Regional guide

Walla Walla Inland Northwest Vegetable Garden

WSU Walla Walla County guide for Inland Northwest frost-free timing, microclimates, soils, sun, temperature, and watering.

Climate signals

• The WSU Walla Walla County Inland Northwest Climate and Soil section says the frost-free season is usually between May 15 and September 15.
• The frost-free season varies from year to year, and the Inland Northwest has many microclimates.
• Soil pH is generally neutral, ranging from 6.5 to 7.5, and soils can range from heavy clay loam to very sandy, sometimes in the same yard.
• Vegetables do best in full sun with a minimum of 6 hours, but leafy vegetables such as lettuce and spinach can grow in partial shade.
• Morning sun only may be sufficient for beets and carrots, and good drainage is necessary.

Planning notes

• Cool season vegetables can germinate in soil temperatures as low as 40F and mature during cool spring and early summer weather.
• Broccoli, Brussels sprouts, and cabbage need to be started early indoors or purchased as transplants to mature before hot weather.
• Warm season vegetables are damaged by frost, cold nights, and cold soil; they need warm soil of at least 60F and long warm days to mature.
• Early varieties are best suited to the shorter gardening season of the Inland Northwest.
• The WSU schedule says March 1 indoors: start cabbage, cauliflower, broccoli, Brussels sprouts, tomato, and pepper seeds; April 1 to 15 indoors: start tomato and eggplant seeds.
• The April 15 to May 1 outdoor window includes beets, carrots, turnips, lettuce, spinach, chard, peas, radishes, potato pieces, and brassica transplants.
• The May 15 to June 1 outdoor window includes beans and corn with a replant warning if frost occurs, plus cucumbers, melons, squash, tomatoes, peppers, and eggplant transplants.
• The June 1 to June 15 outdoor window includes okra seeds, carrots, and tomatoes, peppers, and eggplant transplants.
• Most vegetables need at least an inch of water a week, and hot and windy conditions can require additional watering.
• Organic mulches should wait until the soil has warmed, about June 1, and young seedlings should not be mulched until they are six inches tall.
• Do not plant the same crop or family of crops in the same place two years in a row.
• Potatoes, onion sets, Jerusalem artichokes, asparagus crowns, and rhubarb roots are source rows without priority links; use priority catalog links as crop-row examples, not WSU cultivar recommendations.

Catalog crop examples

These catalog entries match crops covered by the regional timing source; variety-specific details remain tied to each seed entry's own source.

• Provider Bush Bean Vegetable · Warm · 50 days
• Detroit Dark Red Beet Vegetable · Cool · 58 days
• Waltham 29 Broccoli Vegetable · Cool · 74 days
• Long Island Improved Brussels Sprouts Vegetable · Cool · 100 days
• Golden Acre Cabbage Vegetable · Cool · 64 days
• Danvers 126 Carrot Vegetable · Shoulder · 70 days
• Snowball Y Cauliflower Vegetable · Cool · 70 days
• Bright Lights Swiss Chard Vegetable · Shoulder · 55 days
• Golden Bantam Sweet Corn Vegetable · Warm · 80 days
• Marketmore 76 Cucumber Vegetable · Warm · 58 days
• Black Beauty Eggplant Vegetable · Warm · 80 days
• Black Seeded Simpson Lettuce Vegetable · Cool · 45 days
• Hale's Best Jumbo Melon Vegetable · Warm · 85 days
• Clemson Spineless Okra Vegetable · Warm · 56 days
• Sugar Snap Pea Vegetable · Cool · 62 days
• California Wonder Pepper Vegetable · Warm · 72 days
• French Breakfast Radish Vegetable · Cool · 28 days
• Bloomsdale Spinach Vegetable · Cool · 42 days
• Waltham Butternut Squash Vegetable · Warm · 95 days
• Roma Tomato Vegetable · Warm · 76 days
• Purple Top White Globe Turnip Vegetable · Cool · 55 days

Related regional guides

• Washington West of the Cascades Vegetable Garden WSU Extension guide for western Washington gardens where cool springs, rainfall, and mild winter microclimates shape vegetable planning.

Source: WSU Walla Walla Inland Northwest Vegetable Gardening