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When to plant Geraniums in Isleton, CA

Isleton's 293-day season only supports one Geraniums planting per year. Sow between January 15 and January 29 for the best chance at full maturity before December 1.

When to Plant Geraniums in Isleton, CA

Sacramento County, California Zone 9b July

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Avg. last frost February 12
Avg. first frost December 1
Soil temp (4") 92°F
Watering Critical
Pest pressure High
Daylight 14.4 hrs
  1. It's harvest week for geraniums

    The more you pick, the more the plant produces. Letting fruit overripen tells the plant it's time to stop.

August will be here before you know it — start on
  • First harvests: geraniums

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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.

Isleton, California is in USDA Zone 9b. The average last spring frost is February 12 and the first fall frost is December 1, giving you a growing season of approximately 292 days.

At an elevation of 263 feet, Sacramento County receives approximately 33.2 inches of rainfall annually with predominantly loam soil. Summer highs average 90°F, providing good warmth for Geraniums during the growing season.

Annual Blooms in Multi-season Pollinator-friendly Deer-resistant Good for cutting Fragrant
Isleton, CA (Zone 9b) Year-round
292 days
Last Spring Frost February 12
292 growing days
First Fall Frost December 1

Isleton Soil Profile

Soil Type

Loam

Soil pH

6.4-7.1

Drainage

Well Drained

Geraniums Planting Risk Windows

Early Start (70% safe) ✓ Fits season (65 days to spare)
Start indoors: Nov 17 Transplant: Dec 29 🌸 Bloom: Mar 9 – Sep 21
Recommended (50%) ✓ Fits season (54 days to spare)
Start indoors: Dec 4 Transplant: Jan 15 🌸 Bloom: Mar 26 – Oct 8
Safe Start (90%) ✓ Fits season (20 days to spare)
Start indoors: Jan 26 Transplant: Mar 9 🌸 Bloom: May 18 – Nov 30

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 Isleton

How your county's soil matches Geraniums's growing requirements.

Soil pH

Your soil pH (6.4–7.1) overlaps with Geraniums's range (6.0–7.0), though not a perfect match.

Soil Texture

The loam soil in Sacramento County is excellent for Geraniums — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (2.4%). Annual compost additions will help Geraniums.

How to Plant Geraniums

0.1"
Planting Depth
12"
Between Plants
14"
Between Rows

Succession Planting Geraniums

4
successive plantings in your 292-day season

Sow every 8 weeks. Last sowing by Aug 23 to harvest before frost.

Geraniums Water Budget

Plant needs
1.0″/week
Rainfall provides
0.5″/week
You supply
0.6″/week
Watering frequency 1-2 times/week
Season total 1,640 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — 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 6.1" 0" ❄️ Dormant
Feb 4.3" 7.5" 0" ✅ Rainfall sufficient
Mar 4.3" 5.7" 0" ✅ Rainfall sufficient
Apr 4.3" 2.5" 1.8" 💧 Light watering
May 4.3" 0.8" 3.5" 🚿 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" 0.3" 4" 🚿 Regular watering
Oct 4.3" 1.4" 2.9" 🚿 Regular watering
Nov 4.3" 2.7" 1.6" 💧 Light watering
Dec 4.3" 5.9" 0" ✅ Rainfall sufficient

Water needs are for active growing months only (Feb–Dec in Sacramento 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 needs ~1,488 GDD — county provides 5,127 GDD Excellent fit

Geraniums Planting Timeline — Isleton, CA

Geraniums Planting Calendar

Activity When Date Range
Start Indoors December 4 Dec 4 – Dec 18
Transplant Outdoors January 15 Jan 15 – Jan 29
Bloom March 26 Mar 26 – Oct 8

Plant 0.1" deep · 12" apart · Rows 14" apart

Month-by-Month Timeline

MonthActivities
January Transplant Outdoors
February
March Bloom
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 · 1-2 times/week

📅 Days to Maturity

70–100 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 9b

📆 Growing Season

292 days in Sacramento County

Growing Tips for Geraniums in Isleton

Direct sow Geraniums outdoors after February 12 in Sacramento County when soil has warmed and frost danger has passed.

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 →

When should I plant Geraniums in Isleton, CA?

In Isleton, CA, plant Geraniums after the last frost (around February 12) and before the first frost (around December 1). Best results when soil holds above 50°F.

What growing zone is Isleton, CA for Geraniums?

Isleton sits in USDA Zone 9b. Geraniums grows reliably in zones 2a through 11b, so it's a good fit here.

Can Geraniums grow in Isleton's climate?

Yes — Geraniums grows well in Isleton's temperate climate. Isleton averages a 293-day frost-free season, with last frost around February 12 and first frost around December 1.

🌱

Your Sacramento County Garden Planner — Free

A 22-page printable planner built for Sacramento 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 Sacramento County, CA. Local conditions may vary. Last updated: July 2026.