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When to Plant Borage in Calaveras County, CA

Calaveras County, California Zone 9a May

Top priorities for Calaveras County, California gardeners in May

Your garden in Calaveras County, California is working on a schedule, even when you're not. Here's where you should be this May.

Avg. last frost April 8
Avg. first frost November 12
Soil temp (4") 68°F
Watering Critical
Pest pressure High
Daylight 14.1 hrs
  1. Start borage under lights

    Starting these indoors now means sturdy transplants ready the moment your soil warms up.

  2. Bring in the borage

    Taste as you pick. The first ripe produce is the best feedback loop you'll get all season.

Before June arrives, get these ready
  • 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.

Calaveras County, California is in USDA Zone 9a. The average last spring frost is April 8 and the first fall frost is November 12, giving you a growing season of approximately 218 days.

At an elevation of 2,363 feet, Calaveras County receives approximately 25 inches of rainfall annually with predominantly loam soil. Summer highs average 83°F, so choose short-season varieties of Borage to ensure they mature before fall.

Calaveras County, CA (Zone 9a) Long season
218 days
Last Spring Frost April 8
218 growing days
First Fall Frost November 12

Calaveras County Soil Profile

Soil Type

Loam

Soil pH

6.5-7.6

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (148 days to spare)
Start indoors: Feb 2 Transplant: Feb 23 🍅 Harvest: Apr 20 – Jun 8
Recommended (50%) ✓ Fits season (120 days to spare)
Start indoors: Mar 11 Transplant: Apr 1 🍅 Harvest: May 27 – Jul 15
Safe Start (90%) ✓ Fits season (120 days to spare)
Start indoors: Apr 10 Transplant: May 1 🍅 Harvest: Jun 26 – Aug 14

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 Calaveras County

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

Soil pH

Your soil pH (6.5–7.6) is more alkaline than Borage prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.9%). 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 218-day season

Sow every 5.7 weeks. Last sowing by Sep 13 to harvest before frost.

For a dedicated fall crop, sow by Sep 17.

Plant Water Budget

Plant needs
0.5″/week
Rainfall provides
0.5″/week
You supply
0.0″/week
Watering frequency Only during dry spells
Season total 43 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — 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 5.4" 0" ❄️ Dormant
Feb 4.8" 0" ❄️ Dormant
Mar 4" 0" ❄️ Dormant
Apr 2.2" 2.4" 0" ✅ Rainfall sufficient
May 2.2" 0.7" 1.5" 🚿 Regular watering
Jun 2.2" 0.2" 2" 🚿 Regular watering
Jul 2.2" 0" 2.2" 🚿 Regular watering
Aug 2.2" 0" 2.2" 🚿 Regular watering
Sep 2.2" 0.3" 1.9" 🚿 Regular watering
Oct 2.2" 1" 1.2" 🚿 Regular watering
Nov 2.2" 2.3" 0" ✅ Rainfall sufficient
Dec 3.9" 0" ❄️ Dormant

Water needs are for active growing months only (Apr–Nov in Calaveras 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 ~674 GDD — county provides 2,670 GDD Excellent fit

Borage Planting Timeline — Calaveras County, CA

Borage Planting Calendar

Activity When Date Range
Start Indoors March 11 Mar 11 – Mar 25
Transplant Outdoors April 1 Apr 1 – Apr 15
Direct Sow March 18 Mar 18 – Apr 8
Harvest May 27 May 27 – Jul 15
Fall Sowing September 17 Sep 17 – Oct 1

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

Month-by-Month Timeline

MonthActivities
January
February
March Start Indoors Direct Sow
April Transplant Outdoors Direct Sow
May Harvest
June Harvest
July Harvest
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: too_alkaline

🗺️ USDA Zone

Zone 9a

📆 Growing Season

218 days in Calaveras County

Growing Tips for Borage in Calaveras County

Direct sow Borage outdoors after April 08 in Calaveras 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 Calaveras County, CA?

Calaveras County is in Zone 9a with an average last frost of April 8. Plan your Borage planting based on this frost date — see the calendar above for exact timing.

What planting zone is Calaveras County, CA?

Calaveras County, California is in USDA Hardiness Zone 9a. The average last spring frost is April 8 and first fall frost is November 12.

🌱

Your Calaveras County Garden Planner — Free

A 24-page printable planner built for Calaveras County (Zone 9a). 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 Calaveras 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.