When to Plant Basil in Snohomish County, WA
May to-do list for Snohomish County, Washington
May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Snohomish County, Washington.
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Fire up the seed-starting tray: basil
Give them 6–8 weeks indoors before the last frost and you'll transplant into warm soil with seedlings that are already leaping.
Looking ahead to June
- First harvests: basil
Basil is a fragrant warm-season herb essential to Italian and Thai cuisines. It comes in many varieties including sweet, Thai, purple, and lemon types.
Snohomish County, Washington is in USDA Zone 8b. The average last spring frost is March 25 and the first fall frost is November 2, giving you a growing season of approximately 222 days.
At an elevation of 230 feet, Snohomish County receives approximately 50.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 90°F, providing good warmth for Basil during the growing season. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Basil root diseases.
Snohomish County Soil Profile
Soil Type
Silt Loam
Soil pH
5.7-6.8
Drainage
Well Drained
Plant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Soil Compatibility in Snohomish County
How your county's soil matches Basil's growing requirements.
Soil pH
Your soil pH (5.7–6.8) overlaps with Basil's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Snohomish County is excellent for Basil — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (5.4%) — Basil will thrive.
How to Plant Basil
Succession Planting Basil
Sow every 5.7 weeks. Last sowing by Aug 19 to harvest before frost.
Plant Water Budget
Monthly Watering Guide for Basil
Basil needs approximately 0.6 inches of water per week (2.6" per month). Here's how your county's rainfall compares month by month.
| Month | Basil Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 7.7" | 0" | ❄️ Dormant |
| Feb | — | 5.6" | 0" | ❄️ Dormant |
| Mar | 2.6" | 5" | 0" | ✅ Rainfall sufficient |
| Apr | 2.6" | 3.6" | 0" | ✅ Rainfall sufficient |
| May | 2.6" | 2.6" | 0" | ✅ Rainfall sufficient |
| Jun | 2.6" | 1.6" | 1" | 💧 Light watering |
| Jul | 2.6" | 0.7" | 1.9" | 🚿 Regular watering |
| Aug | 2.6" | 1" | 1.6" | 🚿 Regular watering |
| Sep | 2.6" | 2" | 0.6" | 💧 Light watering |
| Oct | 2.6" | 4.2" | 0" | ✅ Rainfall sufficient |
| Nov | 2.6" | 8" | 0" | ✅ Rainfall sufficient |
| Dec | — | 8.5" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Snohomish County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Basil Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Basil Planting Timeline — Snohomish County, WA
Basil Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 4 | Feb 4 – Feb 18 |
| Transplant Outdoors | April 8 | Apr 8 – Apr 22 |
| Direct Sow | April 1 | Apr 1 – Apr 22 |
| Harvest | June 3 | Jun 3 – Aug 5 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | — |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.6"/week · Natural rainfall sufficient
📅 Days to Maturity
50–75 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 8b
📆 Growing Season
222 days in Snohomish County
Growing Tips for Basil in Snohomish County
Direct sow Basil outdoors after March 25 in Snohomish County when soil has warmed and frost danger has passed.
General growing tips
Start seeds indoors or direct sow after last frost. Pinch flower buds to extend leaf production. Harvest leaves from the top down, cutting just above a leaf pair.
Recommended Basil Varieties for Snohomish County
Downy mildew-resistant basil for your humid climate
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Isolate 150 ft between varieties. Different basil species can cross.
Basil in Other Locations
Frequently Asked Questions
When should I plant Basil in Snohomish County, WA?
Snohomish County is in Zone 8b with an average last frost of March 25. Plan your Basil planting based on this frost date — see the calendar above for exact timing.
What planting zone is Snohomish County, WA?
Snohomish County, Washington is in USDA Hardiness Zone 8b. The average last spring frost is March 25 and first fall frost is November 2.
Your Snohomish County Garden Planner — Free
A 24-page printable planner built for Snohomish County (Zone 8b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.