2026

May

How to Harden Off Your Seedlings before you plant them, and why it’s important 

WHAT IS HARDENING OFF? 

Hardening off is a gradual process that helps seedlings, such as toma-toes, peppers, and other warm season crops and flowers, transition from the controlled environment indoors to the more challenging conditions outdoors. This step is essential because outdoor conditions—like increased sunlight, wind, and fluctuating tempera-tures—are very different from what the plants are used to inside your home or greenhouse. 

WHY IS HARDENING OFF IMPORTANT? 

If you move your plants directly from a warm, protected space to the garden without giving them time to adjust, they can suffer severe setbacks, and some may not survive at all. Whether you’ve grown your plants from seed or purchased them from a greenhouse, every seedling benefits from this acclimation period. 

THE HARDENING OFF PROCESS 

The process is straightforward but requires patience and time. You should plan to spend about a week preparing your young plants for transplantation. 

Day 1: Place your seedlings in a sheltered, shady location, such as under a tree or on a patio, for 5 to 6 hours. Bring them back indoors at night. 

Day 2: Move your plants to a spot where they get morning sun and afternoon shade. Leave them out for 6 to 7 hours to help them adjust to direct sunlight. 

Day 3: Increase their exposure to direct sun and let your trans-plants remain outside after dark. 

Day 4: If nighttime temperatures stay above 50° F, leave the starter plants outside all night. Continue this routine on days five and six but bring plants indoors if temperatures drop. 

By the end of this period, your transplants should be ready to move into the garden. 

FINAL STEPS AND TIPS 

Even after hardening off, monitor the weather forecast, as late frosts can damage your plants. Our average last frost date is May 13, but this can vary. Keep a frost blanket or floating row cover handy for protection—avoid using plastic covers. If your plants are small enough, covering them with a box can help guard against frost. 

For the easiest transition from containers to the garden, choose a cloudy day to plant your seedlings. During the hardening off period, remember to keep your plants well-watered, as they will dry out more quickly outdoors. Moist soil helps protect against temperature changes better than dry soil. 

Michael Morris