When to plant bell pepper in Denver

Where are you growing?

Tight fit

Not realistic in greenhouse

Comfortable in a cold frame

Bell pepper in Denver is doable with planning outdoors. 76 suitable days are enough for fast varieties (60 days) but not slow ones (85 days).

Start indoors: April 3 – April 4
Transplant outside: June 12 – June 13
Harvest: August 11 – August 26
Season vs crop: 76 grow days vs 60–85 needed
Typical frost (last spring – first fall): April 21 – September 8

Bell pepper in Denver is doable with planning outdoors. 76 suitable days are enough for fast varieties (60 days) but not slow ones (85 days).

Start seeds indoors April 3 – April 4, transplant June 12 – June 13, and a faster variety can still make a harvest outdoors (76 suitable growing days cover the 60-day short end).

Planting conditions

Start indoors
Grow 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 row76

Days to harvest60–85 days from transplant

Apr 3 – Apr 4

Start indoors

Apr 5 – Jun 4

Grow indoors

Jun 5 – Jun 11

Harden off

June 12

Transplant outside

Jun 13 – Aug 10

Grow outdoors

Aug 11 – Aug 26

Harvest

Activity	Window	Notes
Start indoors	Apr 3 – Apr 4	Sow indoors before the outdoor window.
Grow indoors	Apr 5 – Jun 4	Seedlings grow indoors until harden or transplant.
Harden off	Jun 5 – Jun 11	Acclimate seedlings outdoors before planting.
Transplant outside	June 12	Move plants outside on this day (start of the plant-out window).
Grow outdoors	Jun 13 – Aug 10	Plants grow outdoors until harvest.
Harvest	Aug 11 – Aug 26	Expected 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 (70 – 84 °F) and tolerable (55 – 95 °F) ranges.

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 21

Safer last spring frostApril 21

Typical first fall frostSeptember 8

Safer first fall frostSeptember 8

Frost-free days139

Earliest indoor seed startApril 3

Latest indoor seed startApril 4

Transplant outdoorsJune 12 – June 13

Direct sow windownot recommended here

Suitable growing windowJune 12 – August 26 (76 days)

Expected harvestAugust 11 – August 26

How these dates are judged

Ideal conditions: Daytime air from 70 – 84 °F.
Suitable conditions: Daytime air from 55 – 95 °F.
Last frost and first frost: Typical spring and fall frost dates for Denver, shown in the key dates.
Days to harvest: 60–85 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 Bell pepper: Jun 12 – Aug 26 (76 days)

Planting window for Bell pepper: Jun 12 – Jun 13 (2 days)

Usually too cold: Sep 7 – Dec 31

Outdoors: weekly temperatures and windows

Temperatures across the year for Denver. 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.

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 24 · Jun 8 – Jun 14

Average 53 to 82 °F · Possible 42 to 94 °F

Growing: too cold

Planting: too cold

A week is in range when its average low and high sit inside the tolerance band 55 to 95 °F; it is suitable when that average range also overlaps the ideal 70 to 84 °F band and possible readings stay within 32 °F to 95 °F. Crossing a possible limit, or missing the ideal band, makes it tolerable; any chance of frost (possible low below 32 °F) makes it too cold. 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 Denver

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 39.70, -105.00, 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 Bell pepper 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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