When to Plant Onion in McPherson County, SD
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.
McPherson County, South Dakota is in USDA Zone 3b. The average last spring frost is May 11 and the first fall frost is September 27, giving you a growing season of approximately 139 days.
At an elevation of 637 feet, McPherson County receives approximately 21.4 inches of rainfall annually with predominantly loam soil. Summer highs average 79°F, so choose short-season varieties of Onion to ensure they mature before fall.
McPherson County Soil Profile
Soil Type
Loam
Soil pH
6.7-7.9
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.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Onion Planting Timeline — McPherson County, SD
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 30 | Mar 30 – Apr 13 |
| Transplant Outdoors | May 11 | May 11 – May 25 |
| Direct Sow | May 4 | May 4 – May 25 |
| Fall Sowing | July 5 | Jul 5 – Jul 19 |
| Harvest | August 10 | Aug 10 – Sep 14 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Fall Sowing |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Moderate — regular watering
Days to Maturity
90–120 days
Soil pH
6 – 7
USDA Zone
Zone 3b
Growing Season
139 days
Growing Tips for McPherson County
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
Level Up Your Garden
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in McPherson County, SD?
McPherson County is in Zone 3b with an average last frost of May 11. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is McPherson County, SD?
McPherson County, South Dakota is in USDA Hardiness Zone 3b. The average last spring frost is May 11 and first fall frost is September 27.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help McPherson County gardeners in Zone 3b organize planting dates, track what's growing, and never miss a planting window.
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