When to Plant Sweet Potatoes in Mendocino County, CA
May in the garden — Mendocino County, California
May is a pivotal month for Mendocino County, California gardens. Focus on these tasks first and you'll set up the rest of the season for success.
-
Time to start sweet potatoes inside
Label every cell. You will absolutely forget which is which otherwise.
June prep starts now
- First harvests: sweet potatoes
Sweet potatoes are a warm-season root crop that produces nutritious, sweet tubers in orange, white, and purple varieties. They need a long, hot growing season.
Mendocino County, California is in USDA Zone 9b. The average last spring frost is March 23 and the first fall frost is November 9, giving you a growing season of approximately 231 days.
At an elevation of 180 feet, Mendocino County receives approximately 24 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 87°F, providing good warmth for Sweet Potatoes during the growing season. Sandy soil warms quickly in spring — great for early planting — but Sweet Potatoes will need more frequent watering and organic matter to retain nutrients.
Mendocino County Soil Profile
Soil Type
Sandy Loam
Soil pH
6.1-7.2
Drainage
Well Drained
Monthly Watering Guide for Sweet Potatoes
Sweet Potatoes needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Sweet Potatoes Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 5.2" | 0" | ❄️ Dormant |
| Feb | — | 4.6" | 0" | ❄️ Dormant |
| Mar | 4.3" | 3.7" | 0.6" | 💧 Light watering |
| Apr | 4.3" | 1.9" | 2.4" | 🚿 Regular watering |
| May | 4.3" | 0.6" | 3.7" | 🚿 Regular watering |
| Jun | 4.3" | 0.2" | 4.1" | 🚿 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" | 1" | 3.3" | 🚿 Regular watering |
| Nov | 4.3" | 2.6" | 1.7" | 💧 Light watering |
| Dec | — | 3.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Mendocino County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Sweet Potatoes Planting Timeline — Mendocino County, CA
Sweet Potatoes Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 9 | Feb 9 – Feb 23 |
| Transplant Outdoors | March 30 | Mar 30 – Apr 13 |
| Direct Sow | March 23 | Mar 23 – Apr 13 |
| Harvest | June 29 | Jun 29 – Aug 17 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Transplant Outdoors Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 5.5–6.5 · Your soil: N/A
🗺️ USDA Zone
Zone 9b
📆 Growing Season
231 days in Mendocino County
Growing Tips for Mendocino County
Plant slips (rooted sprouts) after soil is thoroughly warm. Build raised mounds for better root development. Cure harvested roots at 80-85F for 10 days to develop sweetness.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Sweet Potatoes in Other Locations
Frequently Asked Questions
When should I plant Sweet Potatoes in Mendocino County, CA?
Mendocino County is in Zone 9b with an average last frost of March 23. Plan your Sweet Potatoes planting based on this frost date — see the calendar above for exact timing.
What planting zone is Mendocino County, CA?
Mendocino County, California is in USDA Hardiness Zone 9b. The average last spring frost is March 23 and first fall frost is November 9.
Your Mendocino County Garden Planner — Free
A 24-page printable planner built for Mendocino 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.