Washington Planting Guide: What to Grow and When

Gardening in Washington state means working with one of the most varied climates in North America. From the rain-soaked lowlands west of the Cascades to the sun-drenched vineyards of the Yakima Valley, a single state encompasses USDA hardiness zones 4 through 9—a span that would take you from Minnesota to coastal Georgia if you traveled south along the East Coast. That diversity is both Washington’s greatest gardening challenge and its greatest opportunity.

This guide cuts through that complexity. You’ll find precise frost date tables by city, a month-by-month planting calendar, a curated list of top performers for both sides of the mountains, and practical advice drawn from Washington State University Extension’s decades of Pacific Northwest research. Whether you’re nursing seedlings under grow lights in Olympia or coaxing melons to ripen in Kennewick, the information here will help you plant at the right moment and grow what actually thrives where you live.

Understanding Washington’s Climate Regions

Before you can plan a planting calendar, you need to know which Washington you’re gardening in. The Cascade Range splits the state into two fundamentally different growing environments, and treating them as interchangeable is the most common mistake new Washington gardeners make.

Western Washington (Zones 7–9)

West of the Cascades, the marine influence dominates. Winters are mild and wet, rarely cold enough to kill established perennials. Summers are warm and increasingly dry as the season progresses—the famous Seattle drought that surprises newcomers every July. The growing season is long but defined by cool temperatures rather than heat accumulation. This means brassicas, root vegetables, and leafy greens are superstar performers, while heat-loving crops like melons and peppers struggle unless you choose specially adapted short-season varieties or use season extension tools.

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Key cities and their approximate zones: Seattle (Zone 8b), Olympia (Zone 8a), Bellingham (Zone 8a), Tacoma (Zone 8b), Everett (Zone 8a).

Eastern Washington (Zones 5–7)

Cross the Cascades and the climate flips. Eastern Washington gets less than 8 inches of rain annually in many areas, summers are hot (Yakima averages over 60 days above 90°F), and winters are genuinely cold. Frost arrives early in fall and lingers into spring. But those hot, dry summers are exactly what corn, melons, winter squash, and stone fruits need to develop full sweetness. The Yakima Valley produces over 70 percent of Washington’s apple crop for good reason: the climate is nearly ideal for them.

Key cities and their approximate zones: Spokane (Zone 6a), Yakima (Zone 6b), Tri-Cities (Zone 7a), Wenatchee (Zone 6b), Walla Walla (Zone 7a).

Washington Frost Dates by City

Frost dates are the anchor points of any planting calendar. These figures represent the 50 percent probability dates from NOAA historical data—meaning there is roughly a 50 percent chance of frost on or before the last spring frost date and on or after the first fall frost date. For frost-sensitive crops, use the 10 percent probability dates (roughly 2–3 weeks later in spring, 2–3 weeks earlier in fall) if you want greater confidence.

Notice how dramatically the dates shift between western and eastern Washington. Seattle gardeners have nearly twice the frost-free days of Spokane gardeners and can start many crops outdoors weeks earlier. Consult the WSU Extension Gardening in Washington resources for county-specific data, particularly if you garden at elevation or in a frost pocket.

Washington Planting Calendar

This calendar reflects conditions for western Washington (Puget Sound lowlands). Eastern Washington gardeners should shift direct-sow dates 4–6 weeks later for spring and 2–3 weeks earlier for fall, and move transplant dates accordingly. “Start indoors” means seed-starting under lights or in a heated greenhouse.

This calendar is a starting point. Your specific microclimate—a south-facing slope, a frost pocket, an urban heat island, a windbreak from tall trees—can shift these windows by several weeks in either direction. The year-round planting guide provides a deeper look at monthly timing across all seasons if you want to fine-tune your schedule further.

Best Vegetables for Western Washington

Western Washington’s cool, moist climate is genuinely exceptional for a specific set of crops. Lean into these and you’ll consistently out-produce gardeners in sunnier but hotter climates.

