When To Plant Vegetables In Seattle

Knowing when to plant vegetables in Seattle is the key to a successful garden in our unique climate. Our cool, wet springs and mild, dry summers create a specific rhythm that your planting schedule must follow. Get it right, and you’ll enjoy a long, bountiful harvest. Get it wrong, and you might be watching your tomatoes struggle in the June gloom. This guide will walk you through Seattle’s ideal planting schedule, month by month.

First, forget the last frost date you read about for other regions. Seattle’s maritime influence means our weather is its own beast. While the average last spring frost is around March 15th, it can vary. A more reliable guide is soil temperature. Many seeds simply won’t germinate in cold, soggy soil, no matter how sunny the day seems.

This annual calendar is your blueprint. Think of it in two main seasons: the cool-season rush from late winter through spring, and the warm-season planting after the danger of frost has truly passed and soils have warmed.

Understanding Your Seattle Microclimate

Seattle isn’t just one garden zone. Your specific location makes a huge difference. Gardens near the water (Ballard, West Seattle) benefit from milder temps but more summer fog. Inland areas (Lake City, Beacon Hill) heat up faster. The “convergence zone” north of the city can get more dramatic weather. Observe your own yard’s sun exposure and wind patterns.

Essential Tools for Timing

A simple soil thermometer. Plant when the soil is ready, not just when the calendar says.
A rain gauge to track precipitation and avoid over-watering.
Season extenders like cloches, row covers, or cold frames. These are invaluable for getting a head start.

Late Winter to Early Spring (February – March)

This is the time for hardy, cool-season crops. The work begins indoors and in prepared garden beds.

Indoors (Start Seeds): Onions, leeks, celery, and early brassicas like broccoli and cabbage can be started indoors in February. By March, add kale, lettuce, and chard to your seed trays.
Outdoors (Direct Sow or Transplant): As soon as soil is workable—not muddy—you can plant peas, spinach, and radishes. Towards late March, if the soil is warming, try direct sowing carrots, beets, and parsnips. You can also plant out started seedlings of kale and collards.

Mid to Late Spring (April – May)

The garden explodes with activity now. Risk of frost diminishes significantly by mid-May.

Indoors (Start Seeds): This is prime time for warm-season crops. Start tomatoes, peppers, eggplant, and basil indoors in early April. They need a long, warm head start.
Outdoors (Direct Sow or Transplant): Direct sow beans, corn, and squash in late May. Transplant your hardened-off broccoli, cabbage, and lettuce seedlings. Continue successions of radishes and lettuces for continous harvest.

Early Summer (June)

June can be surprisingly cool in Seattle—our famous “June Gloom.” Don’t rush heat-lovers if the soil is still cold.

Outdoors (Transplant): The first week of June is generally safe to transplant tomatoes, peppers, cucumbers, and basil into the garden. Ensure soil is warm to the touch.
Outdoors (Direct Sow): You can make final direct sowings of beans, carrots, and beets for fall harvest. Its also a good time to plant winter squash.

Summer to Fall (July – September)

This is for fall and winter harvests. Many gardeners miss this second planting season.

In July, direct sow fast-growing crops like bush beans, lettuce, and radishes.
In mid-July, start your fall brassicas: broccoli, cauliflower, and kale. Start them in a shaded nursery bed or indoors to escape the peak heat.
By August, sow spinach, Swiss chard, and overwintering onions. These will establish before winter.
September is for planting garlic cloves, which will root in fall and be ready for harvest next summer.

Vegetable-Specific Planting Tips

Some crops need special attention in our climate.

Tomatoes & Peppers

Choose varieties with shorter “days to maturity” (under 75 days is safe). Always start indoors. Use black plastic or red mulch to warm the soil before planting. A sunny, south-facing wall provides extra heat.

Leafy Greens (Lettuce, Kale, Spinach)

You can grow these almost year-round with protection. Succession plant every 2-3 weeks for a constant supply. Provide afternoon shade in mid-summer to prevent bolting.

Root Vegetables (Carrots, Beets)

Loose, rock-free soil is critical. Direct sow only; they don’t transplant well. Thin seedlings ruthlessly to give roots room to size up. Keep soil consistently moist for even growth.

Common Mistakes to Avoid

Planting too early: Impatience is a garden’s biggest enemy. Cold soil stunts growth.
Ignoring soil prep: Seattle soil often needs compost for drainage and fertility. Don’t skip this step.
Crowding plants: Follow spacing on seed packets. Good air flow prevents fungal diseases in our damp climate.
Forgetting to harden off: Never move seedlings straight from indoors to the garden. Acclimate them to outdoor conditions over 7-10 days.

FAQ: Seattle Vegetable Planting

What is the best month to start a garden in Seattle?
You can start in February by sowing some seeds indoors and planting peas outdoors. The main planting months are March through June.

When should I plant tomatoes in Seattle?
Start tomato seeds indoors in early April. Transplant seedlings into the garden in early to mid-June, after the soil has thoroughly warmed.

Can you grow vegetables year-round in Seattle?
Yes, with protection like cold frames or cloches. Hardy crops like kale, spinach, and some lettuces can survive our winters and provide harvests.

What vegetables grow easiest in Seattle?
Cool-season crops thrive: peas, lettuce, kale, chard, radishes, and broccoli are very reliable. For beginners, these are your best bet.

How do I protect my garden from Seattle’s spring rain?
Raised beds improve drainage immensely. Use row covers to shield young plants from heavy downpours and prevent soil compaction.

Following Seattle’s natural planting rhythm takes the guesswork out of gardening. By syncing your schedule with the soil’s temperature and our specific seasons, you give every seed and seedling the best possible start. Keep a simple garden journal each year, noting what worked and when. Over time, you’ll develop an intuitive sense for the perfect moment to get each plant into the ground, ensuring a productive and rewarding garden season after season.