When to plant Onion in Johnson County, IN
Johnson County sits in USDA Zone 6a. Plant Onion between March 29 (after last frost on April 12) and April 19. A second sowing from August 13 to August 27 extends the harvest into fall.
When to Plant Onion in Johnson County, IN
Your June game plan for Johnson County, Indiana
June is a pivotal month for Johnson County, Indiana gardens. Focus on these tasks first and you'll set up the rest of the season for success.
July prep starts now
- First harvests: onion
Onions are a fundamental kitchen staple available in yellow, white, and red varieties. Choose long-day, short-day, or intermediate types based on your latitude.
Johnson County, Indiana is in USDA Zone 6a. The average last spring frost is April 12 and the first fall frost is October 22, giving you a growing season of approximately 193 days.
At an elevation of 1,324 feet, Johnson County receives approximately 36.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 90°F, providing good warmth for Onion during the growing season.
Johnson County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-7
Drainage
Well Drained
Onion 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 Johnson County
How your county's soil matches Onion's growing requirements.
Soil pH
Your soil pH (6.2–7.0) is within Onion's preferred range (6.0–7.0).
Soil Texture
The silt loam soil in Johnson County is excellent for Onion — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (5.1%) — Onion will thrive.
How to Plant Onion
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Onion Water Budget
Monthly Watering Guide for Onion
Onion needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Onion Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.7" | 0" | ❄️ Dormant |
| Feb | — | 1.6" | 0" | ❄️ Dormant |
| Mar | — | 2.3" | 0" | ❄️ Dormant |
| Apr | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| May | 4.3" | 4.6" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 4.1" | 0.2" | 💧 Light watering |
| Jul | 4.3" | 4.4" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 4" | 0.3" | 💧 Light watering |
| Sep | 4.3" | 3.1" | 1.2" | 💧 Light watering |
| Oct | 4.3" | 2.9" | 1.4" | 💧 Light watering |
| Nov | — | 2.2" | 0" | ❄️ Dormant |
| Dec | — | 2.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Johnson County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Onion 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.
Onion Planting Timeline — Johnson County, IN
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 8 | Mar 8 – Mar 22 |
| Transplant Outdoors | April 12 | Apr 12 – Apr 26 |
| Direct Sow | March 29 | Mar 29 – Apr 19 |
| Harvest | July 12 | Jul 12 – Aug 30 |
| Fall Sowing | August 13 | Aug 13 – Aug 27 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | — |
| July | Harvest |
| August | Fall Sowing Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: ideal
🗺️ USDA Zone
Zone 6a
📆 Growing Season
193 days in Johnson County
Growing Tips for Onion in Johnson County
Direct sow Onion outdoors after April 12 in Johnson County when soil has warmed and frost danger has passed.
Common pests for Onion in this region include onion maggots and thrips. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 8-10 weeks before transplanting. Match day-length type to your latitude. Stop watering when tops begin to fall over and cure bulbs for 2-3 weeks before storage.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Johnson County, IN?
Johnson County is in Zone 6a with an average last frost of April 12. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Johnson County, IN?
Johnson County, Indiana is in USDA Hardiness Zone 6a. The average last spring frost is April 12 and first fall frost is October 22.
When should I plant Onion in Johnson County, IN?
In Johnson County, IN, plant Onion after the last frost (around April 12) and before the first frost (around October 22). Best results when soil holds above 50°F.
What growing zone is Johnson County, IN for Onion?
Johnson County sits in USDA Zone 6a. Onion grows reliably in zones 3a through 10b, so it's a good fit here.
Can Onion grow in Johnson County's climate?
Yes — Onion grows well in Johnson County's temperate climate. Johnson County averages a 193-day frost-free season, with last frost around April 12 and first frost around October 22.
Your Johnson County Garden Planner — Free
A 22-page printable planner built for Johnson 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.