When to plant chili pepper in Denver

In Denver, typical last spring frost is May 8 and typical first fall frost is October 13. Typical last spring frost: May 8. Chili pepper in Denver is not realistic outdoors: 0 suitable days are fewer than the 60 days this plant usually needs.

Chili pepper

How to grow Chili pepper Denver climate Weekly temperatures and windows

Where are you growing?

Not realistic outdoors

Not realistic in greenhouse

Tight fit in a cold frame

Chili pepper in Denver is doable with planning under fleece. 85 suitable days are enough for fast varieties (60 days) but not slow ones (100 days).

Start indoors: March 26 – April 30
Transplant outside: May 28 – July 2
Harvest: July 27 – September 27
Season vs crop: 85 grow days vs 60–100 needed
Typical frost (last spring – first fall): May 2 – October 23

Chili pepper in Denver is doable with planning under fleece. 85 suitable days are enough for fast varieties (60 days) but not slow ones (100 days).

Start seeds indoors March 26 – April 30, then transplant May 28 – July 2 so the crop can finish under fleece.

Estimate. Protection varies with the cover, the weather and how you vent it.

Fleece adds about 1–4 °C on frosty nights, depending on its weight. Remove it on warm days.

Fleece also cuts light: about 5–10 % for light fleece, up to 50–70 % for heavy grades. Take it off by day once frosts are over.

Cover dates are modelled from weather-model data using published greenhouse studies. They are not measured in your greenhouse. A max–min thermometer inside will tell you more.

Typical last frost estimate range May 3 – April 22, depending on the cover and the night.

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 row85

Days to harvest60–100 days from transplant

Mar 26 – Apr 30

Start indoors

May 1 – May 20

Grow indoors

May 21 – May 27

Harden off

May 28

Transplant outside

May 29 – Jul 26

Grow outdoors

Jul 27 – Sep 27

Harvest

Activity	Window	Notes
Start indoors	Mar 26 – Apr 30	Sow indoors before the outdoor window.
Grow indoors	May 1 – May 20	Seedlings grow indoors until harden or transplant.
Harden off	May 21 – May 27	Acclimate seedlings outdoors before planting.
Transplant outside	May 28	Move plants outside on this day (start of the plant-out window).
Grow outdoors	May 29 – Jul 26	Plants grow outdoors until harvest.
Harvest	Jul 27 – Sep 27	Expected harvest from typical days to harvest.

Start indoors
Grow indoors
Harden off
Transplant outside
Grow outdoors
Harvest

Blue fill is usually too cold for this plant. Dashed lines are typical last and first frost (35 seasons (1991–2025)). Adjust a week or two for your conditions.

Protected frost and sowing dates are modelled estimates from weather-model data and published greenhouse studies, not measured in your greenhouse. A max–min thermometer inside will tell you more.

Planting and growing across the year

Planting is the sow / plant-out window. Growing is daytime air versus this plant’s ideal (21 – 32 °C70 – 90 °F21 – 32 °C (70 – 90 °F)) and tolerable (16 – 35 °C61 – 95 °F16 – 35 °C (61 – 95 °F)) ranges, from modelled cover temperatures for the growing method you selected.

Ideal / plantable
Tolerable
Too cold
Too hot
Outside window

Planting uses sow / plant-out rules; growing shows daytime air against this plant’s ideal and tolerable ranges.

Key dates

Typical last spring frostMay 2

Low-risk last spring frostMay 14

Typical first fall frostOctober 23

Low-risk first fall frostSeptember 27

Frost-free days173

Earliest indoor seed startMarch 26

Latest indoor seed startApril 30

Transplant outdoorsMay 28 – July 2

Direct sow windownot recommended here

Suitable growing windowMay 28 – August 20 (85 days)

Expected harvestJuly 27 – September 27

How these dates are judged

Ideal conditions: Daytime air from 21 – 32 °C70 – 90 °F21 – 32 °C (70 – 90 °F).
Suitable conditions: Daytime air from 16 – 35 °C61 – 95 °F16 – 35 °C (61 – 95 °F).
Last frost and first frost: Typical spring and fall frost dates for Denver, 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. Air ratings on the weekly chart colour only weeks inside that same window — see weekly temperatures and windows.

Other plants for Denver

Calculated by Plan & Plant. Method. Data 35 seasons (1991–2025).

Frost and suitability dates are typical figures from climate statistics.

Based on 35 years (1991–2025) of ERA5-Land data from Open-Meteo, for an area of about 10 km. Typical dates, not a guarantee.

Dates for Denver use ERA5-Land cell 39.70, -105.00. How we calculated this · Algorithm 2026-10-season-10.

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