Brassicas (Cabbage Family)

Kale, broccoli, Brussels sprouts, cauliflower, cabbage, and kohlrabi are perhaps the single best investment for a western Washington garden. These crops not only tolerate cool temperatures—they actively improve in flavor after frost, which concentrates sugars in their leaves and stalks. Kale planted in September will produce through winter and into the following spring without protection in most Puget Sound lowland gardens. Choose overwintering varieties like ‘Daubenton’s Kale,’ ‘Red Russian,’ or ‘Lacinato’ for year-round production.

Root Vegetables

Carrots, beets, parsnips, turnips, and celeriac all perform exceptionally well in western Washington’s cool, deep soils. Carrots sown in late summer will size up slowly through fall and can be left in the ground under straw mulch for winter harvest—the sweetest carrots you’ll ever taste. Parsnips need a long season (plant in May for fall harvest) but require no maintenance and are nearly indestructible once established.

Alliums

Garlic planted in October and overwintered produces dramatically larger bulbs than spring-planted garlic in most climates. Start onions from seed indoors in January for large bulbs by late summer. Leeks are another outstanding performer—sow in February, transplant in May, and harvest from September through February the following year.

Peas and Fava Beans

Peas sown directly into the ground in late February to early March will come into bearing just as temperatures warm enough to be comfortable in the garden—a perfect pairing. Both snow peas and shelling peas do beautifully. Fava beans, planted in October for overwintering, are one of the most productive crops possible in western Washington: they fix nitrogen, provide early-spring greens, and yield heavily before summer heat causes them to decline.

Tomatoes in Western Washington

Tomatoes are achievable but require strategy. Choose varieties bred for cool summers: ‘Stupice,’ ‘Siletz,’ ‘Legend,’ ‘Black Prince,’ and ‘Early Girl’ consistently outperform large beefsteak types. Grow against a south-facing wall or fence to capture reflected heat, use black plastic mulch to warm the soil, and consider a simple cloche or cold frame until late May. Late blight (Phytophthora infestans) is endemic to the region; grow resistant varieties and ensure excellent airflow between plants.

Best Vegetables for Eastern Washington

Eastern Washington’s hot summers and reliable sunshine create ideal conditions for crops that struggle west of the Cascades. The tradeoff is a shorter frost-free window and the need for irrigation, but the crop quality in peak season is outstanding.

Corn

Sweet corn reaches its full potential in eastern Washington, where July and August temperatures regularly hit the 90s°F that corn needs to develop deep sweetness. Direct sow after May 1 (Yakima) or May 15 (Spokane) into warm soil. Plant in blocks of at least four rows for good pollination. Bi-color and yellow varieties like ‘Honey Select,’ ‘Bodacious,’ and ‘Ambrosia’ all perform excellently.

Melons and Watermelons

The Tri-Cities area and Yakima Valley can produce exceptional cantaloupe and watermelon with the heat units available. Start indoors 3–4 weeks before transplant date, use black plastic mulch to maximize soil temperature, and choose shorter-season varieties: ‘Crimson Sweet,’ ‘Sugar Baby,’ and ‘Ambrosia’ cantaloupe ripen reliably in most eastern WA locations. Give plants at least 3 feet of spacing and water consistently at the base—overhead irrigation increases disease pressure significantly.

Winter Squash and Pumpkins

Butternut, delicata, and acorn squash all ripen to perfection in eastern Washington’s long, hot summers. The dry air drastically reduces the powdery mildew that plagues squash west of the Cascades. Direct sow after May 15 or start indoors 2–3 weeks earlier and transplant once soil is warm. Cure harvested squash at 80°F for 10 days to harden the skin for storage.

Peppers and Eggplant

Start indoors in February and transplant after soil reaches 65°F (typically late May). Eastern Washington’s heat accumulation is sufficient for bell peppers, hot peppers, and eggplant to produce abundantly—something rarely achievable west of the Cascades without a greenhouse.

Top Plants for Washington Gardens

The following table summarizes the highest-performers across both sides of the state, with notes on which region they favor.

Seasonal Gardening Tips for Washington

Winter and Early Spring: January–March

Western Washington gardeners are never fully dormant. January is onion and leek seeding time under grow lights—the single most impactful act to get a head start on the growing season. Check overwintering crops (kale, chard, leeks, favas, spinach) and remove any diseased or slug-damaged material. February through early March, begin hardening off broccoli and cabbage seedlings started in January.

