When to Plant Onion in Sullivan County, PA
Top priorities for Sullivan County, Pennsylvania gardeners in July
July is a pivotal month for Sullivan County, Pennsylvania gardens. Focus on these tasks first and you'll set up the rest of the season for success.
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Start harvesting onion
If you can't use it all right away, check the food-preservation section of your planner.
Coming up in August — start thinking about
- First harvests: onion
- Fall sowing: 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.
Sullivan County, Pennsylvania is in USDA Zone 6a. The average last spring frost is May 1 and the first fall frost is October 17, giving you a growing season of approximately 169 days.
At an elevation of 560 feet, Sullivan County receives approximately 44.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 87°F, providing good warmth for Onion during the growing season.
Sullivan County Soil Profile
Soil Type
Silt Loam
Soil pH
4.9-6.8
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 Sullivan County
How your county's soil matches Onion's growing requirements.
Soil pH
Your soil pH (4.9–6.8) is more acidic than Onion prefers (6.0–7.0). Add garden lime to raise pH.
Soil Texture
The silt loam soil in Sullivan County is excellent for Onion — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.9%). Annual compost additions will help Onion.
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 | — | 3.1" | 0" | ❄️ Dormant |
| Feb | — | 2.6" | 0" | ❄️ Dormant |
| Mar | — | 4.2" | 0" | ❄️ Dormant |
| Apr | — | 4.1" | 0" | ❄️ Dormant |
| May | 4.3" | 4.4" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 4.3" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 4.6" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 3.8" | 0.5" | 💧 Light watering |
| Sep | 4.3" | 3.3" | 1" | 💧 Light watering |
| Oct | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| Nov | — | 3.1" | 0" | ❄️ Dormant |
| Dec | — | 3.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Sullivan 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 — Sullivan County, PA
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 27 | Mar 27 – Apr 10 |
| Transplant Outdoors | May 1 | May 1 – May 15 |
| Direct Sow | April 17 | Apr 17 – May 8 |
| Harvest | July 31 | Jul 31 – Sep 18 |
| Fall Sowing | August 8 | Aug 8 – Aug 22 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Harvest |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Natural rainfall sufficient
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: too_acidic
🗺️ USDA Zone
Zone 6a
📆 Growing Season
169 days in Sullivan County
Growing Tips for Onion in Sullivan County
Direct sow Onion outdoors after May 01 in Sullivan 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 Sullivan County, PA?
Sullivan County is in Zone 6a with an average last frost of May 1. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Sullivan County, PA?
Sullivan County, Pennsylvania is in USDA Hardiness Zone 6a. The average last spring frost is May 1 and first fall frost is October 17.
Your Sullivan County Garden Planner — Free
A 22-page printable planner built for Sullivan 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.