When to Plant Parsley in San Mateo County, CA
May to-do list for San Mateo County, California
Your garden in San Mateo County, California is working on a schedule, even when you're not. Here's where you should be this May.
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Harvest parsley as they ripen
Don't tug. Use scissors or pruners for clean cuts — torn stems invite disease.
Parsley is a biennial herb available in flat-leaf (Italian) and curly varieties. It is a nutritional powerhouse rich in vitamins C and K and adds fresh flavor to countless dishes.
San Mateo County, California is in USDA Zone 10a. The average last spring frost is January 18 and the first fall frost is December 12, giving you a growing season of approximately 328 days.
At an elevation of 277 feet, San Mateo County receives approximately 16.9 inches of rainfall annually with predominantly loam soil. Summer highs average 81°F, so choose short-season varieties of Parsley to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Parsley successfully. Mulch heavily to conserve soil moisture.
San Mateo County Soil Profile
Soil Type
Loam
Soil pH
6.8-7.2
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 Mateo County
How your county's soil matches Parsley's growing requirements.
Soil pH
Your soil pH (6.8–7.2) overlaps with Parsley's range (6.0–7.0), though not a perfect match.
Soil Texture
The loam soil in San Mateo County is excellent for Parsley — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Parsley.
Organic Matter
Organic matter is moderate (2.6%). Annual compost additions will help Parsley.
How to Plant Parsley
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
Succession Planting Parsley
Sow every 6.9 weeks. Last sowing by Sep 23 to harvest before frost.
For a dedicated fall crop, sow by Oct 17.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Parsley
Parsley 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 | Parsley Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | 2.6" | 3.9" | 0" | ✅ Rainfall sufficient |
| Feb | 2.6" | 3.4" | 0" | ✅ Rainfall sufficient |
| Mar | 2.6" | 2.7" | 0" | ✅ Rainfall sufficient |
| Apr | 2.6" | 1.2" | 1.4" | 🚿 Regular watering |
| May | 2.6" | 0.4" | 2.2" | 🚿 Regular watering |
| Jun | 2.6" | 0.1" | 2.5" | 🚿 Regular watering |
| Jul | 2.6" | 0" | 2.6" | 🚿 Regular watering |
| Aug | 2.6" | 0" | 2.6" | 🚿 Regular watering |
| Sep | 2.6" | 0.2" | 2.4" | 🚿 Regular watering |
| Oct | 2.6" | 0.7" | 1.9" | 🚿 Regular watering |
| Nov | 2.6" | 1.4" | 1.2" | 💧 Light watering |
| Dec | 2.6" | 2.9" | 0" | ✅ Rainfall sufficient |
Water needs are for active growing months only (Jan–Dec in San Mateo County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Parsley 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.
Parsley Planting Timeline — San Mateo County, CA
Parsley Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | December 21 | Dec 21 – Jan 4 |
| Transplant Outdoors | January 11 | Jan 11 – Jan 25 |
| Direct Sow | December 28 | Dec 28 – Jan 18 |
| Harvest | March 15 | Mar 15 – May 17 |
| Fall Sowing | October 17 | Oct 17 – Oct 31 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Transplant Outdoors Direct Sow |
| February | — |
| March | Harvest |
| April | Harvest |
| May | Harvest |
| June | — |
| July | — |
| August | — |
| September | — |
| October | Fall Sowing |
| November | — |
| December | Start Indoors Direct Sow |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
0.6"/week · 1-2 times/week
📅 Days to Maturity
60–80 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 10a
📆 Growing Season
328 days in San Mateo County
Growing Tips for Parsley in San Mateo County
Direct sow Parsley outdoors after January 18 in San Mateo County when soil has warmed and frost danger has passed.
Common pests for Parsley in this region include carrot rust fly and parsleyworm. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 6-8 weeks before last frost. Soak seeds overnight as germination is slow. Harvest outer stems first to keep plants productive. Parsley attracts swallowtail butterflies.
Companion Planting
Good Companions
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Check more plant combinations with our Companion Planting Checker →
Parsley in Other Locations
Frequently Asked Questions
When should I plant Parsley in San Mateo County, CA?
San Mateo County is in Zone 10a with an average last frost of January 18. Plan your Parsley planting based on this frost date — see the calendar above for exact timing.
What planting zone is San Mateo County, CA?
San Mateo County, California is in USDA Hardiness Zone 10a. The average last spring frost is January 18 and first fall frost is December 12.
Your San Mateo County Garden Planner — Free
A 24-page printable planner built for San Mateo County (Zone 10a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.