CORVALLIS, Ore. — Knowing when to plant vegetables can make the difference between a thriving garden and one that struggles all season.

Across Oregon — from the cool, wet coast to the dry high desert — weather patterns and soil temperatures vary widely, so timing is everything.

“One of the biggest mistakes people make is planting too early,” said Weston Miller, a former horticulturist with the Oregon State University Extension Service. “A few sunny days get people excited, but seeds can rot in cold, wet soil or germinate slowly. Even if they survive, they’ll be stressed all season and never catch up.”

Wait for warm soil

The right time to plant depends more on soil temperature than on the calendar. Across Oregon, cool-season vegetables such as peas, arugula, mustard, radish and turnip can usually be planted when soil reaches about 50°F. Gardeners can also sow carrots, beets, scallions, chives, parsley and other cutting greens, or set out transplants of kale, lettuce, chard, leeks and onions.

Warm-season crops — including tomatoes, peppers, cucumbers, corn and basil — need warmer soil.

“For warm-weather plants, the soil should be at least 60 degrees,” Miller said. “Ideally, tomatoes prefer 65 to 70.”

Soil temperature can vary depending on location and elevation. Gardeners along the coast or in Central and Eastern Oregon often need to wait a few weeks longer for soil to warm up compared with those in western valleys. An inexpensive soil thermometer is a simple tool to guide timing in any region.

Protect tender plants

If you can’t resist getting an early start on warm-season vegetables, Miller recommends protecting young plants from the chill with floating row covers, glass or plastic cloches, or even recycled milk jugs with the bottoms cut off.

For a larger setup, consult the Oregon State University Extension Service guide How to build your own raised bed cloche.

“Gardening depends on the weather — which is unpredictable — but it pays to wait,” Miller said.

For more region-specific guidance, including planting schedules for 45 vegetables, spacing recommendations and how much to grow for a family of four, visit the OSU Extension publication Growing your Own.

Weston Miller’s top tips for a successful vegetable garden

• Prepare the soil. Add ¼–1 inch of compost and a balanced fertilizer (equal numbers on the label) before planting. Work them 8–12 inches deep and rake smooth.
• For new beds: remove sod or weeds, then add 4–6 inches of compost, agricultural lime and fertilizer before mixing into the top 8–12 inches.
• Each fall, add 5–10 pounds of lime per 100 square feet.
• Feed transplants. Use a soluble fertilizer such as fish emulsion early in the season, especially if plants look sluggish.
• Use transplants when possible. Direct-seed only crops like carrots, parsnips, beets, radish, turnips, mustard and arugula. Most others grow best from transplants. Choose starts that are vigorous, not root-bound or pale.
• Stay ahead of weeds. Weed at least once a week for the first month to reduce competition and give vegetables a strong start.
• Watch for pests. Check plants often for slugs, aphids and cabbage butterfly larvae. Remove slugs by hand and drop them in soapy water. Squash insects found on the undersides of leaves.

Previously titled Let soil temperature guide you when planting vegetables