GROWING TIPS
How to Harden New Plantlings
Sierra Leeper | January 9, 2026
Moving to a new place always takes a little bit of adjusting, and the same is true for plants! While plants are resilient, they can also sometimes be a little sensitive and need a period of adapting to new circumstances. In gardening, this adjustment period is called hardening.
Hardening is the process of transitioning a plant from a comfortable, protected indoor environment to a variable outside environment where the plant will be exposed to sunlight, weather, and changing temperatures for the first time. Hardening plantlings allows plants to adjust to their new environment without getting shocked or stunted and works well for purchased transplants or any seedlings that have been started indoors.
Your plantlings have been grown in our greenhouse in Southern California, and then have been transported in a dark box for a day or two, so you can imagine that these conditions are very different from what they might experience in their new home in your garden. Let’s harden our plantlings to give them everything they need to adjust well to their big move!
HOW TO HARDEN:
Step 1: As soon as your box arrives, open it and place your plantlings upright in the trays they came in, adding about ¼” - ½” of water to the bottom of the tray.
Step 2: Set the trays outside in indirect sunlight for about 5 hours a day, making sure to bring them inside at night.
Step 3: Repeat this process for 1-2 days, and make sure that there is always water in your tray throughout the hardening process.
By getting water and sunshine while your plantlings are still in their trays, you are slowly introducing them to their new surroundings of your backyard. Once they have had a couple of days to adapt to their new environment, you’ll be ready to plant them permanently!
ADDITIONAL NOTES:
Plantlings need stable outdoor conditions to harden properly. If it is below 45° Fahrenheit, there are harsh winds, or it is raining or snowing, do not harden your plantlings outside. These harsh conditions can cause them to die early. Instead, harden your plants inside under a grow light. Once it reaches 45° outside or it has stopped raining or snowing, and your plants have hardened indoors, you can put plants in the ground.
The same goes for if the weather is too hot; If it is over 80° Fahrenheit, harden your plants early in the morning before it gets too hot and bring them inside when the temperature reaches 80° or higher.
Hardening your plants is easy, it just takes a little bit of patience and intentionality. It’s an important practice to give your plants the support they need to have a successful move and a thriving garden season!
Happy Hardening!
