PlantingWindowThe American Planting Almanac

When to plant borage in Boise, Idaho

May 17 – May 31

Direct-sow outdoors · typical Boise year

Climate basis: NOAA station Boise 7 N, ID (USC00101017), 6 mi (9 km) from downtown Boise (ZCTA 83702 centroid), elevation 3885 ft, on the 1991–2020 climate normals. Direct-sow borage from approximately the dates above, anchored to the median last spring 32°F freeze (May 17). One year in ten still freezes after June 10.

Last spring freezeMay 171-in-10 after Jun 10
First fall freezeOctober 121-in-10 before Sep 27
Frost-free season≈ 147 daysmedian at 32°F
Hard freeze, 28°Apr 27 – Oct 24kills even hardy greens
USDA zone7a0 to 5°F winter low — not frost timing

The Boise year

Start seeds indoorsApr 5 – Apr 19
Direct-sow outdoorsMay 17 – May 31
  • indoors under lights
  • in the garden
  • frost-free season
  • 1-in-10 years still freeze to Jun 10
Borage in Boise · freeze context from Boise 7 N, ID, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Apr 5 – Apr 19

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 (May 17). Virginia Cooperative Extension, Virginia Tech

Direct-sow outdoors

May 17 – May 31

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 (May 17). 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)

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