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When to Plant Borage in Ventura County, CA

Ventura County, California Zone 10a May

Your May game plan for Ventura County, California

A quick May briefing for Ventura County, California gardeners — what's urgent, what's next, and what can wait.

Avg. last frost March 18
Avg. first frost November 15
Soil temp (4") 77°F
Watering Critical
Pest pressure High
Daylight 13.8 hrs
  1. Harvest borage as they ripen

    If you can't use it all right away, check the food-preservation section of your planner.

Get ahead of June
  • First harvests: borage

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Borage is a self-seeding annual herb with star-shaped blue flowers that attract pollinators. Its leaves have a cucumber-like flavor and the flowers are edible.

Ventura County, California is in USDA Zone 10a. The average last spring frost is March 18 and the first fall frost is November 15, giving you a growing season of approximately 242 days.

At an elevation of 2,094 feet, Ventura County receives approximately 19.4 inches of rainfall annually with predominantly loam soil. Summer highs average 88°F, providing good warmth for Borage during the growing season. With low rainfall, drip irrigation is essential for growing Borage successfully. Mulch heavily to conserve soil moisture.

Ventura County, CA (Zone 10a) Long season
242 days
Last Spring Frost March 18
242 growing days
First Fall Frost November 15

Ventura County Soil Profile

Soil Type

Loam

Soil pH

6-7.7

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (153 days to spare)
Start indoors: Feb 1 Transplant: Feb 22 🍅 Harvest: Apr 19 – Jun 7
Recommended (50%) ✓ Fits season (144 days to spare)
Start indoors: Feb 18 Transplant: Mar 11 🍅 Harvest: May 6 – Jun 24
Safe Start (90%) ✓ Fits season (143 days to spare)
Start indoors: Mar 15 Transplant: Apr 5 🍅 Harvest: May 31 – Jul 19

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 Ventura County

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

Soil pH

Your soil pH (6.0–7.7) overlaps with Borage's range (6.0–7.0), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.3%). Annual compost additions will help Borage.

How to Plant Borage

0.5"
Planting Depth
8"
Between Plants
12"
Between Rows

Fall planting: Sow 8 weeks before your first frost date for a fall harvest.

Succession Planting Borage

5
successive plantings in your 242-day season

Sow every 5.7 weeks. Last sowing by Sep 16 to harvest before frost.

For a dedicated fall crop, sow by Sep 20.

Plant Water Budget

Plant needs
0.5″/week
Rainfall provides
0.3″/week
You supply
0.2″/week
Watering frequency Only during dry spells
Season total 422 gal / 100 sq ft
Drought risk

Water stress score is 10/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Borage

Borage needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.

Month Borage Needs Rainfall You Supplement Action
Jan 3.8" 0" ❄️ Dormant
Feb 4.4" 0" ❄️ Dormant
Mar 2.2" 3.2" 0" ✅ Rainfall sufficient
Apr 2.2" 1.5" 0.7" 💧 Light watering
May 2.2" 0.6" 1.6" 🚿 Regular watering
Jun 2.2" 0.1" 2.1" 🚿 Regular watering
Jul 2.2" 0" 2.2" 🚿 Regular watering
Aug 2.2" 0" 2.2" 🚿 Regular watering
Sep 2.2" 0.2" 2" 🚿 Regular watering
Oct 2.2" 0.8" 1.4" 🚿 Regular watering
Nov 2.2" 1.7" 0.5" 💧 Light watering
Dec 3.1" 0" ❄️ Dormant

Water needs are for active growing months only (Mar–Nov in Ventura County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Borage 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.

Borage needs ~880 GDD — county provides 3,872 GDD Excellent fit

Borage Planting Timeline — Ventura County, CA

Borage Planting Calendar

Activity When Date Range
Start Indoors February 18 Feb 18 – Mar 4
Transplant Outdoors March 11 Mar 11 – Mar 25
Direct Sow February 25 Feb 25 – Mar 18
Harvest May 6 May 6 – Jun 24
Fall Sowing September 20 Sep 20 – Oct 4

Plant 0.5" deep · 8" apart · Rows 12" apart

Month-by-Month Timeline

MonthActivities
January
February Start Indoors Direct Sow
March Start Indoors Transplant Outdoors Direct Sow
April
May Harvest
June Harvest
July
August
September Fall Sowing
October Fall Sowing
November
December

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.5"/week · Only during dry spells

📅 Days to Maturity

50–60 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 10a

📆 Growing Season

242 days in Ventura County

Growing Tips for Borage in Ventura County

Direct sow Borage outdoors after March 18 in Ventura County when soil has warmed and frost danger has passed.

General growing tips

Direct sow in spring as borage does not transplant well. Allow some plants to go to seed for next year. Young leaves are best; older leaves become bristly.

Companion Planting

Good Companions

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Borage in Ventura County, CA?

Ventura County is in Zone 10a with an average last frost of March 18. Plan your Borage planting based on this frost date — see the calendar above for exact timing.

What planting zone is Ventura County, CA?

Ventura County, California is in USDA Hardiness Zone 10a. The average last spring frost is March 18 and first fall frost is November 15.

🌱

Your Ventura County Garden Planner — Free

A 24-page printable planner built for Ventura 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.

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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 Ventura County, CA. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.