When to Plant Chard in Sonoma County, CA
What to do in May
Your garden in Sonoma County, California is working on a schedule, even when you're not. Here's where you should be this May.
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Start harvesting chard
If you can't use it all right away, check the food-preservation section of your planner.
To set up a strong June, finish these tasks
- First harvests: chard
Swiss chard is a colorful, heat-tolerant green with large crinkled leaves and vibrant stalks in red, yellow, and white. Both the leaves and stems are edible and nutritious.
Sonoma County, California is in USDA Zone 9b. The average last spring frost is February 26 and the first fall frost is November 26, giving you a growing season of approximately 273 days.
At an elevation of 91 feet, Sonoma County receives approximately 31.1 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 90°F, providing good warmth for Chard during the growing season. Sandy soil warms quickly in spring — great for early planting — but Chard will need more frequent watering and organic matter to retain nutrients.
Sonoma County Soil Profile
Soil Type
Sandy Loam
Soil pH
5.9-7
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 Sonoma County
How your county's soil matches Chard's growing requirements.
Soil pH
Your soil pH (5.9–7.0) overlaps with Chard's range (6.0–7.0), though not a perfect match.
Soil Texture
Sandy soil in Sonoma County warms quickly in spring but drains fast. Chard will need more frequent watering and regular compost additions to retain nutrients.
Drainage
Drainage is adequate for Chard.
Organic Matter
Organic matter is moderate (2.5%). Annual compost additions will help Chard.
How to Plant Chard
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
Succession Planting Chard
Sow every 5.7 weeks. Last sowing by Sep 27 to harvest before frost.
For a dedicated fall crop, sow by Oct 01.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Chard
Chard needs approximately 0.8 inches of water per week (3.5" per month). Here's how your county's rainfall compares month by month.
| Month | Chard Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 6.2" | 0" | ❄️ Dormant |
| Feb | 3.5" | 6.8" | 0" | ✅ Rainfall sufficient |
| Mar | 3.5" | 5.2" | 0" | ✅ Rainfall sufficient |
| Apr | 3.5" | 2.3" | 1.2" | 💧 Light watering |
| May | 3.5" | 0.8" | 2.7" | 🚿 Regular watering |
| Jun | 3.5" | 0.1" | 3.4" | 🚿 Regular watering |
| Jul | 3.5" | 0" | 3.5" | 🚿 Regular watering |
| Aug | 3.5" | 0" | 3.5" | 🚿 Regular watering |
| Sep | 3.5" | 0.4" | 3.1" | 🚿 Regular watering |
| Oct | 3.5" | 1.3" | 2.2" | 🚿 Regular watering |
| Nov | 3.5" | 2.7" | 0.8" | 💧 Light watering |
| Dec | — | 5.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Feb–Nov in Sonoma County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Chard 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.
Chard Planting Timeline — Sonoma County, CA
Chard Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 29 | Jan 29 – Feb 12 |
| Transplant Outdoors | February 26 | Feb 26 – Mar 12 |
| Direct Sow | February 5 | Feb 5 – Feb 26 |
| Harvest | April 23 | Apr 23 – Jun 11 |
| Fall Sowing | October 1 | Oct 1 – Oct 15 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors |
| February | Start Indoors Transplant Outdoors Direct Sow |
| March | Transplant Outdoors |
| April | Harvest |
| May | Harvest |
| June | Harvest |
| July | — |
| August | — |
| September | — |
| October | Fall Sowing |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
0.8"/week · 1-2 times/week
📅 Days to Maturity
50–60 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 9b
📆 Growing Season
273 days in Sonoma County
Growing Tips for Chard in Sonoma County
Direct sow Chard outdoors after February 26 in Sonoma County when soil has warmed and frost danger has passed.
Sandy soil in Sonoma County dries quickly — mulch Chard with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
General growing tips
Direct sow or transplant after last frost. Harvest outer leaves regularly to encourage continuous production. Chard tolerates both heat and light frost.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Chard in Other Locations
Frequently Asked Questions
When should I plant Chard in Sonoma County, CA?
Sonoma County is in Zone 9b with an average last frost of February 26. Plan your Chard planting based on this frost date — see the calendar above for exact timing.
What planting zone is Sonoma County, CA?
Sonoma County, California is in USDA Hardiness Zone 9b. The average last spring frost is February 26 and first fall frost is November 26.
Your Sonoma County Garden Planner — Free
A 24-page printable planner built for Sonoma 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.