The Pacific Northwest and, in fact, the entire western Cascade region running from Central British Columbia, through Washington and Oregon
and down into Northern California is blessed with a mild climate and abundant rainfall. This is great for growing lush perennial gardens, but the continual rain and the dense shade from native conifer trees make it hard to establish a new lawn. It can be done, though. By carefully preparing the soil, choosing the right type of grass, and planting the lawn at the appropriate time, you can make sure it’s your side of the fence where the grass is greener.
Planning the Pacific Northwest lawn
When choosing which grass species to plant, consider how you’ll use the lawn. You’ll need a more rugged variety of grass to stand up to ballgames and picnics than if you’re only planting a lawn for looks. Also, take a look at the shape of the area where you want to establish the lawn. Especially in the rainy Northwest, lawns should have a slight slope away from buildings or sidewalks to let excess water run off. A slope of anywhere from 1% to 6% is ideal. If you’re planting in a hilly Seattle neighborhood, though, keep in mind that while a slope of up to 12% is acceptable, any steeper and you’ll have problems with mowing and watering. For steep slopes, you can either regrade or opt for a hardy native ground cover like slender wintergreen (Gaultheria ovatifolia) or inside-out flower (Vancouveria hexandra) instead of lawn grass. While the lawn area might slope, the surface itself should be even. If there are low spots where rainwater could puddle, even them out before you plant.
Soil types west of the Cascades
Most lawn grasses prefer sandy loam soils that let water reach 8 to 12 inches into the soil. The silty loam soils of this region are also adequate for lawns, though. The black clay found in Oregon impedes drainage, but adding compost can take care of this problem. If you’re higher up in the Cascades, you may be dealing with decomposed granite, in which case you’ll have to add a considerable amount of organic material like topsoil and compost before much of anything will grow. Partly due to heavy rainfall leaching the soil, high pH (acidic) soils are common in the Pacific Northwest. Acidic soils aren’t the best for lawn grass and they also encourage moss and lichen, which are always ready to invade Cascade-area lawns. To find out if you’ll need to amend to soil to lower the pH or add minerals such as calcium, magnesium, potassium or phosphorus, have a soil test done by a local nursery or conduct one yourself using one of the kits available at gardening centers.
Type of grass for the Pacific Northwest
Most of the Pacific Northwest/Cascade region falls into USDA climate zones 8 and 9, with zone 7 starting in the Cascade foothills and zone 6 occurring higher up. The turfgrass map also used by some landscapers places the Pacific Northwest in the cool/humid zone. For these zones, the best choices are fine fescues like red fescue (Festuca rubra), along with certain bluegrasses and ryegrasses. Bentgrasses also grow well in the Northwest, but they require plenty of sun and regular maintenance. If you live near the coast, try “dwarf” tall fescues. Theses will need to be allowed to grow higher, but they offer a deep green color and tolerate salt better than most species. Buffalo grasses and zoysia grasses can also be grown in the Northwest, but they do better in the warm climates of southern Oregon and northern California. For warm microclimates, Bermuda grass is another possible choice.
As a rule, if you want to use your lawn for sports, choose rye; if it’s just for show, go with fescue. Fescues do well in sun, but still keep a healthy green color in the shady areas. Most ryegrasses need full sun to thrive, but they stand up to foot traffic better than fescues. In most cases, the ideal will be fine fescues such as creeping red or chewings mixed with ryegrass. The rye is useful because it sprouts quickly and offers coverage to prevent weed growth.
Don’t forget about native grasses, either. Because natives are adapted to local conditions, when planted in an appropriate site, they don’t need nearly as much watering or fertilizing as “imports.” Grasses native to the western Cascade region include Oregon bentgrass (Agrostis oregonesis), western fescue (Festuca occidentalis) and creeping red fescue (Festuca rubra), blue wildrye (Elymus glaucus), Alaska oniongrass (Melica subulata), and Columbia sedge (Carex aperta).
One grass to avoid in the Pacific Northwest is Kentucky bluegrass (Poa pratensis). Although popular in the north, most areas of the Northwest are too wet for this prairie grass. It does sprout quickly, though, so having a small amount in the seed mix will provide temporary coverage before the rest of the grass comes in.
Seed or sod?
Sod may seem like an easy route to an “instant lawn,” but for the long term, seed is a better choice. The roots of sod grass are likely to have been damaged by drying or contact with rough surfaces and this will affect the long-term health of the lawn. Another consideration for Northwest lawns is that most sod is primarily rye and Kentucky bluegrass, neither of which does well in this area. Sod is usually more expensive than seed and it’s more labor-intensive to plant than seed. For the healthiest lawn and fewer maintenance problems down the road, invest in the best, certified-quality seed you can find.
Pacific Northwest lawn planting times
West of the Cascades, spring is not a bad time to plant grass, but early autumn from late August through mid-October is better. If you’re at a higher altitude or planting fine fescues, try to get the seeding done in September. The reason for autumn planting is that there are fewer weed seeds waiting to sprout and the cooler temperatures make it easier to keep the new lawn moist. If your area receives frost, the grass will die, but the lawn will return again in spring.
Early spring from April to mid-May is also a good time to seed, provided you can keep the lawn well watered when the weather heats up. A new lawn should be kept moist for the first two months, so in particularly hot spring you may need to mist or water lightly every morning and late afternoon.
As the nationally famous gardens of Seattle and Vancouver, B.C. show, it is possible to establish a thick, green lawn west of the Cascades. If you’re planning to grow a lawn in the Pacific Northwest, check your soil type and amend as needed, choose a species of grass that’s appropriate for the climate, and you’ve already done half the work to ensuring a beautiful lawn for your home’s landscape.