Mississippi · zones 8a–9a
When to plant onions in Mississippi.
Sow or transplant between Jan 3 to Feb 16 in a typical year, keyed to Mississippi's median last frost around Mar 13. A second, fall sowing fits Sep 14 to Oct 26. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Onions dates for a typical Mississippi season.
1 · Start indoors
Nov 22 to Jan 5
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Jan 3 to Feb 16
Keyed to the ~Mar 13 last frost. Sow 0.5" deep, 4" apart.
Fall round
Sep 14 to Oct 26
Counted back from the ~Nov 9 first frost.
Harvest
~95 days later
~0.5 lb per plant over ~1 weeks.
Mississippi spans more than one climate: Zone 8 is the most common zone, but the state runs 8a to 9a. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
In Mississippi: watch for
The pests that find onions here.
With about 241 frost-free days, onion, bulb spends longer in the ground here than in most of the country, which widens the window in which onion thrips can find it. Scout weekly from midseason and act on the first signs.
Silvery streaks and curled leaf tips in hot spells.
Organic fix: Insecticidal soap or neem; hang sticky traps.
Seedlings wilt; white maggots in the bulb base.
Organic fix: Float a row cover over the row; rotate beds each year.
Pale patches with fuzzy gray growth in damp weather.
Organic fix: Space for airflow, water early in the day, spray neem.
White rot
Yellowing and dieback, then wilt; fluffy white mold at the bulb base and roots so rotted the plant lifts straight out.
Organic fix: No cure once it is in the soil. Plant clean stock, never follow onions with onions, and keep infested soil off tools and boots.
Your season math: Mississippi gives onions about 241 frost-free days, and it needs roughly 95 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting onions in Mississippi: questions
When should I plant onions in Mississippi?+
In a typical Mississippi year, sow onions or set out transplants between Jan 3 to Feb 16, keyed to the state's median last frost around Mar 13. There's also a fall window: Sep 14 to Oct 26. Your exact dates shift with your ZIP code and microclimate.
When do I start onions seeds indoors in Mississippi?+
Start seeds inside about 6 weeks before set-out: roughly Nov 22 to Jan 5 for a typical Mississippi season.
What USDA zone is Mississippi?+
Mississippi spans zones 8a–9a, mostly zone 8. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many onions plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.