When to Plant Onion in Gregory County, SD
Your May planting checklist for Gregory County, South Dakota
We've pulled the most time-sensitive tasks for Gregory County, South Dakota this May and put them front and centre. Tackle them in order.
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Get onion in the ground
Frost risk is low now in Gregory County, South Dakota. If you've been covering beds overnight, you can stop.
A few tasks this May that'll pay off in June
- Starting indoors: 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.
Gregory County, South Dakota is in USDA Zone 5a. The average last spring frost is May 10 and the first fall frost is October 6, giving you a growing season of approximately 149 days.
At an elevation of 668 feet, Gregory County receives approximately 34.5 inches of rainfall annually with predominantly loam soil. Summer highs average 82°F, so choose short-season varieties of Onion to ensure they mature before fall.
Gregory County Soil Profile
Soil Type
Loam
Soil pH
6.4-7.4
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 Gregory County
How your county's soil matches Onion's growing requirements.
Soil pH
Your soil pH (6.4–7.4) overlaps with Onion's range (6.0–7.0), though not a perfect match.
Soil Texture
The loam soil in Gregory County is excellent for Onion — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.2%). Annual compost additions will help Onion.
How to Plant Onion
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
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 | — | 0.8" | 0" | ❄️ Dormant |
| Feb | — | 1.3" | 0" | ❄️ Dormant |
| Mar | — | 2.1" | 0" | ❄️ Dormant |
| Apr | — | 3.4" | 0" | ❄️ Dormant |
| May | 4.3" | 5.8" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 5" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 4.8" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 4.1" | 0.2" | 💧 Light watering |
| Sep | 4.3" | 3.3" | 1" | 💧 Light watering |
| Oct | 4.3" | 1.9" | 2.4" | 🚿 Regular watering |
| Nov | — | 1" | 0" | ❄️ Dormant |
| Dec | — | 0.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Gregory 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 — Gregory County, SD
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 5 | Apr 5 – Apr 19 |
| Transplant Outdoors | May 10 | May 10 – May 24 |
| Direct Sow | April 26 | Apr 26 – May 17 |
| Harvest | August 9 | Aug 9 – Sep 27 |
| Fall Sowing | July 28 | Jul 28 – Aug 11 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Fall Sowing |
| August | Fall Sowing Harvest |
| September | Harvest |
| 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: acceptable
🗺️ USDA Zone
Zone 5a
📆 Growing Season
149 days in Gregory County
Growing Tips for Onion in Gregory County
Direct sow Onion outdoors after May 10 in Gregory 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 Gregory County, SD?
Gregory County is in Zone 5a with an average last frost of May 10. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Gregory County, SD?
Gregory County, South Dakota is in USDA Hardiness Zone 5a. The average last spring frost is May 10 and first fall frost is October 6.
Your Gregory County Garden Planner — Free
A 24-page printable planner built for Gregory County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.