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When to Plant Tomatoes in Bannock County, ID

Bannock County, Idaho Zone 6a May

May to-do list for Bannock County, Idaho

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 23
Avg. first frost September 24
Soil temp (4") 42°F
Watering High
Pest pressure Low
Daylight 14.4 hrs
  1. Outdoor sowing time: tomatoes

    Thin ruthlessly once seedlings are up. Crowded roots mean smaller crops from every plant.

Get ahead of June
  • Transplants going out: tomatoes

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Tomatoes are the most popular home garden crop, available in thousands of varieties from tiny cherries to massive beefsteaks. They are warm-season plants needing full sun.

Bannock County, Idaho is in USDA Zone 6a. The average last spring frost is May 23 and the first fall frost is September 24, giving you a growing season of approximately 124 days.

At an elevation of 5,637 feet, Bannock County receives approximately 13.1 inches of rainfall annually with predominantly loam soil. Summer highs average 83°F, so choose short-season varieties of Tomatoes to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Tomatoes successfully. Mulch heavily to conserve soil moisture.

Bannock County, ID (Zone 6a) Short season
124 days
Last Spring Frost May 23
124 growing days
First Fall Frost September 24

Bannock County Soil Profile

Soil Type

Loam

Soil pH

6.7-8.1

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 15 Transplant: May 24 🍅 Harvest: Jul 26 – Oct 4
Recommended (50%) ✗ May not fit
Start indoors: Mar 28 Transplant: Jun 6 🍅 Harvest: Aug 8 – Oct 17
Safe Start (90%) ✗ May not fit
Start indoors: Apr 23 Transplant: Jul 2 🍅 Harvest: Sep 3 – Nov 12

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 Bannock County

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

Soil pH

Your soil pH (6.7–8.1) is more alkaline than Tomatoes prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

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

How to Plant Tomatoes

0.5"
Planting Depth
24"
Between Plants
36"
Between Rows

Succession Planting Tomatoes

2
successive plantings in your 124-day season

Sow every 6.9 weeks. Last sowing by Jul 01 to harvest before frost.

Plant Water Budget

Plant needs
1.2″/week
Rainfall provides
0.4″/week
You supply
0.9″/week
Watering frequency 2-3 times/week
Season total 1,002 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Tomatoes

Tomatoes needs approximately 1.2 inches of water per week (5.2" per month). Here's how your county's rainfall compares month by month.

Month Tomatoes Needs Rainfall You Supplement Action
Jan 1" 0" ❄️ Dormant
Feb 0.8" 0" ❄️ Dormant
Mar 1.1" 0" ❄️ Dormant
Apr 1.4" 0" ❄️ Dormant
May 5.2" 1.5" 3.7" 🚿 Regular watering
Jun 5.2" 0.9" 4.3" 🚿 Regular watering
Jul 5.2" 1.1" 4.1" 🚿 Regular watering
Aug 5.2" 1.4" 3.8" 🚿 Regular watering
Sep 5.2" 1" 4.2" 🚿 Regular watering
Oct 1" 0" ❄️ Dormant
Nov 1" 0" ❄️ Dormant
Dec 0.8" 0" ❄️ Dormant

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

Tomatoes 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.

Tomatoes needs ~888 GDD — county provides 1,519 GDD Excellent fit

Tomatoes Planting Timeline — Bannock County, ID

Tomatoes Planting Calendar

Activity When Date Range
Start Indoors March 28 Mar 28 – Apr 11
Transplant Outdoors June 6 Jun 6 – Jun 20
Direct Sow May 30 May 30 – Jun 20
Harvest August 8 Aug 8 – Oct 17

Plant 0.5" deep · 24" apart · Rows 36" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1.2"/week · 2-3 times/week

📅 Days to Maturity

60–85 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 6a

📆 Growing Season

124 days in Bannock County

Growing Tips for Tomatoes in Bannock County

Direct sow Tomatoes outdoors after May 23 in Bannock County when soil has warmed and frost danger has passed.

Common pests for Tomatoes in this region include tomato hornworm and aphids. Use row covers early in the season and inspect plants weekly.

Bannock County receives only 13" of rain annually. Tomatoes needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Start seeds indoors 6-8 weeks before last frost. Bury transplants deep to encourage rooting along the stem. Provide consistent moisture to prevent blossom end rot and cracking.

Recommended Tomatoes Varieties for Bannock County

Choose determinate, early-maturing varieties for your short season

Early Girl (52d) Stupice (55d) Glacier (55d) Sub Arctic Plenty (45d)

Companion Planting

Good Companions

Avoid Planting Near

  • Cabbage
  • Fennel
  • Potatoes

Check more plant combinations with our Companion Planting Checker →

🌾 Save Your Own Tomatoes Seeds
Life Cycle Annual
Pollination Self-Pollinating
How to Collect Scoop seeds from ripe fruit; ferment 2-3 days to remove gel coating.
Storage Store airtight; viable 4-6 years at 35°F, under 45% humidity.

Isolate 25 ft between varieties for purity. Use open-pollinated varieties for true-to-type seeds.

Frequently Asked Questions

When should I plant Tomatoes in Bannock County, ID?

Bannock County is in Zone 6a with an average last frost of May 23. Plan your Tomatoes planting based on this frost date — see the calendar above for exact timing.

What planting zone is Bannock County, ID?

Bannock County, Idaho is in USDA Hardiness Zone 6a. The average last spring frost is May 23 and first fall frost is September 24.

🌱

Your Bannock County Garden Planner — Free

A 24-page printable planner built for Bannock County (Zone 6a). 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 Bannock County, ID. 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.