When to plant Geraniums in Sonoma County, CA
Sonoma County's short 274-day growing season means one Geraniums planting between January 29 and February 12. No fall crop in Zone 9b.
When to Plant Geraniums in Sonoma County, CA
This month in Sonoma County, California
If you only do a handful of things in the garden this July, make it these. They're sequenced around your zone's frost timing.
-
Pick geraniums
If you can't use it all right away, check the food-preservation section of your planner.
To set up a strong August, finish these tasks
- First harvests: geraniums
Geraniums (Pelargonium × hortorum) are tender perennials grown as warm-season annuals throughout North America. Prized for their bold flower clusters, long bloom period, and tolerance of summer heat when planted in well-drained soil, they anchor window boxes, containers, and bed borders from late spring until hard frost. Zones 9b–11b can overwinter plants in the ground.
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 Geraniums during the growing season. Sandy soil warms quickly in spring — great for early planting — but Geraniums 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
Geraniums 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 Geraniums's growing requirements.
Soil pH
Your soil pH (5.9–7.0) overlaps with Geraniums'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. Geraniums will need more frequent watering and regular compost additions to retain nutrients.
Drainage
Drainage is adequate for Geraniums.
Organic Matter
Organic matter is moderate (2.5%). Annual compost additions will help Geraniums.
How to Plant Geraniums
Succession Planting Geraniums
Sow every 8 weeks. Last sowing by Aug 18 to harvest before frost.
Geraniums Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Geraniums
Geraniums needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Geraniums Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 6.2" | 0" | ❄️ Dormant |
| Feb | 4.3" | 6.8" | 0" | ✅ Rainfall sufficient |
| Mar | 4.3" | 5.2" | 0" | ✅ Rainfall sufficient |
| Apr | 4.3" | 2.3" | 2" | 💧 Light watering |
| May | 4.3" | 0.8" | 3.5" | 🚿 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" | 0.4" | 3.9" | 🚿 Regular watering |
| Oct | 4.3" | 1.3" | 3" | 🚿 Regular watering |
| Nov | 4.3" | 2.7" | 1.6" | 💧 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.
Geraniums 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.
Geraniums Planting Timeline — Sonoma County, CA
Geraniums Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | December 18 | Dec 18 – Jan 1 |
| Transplant Outdoors | January 29 | Jan 29 – Feb 12 |
| Bloom | April 9 | Apr 9 – Oct 22 |
Plant 0.1" deep · 12" apart · Rows 14" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Transplant Outdoors |
| February | Transplant Outdoors |
| March | — |
| April | Bloom |
| May | Bloom |
| June | Bloom |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | Start Indoors |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · 2-3 times/week
📅 Days to Maturity
70–100 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 9b
📆 Growing Season
273 days in Sonoma County
Growing Tips for Geraniums in Sonoma County
Direct sow Geraniums outdoors after February 26 in Sonoma County when soil has warmed and frost danger has passed.
Sandy soil in Sonoma County dries quickly — mulch Geraniums with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
General growing tips
Start seeds indoors 10–12 weeks before last frost — germination is slow and erratic without bottom heat (70–75°F). Transplant after frost danger passes. Geraniums rarely direct-sown; cuttings or transplants are the standard. Deadhead spent umbels weekly to maintain continuous bloom. Let soil dry slightly between waterings to prevent root rot. In zones 10–11 plants may be left in ground year-round or overwintered as houseplants.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Geraniums in Other Locations
Frequently Asked Questions
When should I plant Geraniums in Sonoma County, CA?
Sonoma County is in Zone 9b with an average last frost of February 26. Plan your Geraniums 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.
When should I plant Geraniums in Sonoma County, CA?
In Sonoma County, CA, plant Geraniums after the last frost (around February 26) and before the first frost (around November 26). Best results when soil holds above 50°F.
What growing zone is Sonoma County, CA for Geraniums?
Sonoma County sits in USDA Zone 9b. Geraniums grows reliably in zones 2a through 11b, so it's a good fit here.
Can Geraniums grow in Sonoma County's climate?
Yes — Geraniums grows well in Sonoma County's temperate climate. Sonoma County averages a 274-day frost-free season, with last frost around February 26 and first frost around November 26.
Your Sonoma County Garden Planner — Free
A 22-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.