What type vegetable plant often needs to be hardened off

about 7-10 days

It usually takes about 7-10 days to get the tomato and pepper seedlings fully hardened off.

Explanation:

Guide to Hardening-off

Harden off gradually, so that seedlings become accustomed to strong sunlight, cool nights and less-frequent watering over a 7-10 day period. On a mild day, start with 2-3 hours of sun in a sheltered location. Protect seedlings from strong sun, wind, hard rain and cool temperatures.