When to Plant Mizuna in King County, WA
Mizuna is a mild-flavored Japanese mustard green with feathery, deeply serrated leaves. It is fast-growing and makes an excellent addition to salads and stir-fries.
King County, Washington is in USDA Zone 8b. The average last spring frost is April 7 and the first fall frost is October 30, giving you a growing season of approximately 206 days.
At an elevation of 258 feet, King County receives approximately 37.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 89°F, providing good warmth for Mizuna during the growing season.
King County Soil Profile
Soil Type
Silt Loam
Soil pH
5.7-6.4
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.
Plant Water Budget
Mizuna Planting Timeline — King County, WA
Mizuna Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 3 | Mar 3 – Mar 17 |
| Transplant Outdoors | April 7 | Apr 7 – Apr 21 |
| Direct Sow | March 24 | Mar 24 – Apr 14 |
| Fall Sowing | August 21 | Aug 21 – Sep 4 |
| Harvest | May 12 | May 12 – Jun 9 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | Harvest |
| June | Harvest |
| July | — |
| August | Fall Sowing |
| September | Fall Sowing |
| October | — |
| November | — |
| December | — |
Growing Conditions
Sun
Partial Shade (3-6 hours)
Water
Moderate — regular watering
Days to Maturity
30–45 days
Soil pH
6 – 7.5
USDA Zone
Zone 8b
Growing Season
206 days
Growing Tips for King County
Direct sow in spring or fall. Harvest outer leaves as needed for a cut-and-come-again approach. Mizuna is one of the most cold-tolerant Asian greens.
Companion Planting
Good Companions
Avoid Planting Near
Level Up Your Garden
Mizuna in Other Locations
Frequently Asked Questions
When should I plant Mizuna in King County, WA?
King County is in Zone 8b with an average last frost of April 7. Plan your Mizuna planting based on this frost date — see the calendar above for exact timing.
What planting zone is King County, WA?
King County, Washington is in USDA Hardiness Zone 8b. The average last spring frost is April 7 and first fall frost is October 30.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help King County gardeners in Zone 8b organize planting dates, track what's growing, and never miss a planting window.
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