When to Plant Brussels Sprouts in Franklin County, ID
Your May game plan for Franklin County, Idaho
Your Franklin County, Idaho garden is entering a new phase. Here's what's on the schedule for May and why each task matters now.
-
Time to transplant brussels sprouts
Pinch off the lowest leaves on each seedling before you plant — it reduces water loss while the roots catch up.
-
Seed brussels sprouts outdoors
Sow every 2 weeks for a continuous harvest. A single big planting means a single big glut.
Before June arrives, get these ready
- Starting indoors: brussels sprouts
Brussels sprouts are a cold-hardy brassica that produces miniature cabbage-like heads along a tall stalk. Flavor improves after a light frost.
Franklin County, Idaho is in USDA Zone 6a. The average last spring frost is May 19 and the first fall frost is October 3, giving you a growing season of approximately 137 days.
At an elevation of 7,665 feet, Franklin County receives approximately 18.5 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Brussels Sprouts during the growing season. With low rainfall, drip irrigation is essential for growing Brussels Sprouts successfully. Mulch heavily to conserve soil moisture.
Franklin County Soil Profile
Soil Type
Loam
Soil pH
6.7-7.7
Drainage
Well Drained
Plant Planting Risk Windows
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 Franklin County
How your county's soil matches Brussels Sprouts's growing requirements.
Soil pH
Your soil pH (6.7–7.7) overlaps with Brussels Sprouts's range (6.0–7.5), though not a perfect match.
Soil Texture
The loam soil in Franklin County is excellent for Brussels Sprouts — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.6%). Annual compost additions will help Brussels Sprouts.
How to Plant Brussels Sprouts
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Brussels Sprouts
Brussels Sprouts needs approximately 0.9 inches of water per week (3.9" per month). Here's how your county's rainfall compares month by month.
| Month | Brussels Sprouts Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.4" | 0" | ❄️ Dormant |
| Feb | — | 1.1" | 0" | ❄️ Dormant |
| Mar | — | 1.5" | 0" | ❄️ Dormant |
| Apr | — | 2" | 0" | ❄️ Dormant |
| May | 3.9" | 1.9" | 2" | 🚿 Regular watering |
| Jun | 3.9" | 1.3" | 2.6" | 🚿 Regular watering |
| Jul | 3.9" | 1.8" | 2.1" | 🚿 Regular watering |
| Aug | 3.9" | 2" | 1.9" | 💧 Light watering |
| Sep | 3.9" | 1.6" | 2.3" | 🚿 Regular watering |
| Oct | 3.9" | 1.8" | 2.1" | 🚿 Regular watering |
| Nov | — | 1.2" | 0" | ❄️ Dormant |
| Dec | — | 1.1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Franklin County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Brussels Sprouts 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.
Brussels Sprouts Planting Timeline — Franklin County, ID
Brussels Sprouts Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 14 | Apr 14 – Apr 28 |
| Transplant Outdoors | May 19 | May 19 – Jun 2 |
| Direct Sow | May 5 | May 5 – May 26 |
| Harvest | August 18 | Aug 18 – Oct 13 |
| Fall Sowing | July 25 | Jul 25 – Aug 8 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Transplant Outdoors Direct Sow |
| June | Transplant Outdoors |
| July | Fall Sowing |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.9"/week · 1-2 times/week
📅 Days to Maturity
90–130 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 6a
📆 Growing Season
137 days in Franklin County
Growing Tips for Brussels Sprouts in Franklin County
Direct sow Brussels Sprouts outdoors after May 19 in Franklin County when soil has warmed and frost danger has passed.
Your 137.0-day growing season in Franklin County is tight for Brussels Sprouts (90.0-130.0 days to maturity). Start indoors and choose early-maturing varieties.
Common pests for Brussels Sprouts in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
Franklin County receives only 18" of rain annually. Brussels Sprouts needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Start seeds indoors 12-14 weeks before first fall frost. Stake tall plants to prevent toppling. Remove lower leaves as sprouts develop to improve air circulation.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Brussels Sprouts in Other Locations
Frequently Asked Questions
When should I plant Brussels Sprouts in Franklin County, ID?
Franklin County is in Zone 6a with an average last frost of May 19. Plan your Brussels Sprouts planting based on this frost date — see the calendar above for exact timing.
What planting zone is Franklin County, ID?
Franklin County, Idaho is in USDA Hardiness Zone 6a. The average last spring frost is May 19 and first fall frost is October 3.
Your Franklin County Garden Planner — Free
A 24-page printable planner built for Franklin 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.