In eastern Washington, January through March is planning and equipment maintenance time. Seed-starting begins in earnest in February for onions and leeks, with tomato and pepper seeds following in the third week of February for transplanting to the garden around mid-May.

Spring: April–May

This is the most critical planting window in western Washington. Soil temperature in the Puget Sound lowlands typically reaches 45°F (the threshold for carrot and beet germination) by early April. Get peas, spinach, lettuce, arugula, kale, broccoli transplants, and root vegetables in the ground as soon as the soil drains and can be worked without compacting—usually late March in mild years, early April in cooler ones. Resist the urge to plant heat-lovers outdoors before May 15 in western WA.

Eastern Washington spring arrives sharply. April typically still carries hard frost risk in most locations. Focus April on indoor seed-starting for tomatoes, peppers, cucumbers, and squash. Direct sowing outdoors begins seriously after May 1 in the Yakima and Tri-Cities areas, and after May 15 in Spokane and the Palouse.

Summer: June–August

Western Washington summers are warm, dry, and ideal for harvesting—but not always for planting. The key summer task is succession sowing short-season crops (beans, beets, carrots, cucumbers) every 2–3 weeks to maintain continuous harvest. Begin fall-crop seed starting in July: broccoli, cabbage, and kale started indoors in mid-July will be ready to transplant in mid-August for a robust fall harvest.

Eastern Washington summer is harvest season for most major crops. Water management is the primary task—most vegetables need 1–2 inches of water per week, and the combination of heat and dry air means daily irrigation checks for container plants and newly transplanted starts.

Fall: September–November

Western Washington’s mild fall extends the harvest season dramatically. September and October are ideal for direct sowing spinach, miner’s lettuce, claytonia, and arugula for late fall and winter harvest. Garlic goes in mid-September through mid-November; plant in well-amended soil with good drainage. Cover crops—winter rye, crimson clover, phacelia—protect bare soil through winter and improve structure for the following season.

Eastern Washington gardeners race the clock in fall. The first hard frost can arrive in October in Spokane and the higher-elevation areas. Prioritize harvesting all frost-sensitive crops before mid-October, and mulch garlic beds and perennial herbs with 4–6 inches of straw to insulate roots through the cold winter months.

Washington-Specific Gardening Challenges

Slugs in Western Washington

Western Washington is slug country. The Pacific banana slug and introduced European brown slug are significant pests for seedlings and low-growing crops. The most effective organic controls are iron phosphate bait (Sluggo), copper tape barriers around raised beds, and nighttime patrols with a headlamp and scissors. Avoid overhead watering in the evening, which creates the moist conditions slugs prefer.

Late Blight in Tomatoes

Late blight (Phytophthora infestans) thrives in the cool, moist conditions of western Washington summers and can devastate an unprotected tomato planting within days. Grow blight-resistant varieties (WSU’s ‘Legend’ and ‘Willamette’ are specifically bred for Pacific Northwest conditions), ensure wide spacing for airflow, and consider a preventive copper fungicide spray if you have a history of blight in your garden.

Irrigation in Eastern Washington

Annual rainfall in much of eastern Washington is insufficient for a productive vegetable garden without supplemental irrigation. Drip irrigation is the most water-efficient system and dramatically reduces foliar disease by keeping leaves dry. Many eastern Washington counties have water rights considerations—check with your local extension office if you plan to install a large irrigation system.

Soil in Western Washington

Western Washington soils are often acidic (pH 5.5–6.0), which is ideal for blueberries but below optimal for most vegetables. Lime applications in fall help raise pH for the following season. Heavy clay soils common in many lowland areas benefit from annual additions of compost and are best worked when dry—tilling wet clay creates compaction that can persist for years.

Companion Planting for Washington Gardens

Pairing compatible crops can improve yields, manage pests naturally, and make the most of limited garden space—a particularly useful strategy in the densely planted cool-season western Washington garden. Classic combinations like tomatoes with basil, beans with corn and squash (the Three Sisters), or nasturtiums as aphid traps around brassicas all translate well to Washington conditions. The companion planting guide covers the mechanisms behind these pairings and flags combinations to avoid, including the documented antagonism between alliums and legumes that can suppress bean germination when garlic and peas are planted too close together.

