When to plant sweet marjoram in Louisville, Kentucky

March 31 – April 14

Transplant outdoors · typical Louisville year

Climate basis: NOAA station Louisville Mcalpine, KY (USC00154955), 3 mi (4 km) from downtown Louisville (ZCTA 40202 centroid), elevation 440 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 (March 31). One year in ten still freezes after April 14.

Last spring freezeMarch 311-in-10 after Apr 14

First fall freezeNovember 91-in-10 before Oct 31

Frost-free season≈ 225 daysmedian at 32°F

Hard freeze, 28°Mar 18 – Nov 20kills even hardy greens

USDA zone7a0 to 5°F winter low — not frost timing

The Louisville year

Start seeds indoorsFeb 3 – Feb 17

Transplant outdoorsMar 31 – Apr 14

Direct-sow outdoorsMar 17 – Mar 31

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to Apr 14

Sweet Marjoram in Louisville · freeze context from Louisville Mcalpine, KY, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Feb 3 – Feb 17

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 (Mar 31). NC State Extension, North Carolina Extension Gardener Plant Toolbox · Clemson University Cooperative Extension, Home & Garden Information Center

Transplant outdoors

Mar 31 – Apr 14

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 (Mar 31). Clemson University Cooperative Extension, Home & Garden Information Center

Direct-sow outdoors

Mar 17 – Mar 31

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 (Mar 31). 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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