When to Plant Milk Thistle in Zone 4
In USDA zone 4a, plant outdoors May 29 to September 20. (4a shown here — see 4a and 4b dates separately below.)
Milk Thistle planting calendar for USDA Zone 4a
Average last spring frost
May 15
Average first fall frost
September 20
Direct sow
May 29
Milk Thistle needs about 150 days to mature — longer than zone 4atypically stays frost-free, so it likely won't reliably ripen there outdoors without a head start indoors or season extension.
Milk Thistle planting calendar for USDA 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 4btypically stays frost-free, so it likely won't reliably ripen there outdoors without a head start indoors or season extension.
Not sure whether you're in 4a or 4b? 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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