When to Plant Onions in Wisconsin
Wisconsin spans USDA hardiness 4a to 6a (zones 4a to 6a on this page). Plant onions by your local frost date, not the calendar — pick your zone below for exact start-indoors, transplant, and harvest dates.
Jump to: Zone 4a · Zone 4b · Zone 5a · Zone 5b · Zone 6a
Onions planting calendar for Wisconsin, Zone 4a
Average last spring frost
May 15
Average first fall frost
September 20
Direct sow
Feb 20
Projected first harvest
Jun 10
Most onions mature in about 90 to 110 days depending on the variety. Full zone 4 guide (both 4a and 4b) →
Onions planting calendar for Wisconsin, Zone 4b
Average last spring frost
May 10
Average first fall frost
September 25
Direct sow
Feb 15
Projected first harvest
Jun 5
Most onions mature in about 90 to 110 days depending on the variety. Full zone 4 guide (both 4a and 4b) →
Onions planting calendar for Wisconsin, Zone 5a
Average last spring frost
May 5
Average first fall frost
October 1
Direct sow
Feb 10
Projected first harvest
May 31
Most onions mature in about 90 to 110 days depending on the variety. Full zone 5 guide (both 5a and 5b) →
Onions planting calendar for Wisconsin, Zone 5b
Average last spring frost
April 30
Average first fall frost
October 5
Direct sow
Feb 5
Projected first harvest
May 26
Most onions mature in about 90 to 110 days depending on the variety. Full zone 5 guide (both 5a and 5b) →
Onions planting calendar for Wisconsin, Zone 6a
Average last spring frost
April 25
Average first fall frost
October 10
Direct sow
Jan 31
Projected first harvest
May 21
Most onions mature in about 90 to 110 days depending on the variety. Full zone 6 guide (both 6a and 6b) →
Not sure which half-zone you're in? Set your ZIP in HomeSown for dates tuned to your exact location.
Varieties to grow
8 varieties of onions in the HomeSown library. Tap any for its full grow guide.
Common problems with onions
What to watch for, with identification and treatment for each
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