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When to Plant Scallions in Siskiyou County, CA

Siskiyou County, California Zone 8a May

May to-do list for Siskiyou County, California

If you only do a handful of things in the garden this May, make it these. They're sequenced around your zone's frost timing.

Avg. last frost May 15
Avg. first frost October 1
Soil temp (4") 67°F
Watering Critical
Pest pressure Moderate
Daylight 14.3 hrs
  1. Set out scallions seedlings

    Harden off for 7 days — a little more sun each day — before planting. That's the difference between a seedling that thrives and one that stalls.

  2. Plant scallions from seed, right in the garden

    Rake a smooth bed, make a shallow furrow, drop seeds at the spacing on the packet, water gently, walk away.

June prep starts now
  • Starting indoors: scallions

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Scallions (green onions) are mild-flavored alliums harvested for their slender green tops and white bases. They are quick-growing and perfect for succession planting.

Siskiyou County, California is in USDA Zone 8a. The average last spring frost is May 15 and the first fall frost is October 1, giving you a growing season of approximately 139 days.

At an elevation of 251 feet, Siskiyou County receives approximately 36 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 84°F, so choose short-season varieties of Scallions to ensure they mature before fall. Sandy soil warms quickly in spring — great for early planting — but Scallions will need more frequent watering and organic matter to retain nutrients.

Siskiyou County, CA (Zone 8a) Short season
139 days
Last Spring Frost May 15
139 growing days
First Fall Frost October 1

Siskiyou County Soil Profile

Soil Type

Sandy Loam

Soil pH

6-6.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (54 days to spare)
Start indoors: Apr 1 Transplant: May 6 🍅 Harvest: Jul 1 – Jul 29
Recommended (50%) ✓ Fits season (55 days to spare)
Start indoors: Apr 10 Transplant: May 15 🍅 Harvest: Jul 10 – Aug 7
Safe Start (90%) ✓ Fits season (44 days to spare)
Start indoors: May 14 Transplant: Jun 18 🍅 Harvest: Aug 13 – Sep 10

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 Siskiyou County

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

Soil pH

Your soil pH (6.0–6.9) is within Scallions's preferred range (6.0–7.0).

Soil Texture

Sandy soil in Siskiyou County warms quickly in spring but drains fast. Scallions will need more frequent watering and regular compost additions to retain nutrients.

Organic Matter

Organic matter is moderate (2.5%). Annual compost additions will help Scallions.

How to Plant Scallions

0.5"
Planting Depth
6"
Between Plants
12"
Between Rows

Fall planting: Sow 10 weeks before your first frost date for a fall harvest.

Succession Planting Scallions

3
successive plantings in your 139-day season

Sow every 5.7 weeks. Last sowing by Jul 23 to harvest before frost.

For a dedicated fall crop, sow by Jul 23.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
1.1″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft

Monthly Watering Guide for Scallions

Scallions needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Scallions Needs Rainfall You Supplement Action
Jan 7.3" 0" ❄️ Dormant
Feb 7.1" 0" ❄️ Dormant
Mar 5.3" 0" ❄️ Dormant
Apr 3.3" 0" ❄️ Dormant
May 4.3" 1" 3.3" 🚿 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" 0.4" 3.9" 🚿 Regular watering
Oct 4.3" 1.6" 2.7" 🚿 Regular watering
Nov 3.1" 0" ❄️ Dormant
Dec 6.7" 0" ❄️ Dormant

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

Scallions 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.

Scallions needs ~780 GDD — county provides 1,807 GDD Excellent fit

Scallions Planting Timeline — Siskiyou County, CA

Scallions Planting Calendar

Activity When Date Range
Start Indoors April 10 Apr 10 – Apr 24
Transplant Outdoors May 15 May 15 – May 29
Direct Sow May 1 May 1 – May 22
Harvest July 10 Jul 10 – Aug 7
Fall Sowing July 23 Jul 23 – Aug 6

Plant 0.5" deep · 6" apart · Rows 12" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · Natural rainfall sufficient

📅 Days to Maturity

50–70 days

🧪 Soil pH

Needs 6–7 · Your soil: ideal

🗺️ USDA Zone

Zone 8a

📆 Growing Season

139 days in Siskiyou County

Growing Tips for Scallions in Siskiyou County

Direct sow Scallions outdoors after May 15 in Siskiyou County when soil has warmed and frost danger has passed.

Sandy soil in Siskiyou County dries quickly — mulch Scallions with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.

Common pests for Scallions in this region include onion maggots and thrips. Use row covers early in the season and inspect plants weekly.

General growing tips

Direct sow every 3 weeks for continuous harvest. Thin to 1 inch apart or grow in clusters. Harvest when pencil-thick by pulling or cutting at soil level.

Companion Planting

Good Companions

Avoid Planting Near

  • Peas
  • Green Beans

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Scallions in Siskiyou County, CA?

Siskiyou County is in Zone 8a with an average last frost of May 15. Plan your Scallions planting based on this frost date — see the calendar above for exact timing.

What planting zone is Siskiyou County, CA?

Siskiyou County, California is in USDA Hardiness Zone 8a. The average last spring frost is May 15 and first fall frost is October 1.

🌱

Your Siskiyou County Garden Planner — Free

A 24-page printable planner built for Siskiyou County (Zone 8a). 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 Siskiyou 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.