So you’ve sown your seeds. Been there. Now, it’s time to get hard, fool!
Hardening your seedlings is a requirement prior to transplanting them into their permanent homes, and you’ll want to begin the process a week or so before you plant them out. The process is fairly straight forward but does take some care and attention.
Up to this point, your seedlings have been babied. It’s time to show them a little tough love. On a mild day, with light wind and no rain, place your seed tray outside in a sheltered area. It must be out of direct sunlight. You can do this for a few hours the first day, bringing the seedlings inside at night. Gradually increase their exposure to sunlight over the coming days, adding a few hours each day.
Increasing wind exposure will also help strengthen the plants so that they’re less likely to buckle once they’re outside for good. Some people actually simulate this indoors by running their hand lightly over the tips of the plants a few times each day, while others place a small oscillating fan near their seedlings.
You may also want to gradually expose your seedlings to cool temperatures as well, though I’ve never found this to be a problem. I now situate my seedlings in a greenhouse window where they’re exposed to strong sun during the day and cooler temperatures at night, and as a result I no longer have to harden them off. If you can simulate these conditions, you may find yourself in a similar situation.