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When to plant hardneck garlic in Seattle

How to grow Hardneck garlicSeattle climate
Where are you growing?

Comfortable

Hardneck garlic in Seattle is a good fit outdoors. Planted in autumn, harvested next summer (about 7–9 months).

When to plantOctober 25 – December 5

Harvest
210–270 days from planting
Season vs crop
312 grow days vs 210–270 needed
Typical frost (last spring – first fall)
April 2 – October 25

Hardneck garlic in Seattle is a good fit outdoors. Planted in autumn, harvested next summer (about 7–9 months).

Planting conditions

Hardneck garlic planting activities across the year: Direct sowJFMAMJJASOND~Apr 2~Oct 25
  • Direct sow
Local activity windows for this place and growing method. Dashed lines are typical last and first frost.
Suitable growing days in a row312
Days to harvest210–270 days from planting
Oct 25 – Dec 5
Direct sow
ActivityWindowNotes
Direct sowOct 25 – Dec 5Plant outdoors in this window.
Based on average frost dates. Adjust a week or two for your conditions.

Planting and growing across the year

Planting is the sow / plant-out window. Growing is daytime air versus this plant’s ideal (63 – 73 °F) and tolerable (23 – 86 °F) ranges.

Hardneck garlic planting and growing weeks in SeattleJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECPlantingGrowing
Planting uses sow / plant-out rules (frost, soil germination, night, and last-sow): green when plantable, blue diagonal when nights or soil are too cold, amber cross-hatch when too hot, faint for other calendar limits. Growing shows daytime air against this plant’s ideal and tolerable ranges across the year.

Key dates

Typical last spring frostApril 2
Safer last spring frostApril 2
Typical first fall frostOctober 25
Safer first fall frostOctober 25
Frost-free days205
Outdoor sow dateOctober 25
Direct sow windowOctober 25 – December 5
Suitable growing windowOctober 25 – September 1 (312 days)

How these dates are judged

Ideal conditions
Daytime air from 63 – 73 °F.
Suitable conditions
Daytime air from 23 – 86 °F.
Last frost and first frost
Typical spring and fall frost dates for Seattle, shown in the key dates.
Days to harvest
210–270 days from planting, from typical days to harvest.
Sowing window
Dated sow and harvest bars use frost dates, soil minima, night limits, and last-sow count-back from typical crop timing. The year strip and weekly chart use the same window: air ratings only colour weeks inside it.

Growing window for Hardneck garlic: Oct 25 – Sep 1 (312 days)

Planting window for Hardneck garlic: Oct 25 – Dec 5 (42 days)

Outdoors: weekly temperatures and windows

Temperatures across the year for Seattle. Shaded bands are this plant’s ideal and tolerable daytime air ranges. Growing is daytime air suitability; Planting is sow / plant-out conditions (same colour language). Window brackets mark each stretch.

JanFebMarAprMayJunJulAugSepOctNovDec−20 °C−4 °F−10 °C14 °F0 °C32 °F10 °C50 °F20 °C68 °F30 °C86 °F40 °C104 °FTolerable -5–30 °CTolerable 23–86 °FIdeal 17–23 °CIdeal 63–73 °FWindowGrowingOct 25 – Sep 1PlantingOct 25 – Dec 5Last frost ~Apr 2First frost ~Oct 25
  • Ideal range
  • Tolerable range
  • Possible min to max
  • Average min to max
  • Suitable
  • Tolerable
  • Too cold
  • Too hot

Selected week · tap a week or use the arrows

Week 1 · Jan 1 – Jan 4

Average 37 to 45 °F · Possible 13 to 54 °F

Growing: tolerable

Planting: too cold

A week is in range when its average low and high sit inside the tolerance band 23 to 86 °F; it is suitable when that average range also overlaps the ideal 63 to 73 °F band and possible readings stay within 23 °F to 86 °F. Crossing a possible limit, or missing the ideal band, makes it tolerable; a possible low below 23 °F makes it tolerable. When a sowing window is calculated, weeks outside that window are uncoloured even if air is in range.

Based on average frost dates.

Show all 53 weeks
Cover method weekly charts

Outdoor weekly chart is above. Open a cover chart only if you grow under fleece, a cold frame, or an unheated greenhouse.

Other plants for Seattle

Calculated by Plan & Plant · Method · Data 2019–2026

Frost and suitability dates are typical figures from climate statistics. Microclimates vary; they are not a guarantee.

How we calculated this
  • Data: ERA5-Land via Open-Meteo, cell 47.60, -122.30, years 2019–2026 (not a 30-year climate normal yet).
  • Typical and safer dates: Typical last frost is the date after which half of winters in this sample had no more frost; safer is later in the sample so fewer winters still frosted.
  • Crop rule: Local windows for Hardneck garlic from frost dates, temperature ratings, and crop timing rules.
  • Confidence: Provisional — short or thin sample for this place.
  • Full methodology (algorithm 2026-10-season-6).

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