When to Plant Milk Thistle in Iowa
Iowa spans USDA hardiness 4b to 6a (zones 4b to 6a on this page). Plant milk thistle by your local frost date, not the calendar — pick your zone below for exact start-indoors, transplant, and harvest dates.
Jump to: Zone 4b · Zone 5a · Zone 5b · Zone 6a
Milk Thistle planting calendar for Iowa, Zone 4b
Average last spring frost
May 10
Average first fall frost
September 25
Direct sow
May 24
Milk Thistle needs about 150 days to mature — longer than Zone 4b typically stays frost-free, so it likely won't reliably ripen there outdoors without a head start indoors or season extension. Full zone 4 guide (both 4a and 4b) →
Milk Thistle planting calendar for Iowa, Zone 5a
Average last spring frost
May 5
Average first fall frost
October 1
Direct sow
May 19
Milk Thistle needs about 150 days to mature — longer than Zone 5a typically stays frost-free, so it likely won't reliably ripen there outdoors without a head start indoors or season extension. Full zone 5 guide (both 5a and 5b) →
Milk Thistle planting calendar for Iowa, Zone 5b
Average last spring frost
April 30
Average first fall frost
October 5
Direct sow
May 14
Milk Thistle needs about 150 days to mature — longer than Zone 5b typically stays frost-free, so it likely won't reliably ripen there outdoors without a head start indoors or season extension. Full zone 5 guide (both 5a and 5b) →
Milk Thistle planting calendar for Iowa, Zone 6a
Average last spring frost
April 25
Average first fall frost
October 10
Direct sow
May 9
Projected first harvest
Oct 6
Milk Thistle is ready to harvest in about 150 days. 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
1 variety of milk thistle in the HomeSown library. Tap any for its full grow guide.
Common problems with milk thistle
What to watch for, with identification and treatment for each
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