Frost Date Math

When to Plant Peppers: Seed Starting and Transplant Dates

By Tam Vu · Updated

On this page
  1. What the source says about pepper seeds
  2. The math
  3. Three stations, same rules
  4. A more cautious reading
  5. Hardening off
  6. Sources

Peppers are a warm-season crop and one of the slower ones to start. The University of Idaho Extension guide gives them 6 to 9 weeks indoors and says warm-season plants can go into the garden about 1 to 3 weeks after the average date of last frost. Look up your date with the frost date tool.

What the source says about pepper seeds

Peppers
Ideal soil temperature for germination 75 to 85 °F
Days to germination 10 to 14
Weeks to grow indoors 6 to 9
Move outdoors about 1 to 3 weeks after the average last frost

Peppers take 10 to 14 days to sprout, against 7 to 14 for tomatoes, and need 6 to 9 weeks indoors against 5 to 9 for tomatoes.

The math

  • Move-out window = last frost + 1 week to last frost + 3 weeks.
  • Earliest start = earliest move-out date − 9 weeks.
  • Latest start = latest move-out date − 6 weeks.

Three stations, same rules

All dates use NOAA's 50% last freeze at 32 °F and a 2027 calendar.

Weather station Average last freeze (50%) Move peppers outdoors Start seeds indoors
Dallas-Fort Worth AP, Texas Mar 8 Mar 15 to Mar 29 Jan 11 to Feb 15
Port Columbus Intl AP, Ohio Apr 18 Apr 25 to May 9 Feb 21 to Mar 28
Denver Intl AP, Colorado May 5 May 12 to May 26 Mar 10 to Apr 14

Check one row: Columbus, April 18 + 1 week = April 25, + 3 weeks = May 9. April 25 − 9 weeks = February 21. May 9 − 6 weeks = March 28.

A more cautious reading

Counting from the 10% last freeze date (a freeze after it is unlikely) instead of the 50% date:

Weather station Last freeze (10%) Move peppers outdoors Start seeds indoors
Dallas-Fort Worth AP, Texas Mar 26 Apr 2 to Apr 16 Jan 29 to Mar 5
Port Columbus Intl AP, Ohio May 5 May 12 to May 26 Mar 10 to Apr 14
Denver Intl AP, Colorado May 19 May 26 to Jun 9 Mar 24 to Apr 28

This is not the extension guide's own rule, which counts from the average date. See what frost dates mean.

Hardening off

Seedlings grown indoors are soft. The guide says to acclimate them by moving the pots outside for longer periods each day, which usually takes at least a week.

Sources