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When to Plant Mustard Greens in Solano County, CA

Solano County, California Zone 9b May

Your May game plan for Solano County, California

A quick May briefing for Solano County, California gardeners — what's urgent, what's next, and what can wait.

Avg. last frost February 9
Avg. first frost December 3
Soil temp (4") 76°F
Watering Critical
Pest pressure High
Daylight 14.1 hrs
  1. Bring in the mustard greens

    This is the payoff month. Bring a basket, bring a friend, and get into the beds.

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Mustard greens are fast-growing brassicas with a spicy, peppery kick. They come in green, red, and purple varieties and are excellent cooked or in salads.

Solano County, California is in USDA Zone 9b. The average last spring frost is February 9 and the first fall frost is December 3, giving you a growing season of approximately 297 days.

At an elevation of 376 feet, Solano County receives approximately 40.4 inches of rainfall annually with predominantly loam soil. Summer highs average 95°F, so Mustard Greens may need afternoon shade and extra watering during peak heat.

Solano County, CA (Zone 9b) Year-round
297 days
Last Spring Frost February 9
297 growing days
First Fall Frost December 3

Solano County Soil Profile

Soil Type

Loam

Soil pH

6.8-7.3

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (207 days to spare)
Start indoors: Dec 28 Transplant: Jan 25 🍅 Harvest: Mar 1 – May 3
Recommended (50%) ✓ Fits season (199 days to spare)
Start indoors: Jan 12 Transplant: Feb 9 🍅 Harvest: Mar 16 – May 18
Safe Start (90%) ✓ Fits season (183 days to spare)
Start indoors: Feb 13 Transplant: Mar 13 🍅 Harvest: Apr 17 – Jun 19

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 Solano County

How your county's soil matches Mustard Greens's growing requirements.

Soil pH

Your soil pH (6.8–7.3) is more alkaline than Mustard Greens prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

The loam soil in Solano County is excellent for Mustard Greens — good drainage, moisture retention, and nutrient holding capacity.

Drainage

Drainage is adequate for Mustard Greens.

Organic Matter

Organic matter is moderate (2.6%). Annual compost additions will help Mustard Greens.

How to Plant Mustard Greens

0.5"
Planting Depth
6"
Between Plants
12"
Between Rows

Fall planting: Sow 8 weeks before your first frost date for a fall harvest.

Succession Planting Mustard Greens

12
successive plantings in your 297-day season

Sow every 3.4 weeks. Last sowing by Oct 14 to harvest before frost.

For a dedicated fall crop, sow by Oct 08.

Plant Water Budget

Plant needs
0.7″/week
Rainfall provides
0.6″/week
You supply
0.4″/week
Watering frequency 1-2 times/week
Season total 1,084 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Mustard Greens

Mustard Greens needs approximately 0.7 inches of water per week (3" per month). Here's how your county's rainfall compares month by month.

Month Mustard Greens Needs Rainfall You Supplement Action
Jan 8.9" 0" ❄️ Dormant
Feb 3" 8.4" 0" ✅ Rainfall sufficient
Mar 3" 6.6" 0" ✅ Rainfall sufficient
Apr 3" 2.7" 0.3" 💧 Light watering
May 3" 1" 2" 🚿 Regular watering
Jun 3" 0.2" 2.8" 🚿 Regular watering
Jul 3" 0" 3" 🚿 Regular watering
Aug 3" 0" 3" 🚿 Regular watering
Sep 3" 0.4" 2.6" 🚿 Regular watering
Oct 3" 1.9" 1.1" 💧 Light watering
Nov 3" 3.3" 0" ✅ Rainfall sufficient
Dec 3" 7.1" 0" ✅ Rainfall sufficient

Water needs are for active growing months only (Feb–Dec in Solano County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Mustard Greens 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.

Mustard Greens needs ~850 GDD — county provides 6,332 GDD Excellent fit

Mustard Greens Planting Timeline — Solano County, CA

Mustard Greens Planting Calendar

Activity When Date Range
Start Indoors January 12 Jan 12 – Jan 26
Transplant Outdoors February 9 Feb 9 – Feb 23
Direct Sow January 19 Jan 19 – Feb 9
Harvest March 16 Mar 16 – May 18
Fall Sowing October 8 Oct 8 – Oct 22

Plant 0.5" deep · 6" apart · Rows 12" apart

Month-by-Month Timeline

MonthActivities
January Start Indoors Direct Sow
February Transplant Outdoors Direct Sow
March Harvest
April Harvest
May Harvest
June
July
August
September
October Fall Sowing
November
December

Growing Conditions

☀️ Sun

Partial Shade (3-6 hours)

💧 Water

0.7"/week · 1-2 times/week

📅 Days to Maturity

30–50 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 9b

📆 Growing Season

297 days in Solano County

Growing Tips for Mustard Greens in Solano County

Direct sow Mustard Greens outdoors after February 09 in Solano County when soil has warmed and frost danger has passed.

Your generous 298.0-day season in Solano County allows multiple plantings of Mustard Greens. Sow every 15.0 days for continuous harvest.

Common pests for Mustard Greens in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.

General growing tips

Direct sow in early spring or fall. Harvest young leaves for milder flavor. Plants bolt quickly in heat so grow as a cool-season crop or provide shade.

Companion Planting

Good Companions

Avoid Planting Near

  • Strawberries

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Mustard Greens in Solano County, CA?

Solano County is in Zone 9b with an average last frost of February 9. Plan your Mustard Greens planting based on this frost date — see the calendar above for exact timing.

What planting zone is Solano County, CA?

Solano County, California is in USDA Hardiness Zone 9b. The average last spring frost is February 9 and first fall frost is December 3.

🌱

Your Solano County Garden Planner — Free

A 24-page printable planner built for Solano County (Zone 9b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Solano County, CA. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.