate climate. Because the soil does not freeze in Portland, these plants may stay in the ground year round, but will die back in colder weather. Cannas grow on upright stalks, have leaves that resemble those on banana trees and a showy flower spike at the top. These plants spread quickly and may become invasive.
Best used in borders or in a grouping of multiple plants, cannas are available in a range of colors and sizes, including the Rover Bellflower (C. rapunculoides), a sturdy plant which does well in difficult soil and the Peach-Leafed Bluebell (C. persicifolia), which is available with blooms of blue, pink or white and grows to 3 feet.
Cannas should be planted in full sun and require ample water during the growing season.
Tree mallow (Lavatera arborea) is a tropical-looking plant whose bloom resembles the hibiscus, but is smaller. An evergreen shrub in Portland, tree mallow is easy-to-grow and provides a showy bloom in pinks, roses and whites throughout the summer. This plant, which can grow to 8 feet, has leaves that resemble maples.
The bicolor variety (L. maritima) has pink flowers of up to 3 inches with purple centers, while the L. thuringiaca variety has purple-pink flowers and blooms nearly year round.
Tree mallow should be planted in full sun and requires regular to little water.
- Texas A&M University Aggie Horticulture: Growing Bougainvillea
- Backyard Gardener: Tree Mallow
- "Sunset National Garden Book"; the editors of Sunset Books and Sunset Magazine; 1997