When to Plant Mizuna in San Diego County, CA
Your May gardening checklist
May is a pivotal month for San Diego County, California gardens. Focus on these tasks first and you'll set up the rest of the season for success.
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Start mizuna indoors
You're about 23 weeks out from your last frost — the perfect window to get these germinating indoors.
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It's harvest week for mizuna
Taste as you pick. The first ripe produce is the best feedback loop you'll get all season.
Get ahead of June
- First harvests: mizuna
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.
San Diego County, California is in USDA Zone 10b. The average last spring frost is April 16 and the first fall frost is November 1, giving you a growing season of approximately 199 days.
At an elevation of 2,613 feet, San Diego County receives approximately 18.2 inches of rainfall annually with predominantly loam soil. Summer highs average 92°F, providing good warmth for Mizuna during the growing season. With low rainfall, drip irrigation is essential for growing Mizuna successfully. Mulch heavily to conserve soil moisture.
San Diego County Soil Profile
Soil Type
Loam
Soil pH
5.7-7.5
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 San Diego County
How your county's soil matches Mizuna's growing requirements.
Soil pH
Your soil pH (5.7–7.5) overlaps with Mizuna's range (6.0–7.5), though not a perfect match.
Soil Texture
The loam soil in San Diego County is excellent for Mizuna — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.4%). Annual compost additions will help Mizuna.
How to Plant Mizuna
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
Succession Planting Mizuna
Sow every 3.4 weeks. Last sowing by Sep 17 to harvest before frost.
For a dedicated fall crop, sow by Sep 06.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Mizuna
Mizuna needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Mizuna Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 3" | 0" | ❄️ Dormant |
| Feb | — | 3.9" | 0" | ❄️ Dormant |
| Mar | — | 3.1" | 0" | ❄️ Dormant |
| Apr | 4.3" | 1.4" | 2.9" | 🚿 Regular watering |
| May | 4.3" | 0.5" | 3.8" | 🚿 Regular watering |
| Jun | 4.3" | 0.1" | 4.2" | 🚿 Regular watering |
| Jul | 4.3" | 0" | 4.3" | 🚿 Regular watering |
| Aug | 4.3" | 0" | 4.3" | 🚿 Regular watering |
| Sep | 4.3" | 0.2" | 4.1" | 🚿 Regular watering |
| Oct | 4.3" | 0.8" | 3.5" | 🚿 Regular watering |
| Nov | 4.3" | 1.8" | 2.5" | 🚿 Regular watering |
| Dec | — | 3.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Nov in San Diego County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Mizuna 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.
Mizuna Planting Timeline — San Diego County, CA
Mizuna Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 19 | Mar 19 – Apr 2 |
| Transplant Outdoors | April 16 | Apr 16 – Apr 30 |
| Direct Sow | March 26 | Mar 26 – Apr 16 |
| Harvest | May 21 | May 21 – Jun 18 |
| Fall Sowing | September 6 | Sep 6 – Sep 20 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors Direct Sow |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Harvest |
| June | Harvest |
| July | — |
| August | — |
| September | Fall Sowing |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1"/week · 2-3 times/week
📅 Days to Maturity
30–45 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 10b
📆 Growing Season
199 days in San Diego County
Growing Tips for Mizuna in San Diego County
Direct sow Mizuna outdoors after April 16 in San Diego County when soil has warmed and frost danger has passed.
Your generous 199.0-day season in San Diego County allows multiple plantings of Mizuna. Sow every 15.0 days for continuous harvest.
Common pests for Mizuna in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
San Diego County receives only 18" of rain annually. Mizuna needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
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
Check more plant combinations with our Companion Planting Checker →
Mizuna in Other Locations
Frequently Asked Questions
When should I plant Mizuna in San Diego County, CA?
San Diego County is in Zone 10b with an average last frost of April 16. Plan your Mizuna planting based on this frost date — see the calendar above for exact timing.
What planting zone is San Diego County, CA?
San Diego County, California is in USDA Hardiness Zone 10b. The average last spring frost is April 16 and first fall frost is November 1.
Your San Diego County Garden Planner — Free
A 24-page printable planner built for San Diego County (Zone 10b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.