So, we talked about our hardening off strategy yesterday. Let’s get into the mechanics of what we’re doing! Should you ignore this advice, your plants WILL perish when you put them outside. There’s some well spread myths around this, too, so even you seasoned gardeners may want to pay attention.
Hardening off is the process of gradually introducing our plants to the power of the sun. The gist is that the sun is magnitudes more powerful than our indoor grow lights. Plants can effectively get a sun burn, just like us humans. The difference is, for plants, that sun burn can be lethal.
We’ve tried a lot of hardening off methods. We worked hard to find the minimal amount of time we could harden off for pretty much every kind of plant out there. Big plants, little plants, single stalk plants, broadleaf plants, cold loving plants and warm loving plants. The gamut. Essentially a universal strategy.
We settled on one day at 1 hour, two days at 2 hours, one day at 4 hours and finally a fifth day at 8 hours. After this, your plants can be safely outside, assuming temperatures remain adequate. Should you want a bunch more info, we have our full hardening off guide linked in the comments!
This process can be improved, with the biggest difference coming from more days at lower amounts of time. An additional day at one or two hours can make a difference, especially for broadleaf plants like squash and nasturtium. That said, these plants will still work with our “minimal” process, but you might get a tiny bit of sun burn. Technically, you can harden off as slowly as you like, so feel free to add more days if you think its appropriate.
We’re generally looking for days above 40F for most of our plants. While you can go a bit lower, and we’ve certainly done it, we’re rarely in enough of a hurry to push against crummy weather. When it comes to warm loving veggies (peppers, squash, cucumber, etc.), you really want days that are above 50F. If you get thwarted by weather for a day or two, you can simply pick up where you left off. But, if several days go by due to weather or maybe personal schedule, it’s usually good to at least repeat the last step.
Many of you may have read or heard that you have to harden off on cloudy days. Or maybe do so in the shade. That’s a garden myth! With the schedule we outlined here, you can harden off in broad daylight without issue. Again, the key is keeping the first few days short!
You might be wondering about what’s going on physiologically with the plant during this process. Basically, it’s building up carbohydrates and thicker cell walls that allow the plant to protect itself from the sun’s light energy and ultra-violet rays. You can think of it like a natural sun tan lotion. Plants grown under the sun from day one don’t need this since they start this process from the moment the cotyledon is produced.
So, that’s how we harden off! If you do something different, let us know how you roll! We’re always curious about what other folks do!
