Spring Planting Guide
If you’re gardening in Zone 8b, spring is the make-or-break season. The window between our last frost (around April 15th in South King County) and the intense heat of summer is relatively short, but it’s when we can grow some of the most productive crops of the year. The key is understanding what to plant when—and that’s more nuanced than just “wait until it’s warm.”
Here’s what I’ve learned from working with dozens of gardens across Kent and the surrounding area: the gardeners who succeed in spring aren’t the ones planting everything at once. They’re the ones staggering their plantings, starting some indoors, direct-seeding others, and timing everything around frost dates and soil temperature.
March: The Planning and Starting Phase
March is deceptive in Zone 8b. Yes, we might have sunny, warm-looking days. But the soil is still cold—usually in the mid-40s to low 50s—and frost is absolutely still a threat until mid-April. This is not a month to plant tender vegetables outdoors.
What to do instead:
Start seeds indoors: This is the time to start tomatoes, peppers, and eggplants under lights. These crops need 6–8 weeks of growth before they’re ready to transplant outdoors (which won’t be until late May). Start them now and you’ll have strong, healthy transplants ready to go.
Direct-sow cold-hardy crops: Peas, spinach, lettuce, kale, and chard don’t mind the cold. In fact, they prefer it. If your beds are dry enough to work with (not muddy), you can plant these directly into the ground in late March. They’ll germinate slowly—expect 2–3 weeks—but they’ll establish strong roots before the heat arrives.
Prepare your beds: If you haven’t already refreshed your beds with compost, do it now. Work in 1–2 inches of good compost or composted manure. The soil microbes are just waking up; give them some food to work with.
April: The Transition Month
April is when things start moving. Your direct-seeded crops from March are sprouting. The days are noticeably longer. But frost is still possible—watch the forecast carefully.
Succession plant cold crops: Make a second planting of peas, spinach, lettuce, and chard around April 1st. Stagger plantings every 2–3 weeks until mid-May. This extends your harvest across the entire spring instead of everything maturing at once.
Start warm-season crops outdoors: Around April 15th (or after the last frost date in your specific microclimate), you can begin hardening off your indoor seedlings and planting warm-season crops directly if you’re willing to take a small frost risk. Beans, squash, and cucumber can go in. But be honest with yourself: if an unexpected frost comes, those plants will die. Some gardeners wait until May to be safe. Both approaches work.
Watch the soil temperature: For root crops like carrots, beets, and radishes, soil temperature matters more than air temperature. Wait until the soil reaches at least 50°F (ideally 60°F) before planting. If you don’t have a soil thermometer, a good rule of thumb in Zone 8b is mid-April.
May: Full Steam Ahead
By May, frost risk is essentially zero. This is when you plant everything that needs warmth: tomatoes, peppers, eggplants, basil, beans, squash, cucumber, and melons. If you’ve been holding back waiting for safety, this is the month to commit.
Transplant indoor starts: Your tomato and pepper seedlings should be sturdy by now. Harden them off (gradually expose them to outdoor conditions over 7–10 days) and plant them into the garden. Space tomatoes 24–36 inches apart; peppers 18–24 inches apart. Plant deep—tomatoes can be planted up to their first true leaves, and they’ll root along the buried stem for extra strength.
Continue succession planting: Make one final planting of beans, squash, and cucumbers around May 1st if you haven’t already. By mid-May, summer heat is on the horizon, and some of these crops will start struggling if planted too late.
Plant heat-lovers: Basil, melons, and okra (if you’re adventurous) thrive in May-planted gardens. By the time summer heat arrives in July, they’ll be established and productive.
What to Plant in Spring: The 8B Crop Rundown
| Crop | March | April | May | Notes |
|---|---|---|---|---|
| Peas | Direct-sow | Direct-sow (early month) | Too late; heat kills them | Succession plant every 2 weeks in March–April |
| Spinach / Lettuce | Direct-sow | Direct-sow | Direct-sow (early only) | Stagger plantings; switches to fall crop in summer |
| Kale / Chard | Start indoors or direct-sow | Transplant or direct-sow | Transplant only | Extremely cold-hardy; tolerates summer but prefers cool seasons |
| Tomatoes | Start indoors | Harden off | Transplant to garden | Plant deep; tie up early for support |
| Peppers | Start indoors | Harden off | Transplant to garden | Slower to start than tomatoes; worth the wait |
| Beans | — | Direct-sow (late month) | Direct-sow | Plant 1 inch deep; space 4–6 inches apart |
| Squash / Zucchini | — | Start indoors (optional) | Direct-sow or transplant | Direct-sow mid-May; space 24–36 inches apart |
| Cucumber | — | Start indoors (optional) | Direct-sow or transplant | Warm soil lover; wait until May |
| Carrot / Beets | — | Direct-sow | Direct-sow | Direct-sow in bands; thin seedlings at 2 inches |
| Basil | — | — | Direct-sow or transplant | Plant after May 1st; thrives in heat |
The Biggest Spring Mistakes I See
Planting too early. I watch gardeners put tomatoes and peppers in the ground in late March because they see a warm day. One frost and they’re gone. Wait until late May. I promise your garden will catch up.
Forgetting to succession plant. If you plant all your lettuce at once, you’ll have an overwhelming harvest for two weeks, then nothing. Plant small amounts every 2–3 weeks and you’ll harvest continuously.
Planting in cold, wet soil. Seed rot is real. If the soil is still muddy and cool, wait a week. Germination rates are so much higher in warm, well-drained soil.
Ignoring frost dates. Know your frost date. In South King County, it’s approximately April 15th, but microclimates vary. If you’re in a low-lying area that gets frost later, account for that. If you’re on a slope with good drainage, you might be safe earlier. Pay attention to your specific yard.
Your Spring Success Strategy
The spring that works is the one where you start some seeds indoors, plant cold crops outdoors ASAP, stagger your plantings so you’re not harvesting everything at once, and resist the temptation to plant warm-season crops too early. It takes patience, but by mid-June, you’ll be harvesting lettuce, peas, and spinach while your tomatoes and peppers are flowering—exactly what you want.
If you’re not sure which crops will thrive in your specific yard, or you want help timing your plantings for maximum productivity, let’s talk. I can assess your sun exposure, frost risk, and soil conditions, then design a planting calendar that actually works for your space and your goals. Or explore our garden packages to see what a full setup looks like.