PlantAlong

When to plant garlic in zone 6a

Plant for fall between Oct 24 and Oct 31. That is 1-2 weeks after zone 6a's median first frost, Oct 171. Across most of zone 6a that date falls between Oct 12 and Nov 7.

Why a range: zone 6a is defined by winter lows, not frost dates. Its ZIP codes have median first frosts from Oct 5 to Oct 242, so a single zone date can be weeks off for you. The rule comes from University of Wisconsin–Madison Division of Extension, Wisconsin Horticulture, written for WI and applied here to zone 6a's frost dates.

Last reviewed
Stations
924
ZIP codes
4,375
Photo: Chris F / Pexels
These dates use the typical last frost for the whole zone. Your ZIP code gives a closer answer.
  1. Plant for fallWisconsin
  • Start indoors
  • Plant outdoors
  • Range across the zone
  • Frost-free season (median)
  • Spring frost risk (90% to 10%)
  • Fall frost risk (10% to 90%)
Figure 1. Garlic in zone 6a. Dark bars: at the zone's median frost dates. Pale bars: across most of the zone's ZIP codes. Hatched blue: where the zone's last and first frosts fall.
Fall planting
Oct 241-2 weeks after first frost

Five digits. The calendar is computed on your device.

What each source says, applied to zone 6a

The same frost dates give different answers depending on whose rule you follow. These are all the published rules we hold for garlic, worked out at zone 6a's median frost dates.

Table 1. Garlic rules from every source, at zone 6a's median last frost (Apr 28) and first frost (Oct 17).
SourceWhatRuleZone 6a median
Minnesota3Plant for fall1-2 weeks after first frostOct 24 – Oct 31
Wisconsin1Used abovePlant for fall1-2 weeks after first frostOct 24 – Oct 31
Texas A&M (E-502)4Plant for fall4-6 weeks before first frostSep 5 – Sep 19

Frost across zone 6a

  1. Last spring frostmedian Apr 28
  2. First fall frostmedian Oct 17
  • Frost-free season (median)
Figure 2. Frost dates across zone 6a, from 924 NOAA stations matched to 4,375 ZIP codes.

Sources

  1. University of Wisconsin–Madison Division of Extension, Wisconsin Horticulture, Garlic, Allium sativum, Rev: 10/2023. Retrieved 2026-11-02.
  2. NOAA National Centers for Environmental Information, U.S. Climate Normals 2020: U.S. Annual/Seasonal Climate Normals (1991-2020), 2021. Retrieved 2026-11-02.
  3. University of Minnesota Extension, Fruit and Vegetable News blog, Tips for garlic planting season, Page shows October 15, 2026; URL path says 2021/10 (unresolved). Retrieved 2026-11-02.
  4. Texas AgriLife Extension Service, The Texas A&M System, Texas Home Vegetable Gardening Guide (E-502), 2/09. Retrieved 2026-11-02.