Hardiness zones are defined areas that specify the likelihood of certain plants growing well. The USDA hardiness plant zone map (see resources) divides North America into 11 zones. Zone 6 includes parts of Washington, Oregon (just a bit of California) and then it extends, primarily, eastward through the center of the U.S. The coldest temperatures in zone 6 are commonly between -10 and 0 Fahrenheit. When selecting plants for your yard, it's best to purchase those recommended for your particular zone.
This green perennial will apprise you of yellow-golden clumps of flower heads in the late summer and right through the fall months. Goldenrod is a good choice for zone 6 locations as it doesn't fall at the bottom of the recommended zones (5 through 9) for this plant. This allows for any unusual dips in winter temperatures. Goldenrod prefers a full-sun location in your garden. It will grow from 8 inches to 5 feet, depending on the variety. It's interesting to note that the pollen from this plant does not bother hay favor sufferers. Care for goldenrod by removing dead heads (dead flowers) and cut the foliage to ground level after the first frost in your area. It's a drought tolerant plant, making it perfect for high dessert in zone 6 locations or times of drought.
Old Garden Rose
The Old Garden Rose, sometimes referred to as antique or heirloom roses, are durable and have disease resistant leaves. The bush produces large, velvety blooms and prefers a full-sun location, as do most roses. This is an excellent zone 6 plant, with recommended zones 4 through 9. At full maturity the Old Garden Rose grows to a height of between 3 and 5 feet with a spread of between 3 and 4 feet. This summer blooming perennial does not need dead heading, but should be trimmed down to half it's size after summer blooming. When watering roses, refrain from wetting the leaves. Wet leaves may cause a fungus, despite it's resistance to other maladies.
The herb spearmint is a good choice for zone 6, with recommended zones 3 through 8. The luscious green spiky leaves adorn small lavender blooms. It leaves your garden smelling fresh, while it acts as an easy backdrop to brighter annual flowers. The plant will grow to 2 feet, or more, during the summer months. Spearmint is the most popular culinary mint, but even if you are not inclined towards kitchen activities, you can enjoy sprigs of this herb in your iced tea. Spearmint can be invasive. To eliminate this problem, plant the entire plant container into the ground, covering the pot lip. This will keep the roots from traveling to areas you had not planned.