Hardening off is the process of toughening up your tiny, fragile seedlings, before you transplant them and leave them outside at the mercy of the elements. It’s too early to think about putting your tender pepper or tomato plants outside for a while yet, but you can start hardening off anything you’ve started inside that is cold hardy, such as cabbage, kale, spinach, broccoli, or peas. Many people direct seed these cold hardy plants, rather than starting them indoors. You can get a couple of weeks jump on the season by starting your brassicas inside, but if you don’t have the space, or you have enough on your plate protecting your tomato seedlings from your cat, then direct sowing the cold hardy crops is fine. You can plant anything cold tolerant as soon as you can work your soil. Maybe don’t plant all your seeds at once, just in case we get a late blast of winter! Make sure you check to see what crops are cold tolerant too! Peas, for example, are cold tolerant. Beans on the other hand will shrivel and die immediately if it gets to zero degrees.
Even the best set of grow lights cannot come close to the strength of the sun outside. In addition to the intense light, the tender seedlings will face wind, rain, and possibly drastic temperature fluctuations once they are outside. Give yourself a week or two to harden off your seedlings. Two weeks will give you a few days grace in case there is some extreme weather one day. Put your plants outside, out of direct sun and wind, for an hour or two. Initially you can put them in a plastic tote, or against a wall of the house, or wherever they are protected. Every day add an hour or two. As they spend more time outside, let them experience short periods of wind and sun. Eventually, gradually, your seedlings will have adapted to life outside! There are a few things to watch out for. The most important is time. Don’t forget about the poor things! The best way to harden off your seedlings is gradually! Even the most well-cared-for seedlings that have been hardened off with dedication and planning will still show a bit of transplant shock. Try to plant them out on a day without extreme sun, wind, or rain. Water well, remembering that most plants are happier being watered at their roots. Give them a bit of compost, and mulch. If you’ve never tried mulch, give it a go. It saves weeding, keeps water in the soil, and breaks down, providing organic matter to your soil.
Hardening off your seedlings is a pain in the neck! Is there anyone who likes running plants in and out of the house? Worrying about how much sun or wind they are getting? Hollering to the kids to “Get the plants in!!” when a sudden extreme downpour begins.
This is a good time to hit your gardening friends up for their orphaned seedlings, as most gardeners plant way too much, and get tired or overwhelmed during hardening off time! Just assume that the orphaned seedling you got from your friend still needs a bit of hardening off!
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