What to Plant in September in Zone 3

Garlic and shallots go in now, timed to the ground, not the frost

Garlic and shallot cloves need 4 to 6 weeks of root growth before the ground freezes hard, and that freeze, not the first light frost, is the number that actually sets the deadline here. Zone 3 ground typically locks up in mid-November, which puts the real planting window at late September into early October, well after that first frost has already come and gone. Push each clove root down 2 inches, pointed end up, spaced 6 inches apart.

Mulch the row with 3 to 4 inches of straw the same week you plant, before the ground has a chance to freeze under bare soil. Going in too early, while soil is still warm from summer, can push top growth that a hard freeze then damages, so there is no advantage to planting the moment the calendar flips to this month.

Check the bed again once the ground has frozen solid, usually in November, and add a second layer of mulch if the first has thinned or blown loose. Cloves that get a full 4 to 6 weeks in cool, unfrozen soil come up bigger next July than ones rushed in too soon or crowded past that window.

Pull in what the frost will not spare

Any winter squash still on the vine should come off before a hard freeze blackens the skin, even if the stem has not fully dried down yet. Cure them somewhere at 80 to 85 degrees for 10 days, then move to a spot in the low 50s for storage.

Check the root cellar or the coolest closet shelf now, before it is full. A shelf reading above 50 degrees this month will run warmer once household heat kicks on in November, and warm storage is the fastest way to lose a squash harvest to rot.