When to plant sweet marjoram in Milwaukee, Wisconsin

April 26 – May 10

Transplant outdoors · typical Milwaukee year

Climate basis: NOAA station West Allis, WI (USC00479046), 6 mi (10 km) from downtown Milwaukee (ZCTA 53202 centroid), elevation 723 ft, on the 1991–2020 climate normals. Transplant sweet marjoram outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (April 26). One year in ten still freezes after May 12.

Last spring freezeApril 261-in-10 after May 12

First fall freezeOctober 221-in-10 before Oct 7

Frost-free season≈ 177 daysmedian at 32°F

Hard freeze, 28°Apr 14 – Nov 1kills even hardy greens

USDA zone6a-10 to -5°F winter low — not frost timing

The Milwaukee year

Start seeds indoorsMar 1 – Mar 15

Transplant outdoorsApr 26 – May 10

Direct-sow outdoorsApr 12 – Apr 26

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 12

Sweet Marjoram in Milwaukee · freeze context from West Allis, WI, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Mar 1 – Mar 15

NC State's Extension Gardener Plant Toolbox starts marjoram seed indoors about 6 to 8 weeks before the last spring frost date, and Clemson HGIC gives the identical 6-to-8-week lead, so the two sources agree. Anchored to the median last spring freeze (Apr 26). NC State Extension, North Carolina Extension Gardener Plant Toolbox · Clemson University Cooperative Extension, Home & Garden Information Center

Transplant outdoors

Apr 26 – May 10

Clemson HGIC sets marjoram transplants out after the last killing frost and UMD Extension names marjoram among herbs planted outside after the danger of frost has passed; both agree, so the window opens at the last spring freeze. Anchored to the median last spring freeze (Apr 26). Clemson University Cooperative Extension, Home & Garden Information Center

Direct-sow outdoors

Apr 12 – Apr 26

NC State's Extension Gardener Plant Toolbox gives a point rule — sow seed directly outdoors about two weeks before the last spring frost date — which opens a two-week sowing span ending at the last freeze; note the transplant window for this tender herb is later. Anchored to the median last spring freeze (Apr 26). NC State Extension, North Carolina Extension Gardener Plant Toolbox

Variety assumption: Grown as an annual across most of the US; NC State's plant toolbox treats it as a tender perennial that is replaced each year in cold climates.

These windows describe typical years (1991–2020 climate normals), not this year's forecast. Freezes happen outside them — especially in frost pockets, valleys, and urban edges. Watch the forecast before committing tender plants.

This week, not a typical year:

Crop rule sources (2)

NC State Extension, North Carolina Extension Gardener Plant Toolbox: Origanum majorana (Knotted Marjoram, Marjoram, Pot Marjoram, Sweet Marjoram) (accessed 2026-07-25)
"To plant from seed, start seeds indoors about 6 to 8 weeks prior to the last spring frost date."
Clemson University Cooperative Extension, Home & Garden Information Center: Herbs (accessed 2026-07-25)
"Start seed indoors 6 to 8 weeks before planting or set transplants out after the last killing frost."

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