Understanding Climate Zone Shifts in Washington

Washington’s USDA hardiness zones have shifted measurably over the past two decades. Parts of western Washington that were formerly Zone 7 are now mapped as Zone 8, and the warmest parts of the Yakima Valley have crept from Zone 6 into Zone 7 territory. This matters for decisions about perennials, fruit trees, and overwintering crops. Gardeners across the state are finding they can now successfully grow plants—citrus in pots that survive mild western WA winters, figs that fruit reliably in Yakima—that would have been marginal choices a generation ago. The broader context of climate zone migration explains how to read these shifts and adjust your planting decisions accordingly.

Frequently Asked Questions

When should I plant tomatoes in Washington state?

In western Washington (Puget Sound region), transplant tomatoes outdoors after May 15, once the risk of frost has passed and soil temperatures have warmed above 60°F. Growing against a south-facing wall, using black plastic mulch, and choosing cool-tolerant varieties like ‘Stupice,’ ‘Siletz,’ or ‘Legend’ dramatically improves success. In eastern Washington (Yakima, Tri-Cities, Spokane), transplant after May 10–15 when the soil is reliably warm—tomatoes perform much more easily there given the heat accumulation through July and August.

What grows well year-round in western Washington?

Kale, chard, spinach, miner’s lettuce, claytonia, leeks, and overwintering brassicas like purple sprouting broccoli can all be harvested through the winter months in the Puget Sound lowlands without any protection. Established rosemary, thyme, sage, and oregano typically survive winters intact west of the Cascades. Garlic planted in October is dormant through winter but actively growing by February.

What’s the easiest vegetable to grow in Washington state?

Kale is arguably the easiest vegetable to grow in western Washington: it tolerates frost, grows through mild winters, is rarely bothered by the most common pests (though aphids occasionally colonize new growth in spring), and produces over a remarkably long season. For eastern Washington, zucchini and summer squash are nearly foolproof given the hot summers—plant in late May and expect an abundant harvest from July through September.

Can I grow vegetables in eastern Washington without irrigation?

It is technically possible for a very limited range of drought-tolerant crops, but most vegetables require consistent moisture that eastern Washington’s 7–8 inches of annual rainfall cannot reliably provide through the growing season. Drought-tolerant herbs like rosemary, thyme, and lavender can establish without supplemental water once mature, but vegetable gardens in eastern Washington are not viable without irrigation. Drip systems are far more efficient than overhead sprinklers and dramatically reduce foliar disease risk in the dry, hot environment.

When do I plant garlic in Washington state?

Plant garlic in mid-September through early November across Washington—both sides of the Cascades. In western Washington, September through mid-October is ideal. In eastern Washington, September and early October are preferred, before hard freezes lock in the soil. Plant cloves 2 inches deep and 6 inches apart, pointed end up. Mulch with 3–4 inches of straw after the ground cools. Harvest when the lower leaves are brown and the upper leaves are still green, typically July in western WA and late June to early July in eastern WA.

What USDA zone is most of western Washington in?

Most of the Puget Sound lowlands (Seattle, Tacoma, Olympia, Everett, Bellingham) fall in USDA Hardiness Zone 8a or 8b. Some protected urban locations in Seattle and south Puget Sound have been mapped Zone 9a in recent USDA updates. Olympic Peninsula rain shadow areas (Sequim) are notably drier than the broader western WA pattern despite being in Zone 8. Use frost date data alongside zone information—zone only reflects average winter minimum temperature, not summer heat, rainfall, or frost timing.

Sources

• Washington State University Extension – Gardening Publications — WSU Extension is the primary research-based resource for Washington gardening, offering publications on vegetable production, pest management, soil health, and variety trials specific to Pacific Northwest conditions.
• USDA Natural Resources Conservation Service – Plant Hardiness Zone Data — The USDA NRCS provides the authoritative zone data and frost date probability tables used in this guide.