Homegardening video How to Successfully Harden Off tomato Seedlings bychokri -December 21, 2017 0 Hardening off is the process of slowly acclimating young plants or seedlings to a new environment. In other words, hardening off is a way for gardeners to gradually condition their plants to the comparatively harsh conditions of the outdoors. Tags: gardening video Hardening off seedlings tomato Vegetables video Facebook Twitter