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When to plant cabbage in Ottawa

How to grow CabbageOttawa climate
Where are you growing?

Tight fit

Not realistic in greenhouse

Tight fit in a cold frame

Cabbage in Ottawa is doable with planning outdoors. 67 suitable days are enough for fast varieties (60 days) but not slow ones (100 days).

Start indoors
March 6 – April 30
Transplant outside
April 17 – June 11
Harvest
June 16 – September 19
Season vs crop
67 grow days vs 60–100 needed
Typical frost (last spring – first fall)
May 13 – October 30

Cabbage in Ottawa is doable with planning outdoors. 67 suitable days are enough for fast varieties (60 days) but not slow ones (100 days).

Start seeds indoors March 6 – April 30, then transplant April 17 – June 11 so the crop can finish outdoors.

Planting conditions

Cabbage planting activities across the year: Start indoors, Harden off, Transplant outside, Grow outdoors, HarvestJFMAMJJASOND~May 13~Oct 30
  • Start indoors
  • Harden off
  • Transplant outside
  • Grow outdoors
  • Harvest
Local activity windows for this place and growing method. Blue fill is usually too cold for this plant. Dashed lines are typical last and first frost.
Suitable growing days in a row67
Days to harvest60–100 days from transplant
Mar 6 – Apr 30
Start indoors
Apr 10 – Apr 16
Harden off
April 17
Transplant outside
Apr 18 – Jun 15
Grow outdoors
Jun 16 – Sep 19
Harvest
ActivityWindowNotes
Start indoorsMar 6 – Apr 30Sow indoors before the outdoor window.
Harden offApr 10 – Apr 16Acclimate seedlings outdoors before planting.
Transplant outsideApril 17Move plants outside on this day (start of the plant-out window).
Grow outdoorsApr 18 – Jun 15Plants grow outdoors until harvest.
HarvestJun 16 – Sep 19Expected harvest from typical days to harvest.
Blue fill is usually too cold for this plant. Dashed lines are typical last and first frost. 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 (15 – 24 °C) and tolerable (4 – 27 °C) ranges.

Cabbage planting and growing weeks in OttawaJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECPlantingGrowing
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 frostMay 13
Safer last spring frostMay 13
Typical first fall frostOctober 30
Safer first fall frostOctober 30
Frost-free days169
Earliest indoor seed startMarch 6
Latest indoor seed startApril 30
Transplant outdoorsApril 17 – June 11
Direct sow windownot recommended here
Suitable growing windowApril 17 – June 22 (67 days)
Expected harvestJune 16 – September 19

How these dates are judged

Ideal conditions
Daytime air from 15 – 24 °C.
Suitable conditions
Daytime air from 4 – 27 °C.
Last frost and first frost
Typical spring and fall frost dates for Ottawa, shown in the key dates.
Days to harvest
60–100 days from transplant, 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 Cabbage: Apr 17 – Jun 22 (67 days)

Planting window for Cabbage: Apr 17 – Jun 11 (56 days)

Usually too cold: Nov 2 – Dec 31

Outdoors: weekly temperatures and windows

Temperatures across the year for Ottawa. 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−40 °C−40 °F−30 °C−22 °F−20 °C−4 °F−10 °C14 °F0 °C32 °F10 °C50 °F20 °C68 °F30 °C86 °F40 °C104 °FTolerable 4–27 °CTolerable 39–81 °FIdeal 15–24 °CIdeal 59–75 °FWindowGrowingApr 17 – Jun 22PlantingApr 17 – Jun 11Last frost ~May 13First frost ~Oct 30
  • 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 16 · Apr 13 – Apr 19

Average 3 to 12 °C · Possible −3 to 24 °C

Growing: too cold

Planting: too cold

A week is in range when its average low and high sit inside the tolerance band 4 to 27 °C; it is suitable when that average range also overlaps the ideal 15 to 24 °C band and possible readings stay within 4 °C to 27 °C. Crossing a possible limit, or missing the ideal band, makes it tolerable; a possible low below 4 °C 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 Ottawa

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 45.41, -75.70, 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 Cabbage 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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