When to plant borage in St. Louis, Missouri

April 1 – April 15

Direct-sow outdoors · typical St. Louis year

Climate basis: NOAA station St Louis Sci Ctr, MO (USC00237452), 4 mi (7 km) from downtown St. Louis (ZCTA 63101 centroid), elevation 515 ft, on the 1991–2020 climate normals. Direct-sow borage from approximately the dates above, anchored to the median last spring 32°F freeze (April 1). One year in ten still freezes after April 18.

Last spring freezeApril 11-in-10 after Apr 18

First fall freezeNovember 41-in-10 before Oct 24

Frost-free season≈ 218 daysmedian at 32°F

Hard freeze, 28°Mar 22 – Nov 15kills even hardy greens

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

The St. Louis year

Start seeds indoorsFeb 18 – Mar 4

Direct-sow outdoorsApr 1 – Apr 15

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to Apr 18

Borage in St. Louis · freeze context from St Louis Sci Ctr, MO, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Feb 18 – Mar 4

Illinois Extension permits starting borage indoors but gives no lead time, so the offset comes from Virginia Cooperative Extension's herb publication — whose annual herb table lists borage — which sows small herb seed about six weeks before the last frost date. Anchored to the median last spring freeze (Apr 1). Virginia Cooperative Extension, Virginia Tech

Direct-sow outdoors

Apr 1 – Apr 15

Illinois Extension sows borage directly in the garden after frost is past, a point rule that opens a two-week sowing span at the last spring freeze. Anchored to the median last spring freeze (Apr 1). University of Illinois Extension · Virginia Cooperative Extension, Virginia Tech

Variety assumption: Virginia Cooperative Extension lists borage as a self-sowing annual; it resents root disturbance, so direct sowing is the usual method.

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)

University of Illinois Extension: Borage | Herbs (accessed 2026-07-25)
"Borage is easily grown from seed started indoors or directly sown in the garden after frost is past."
Virginia Cooperative Extension, Virginia Tech: Herb Culture and Use (Publication 426-420) (accessed 2026-07-25)
"In addition, many culinary herbs, such as tarragon, can only be propagated asexually; seed-grown plants lack the oils that give them flavor."

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