We’re going to break from the greenhouse topic for a brief interlude back into hardening off. Many of you might be wondering if there’s a minimum plant size, or maturity level, at which you can begin hardening off your plants.
Technically speaking, you can begin hardening off at any stage of plant growth, even the initial cotyledon stage. However, there’s inherent risks with hardening off very young plants as they have very little foliage and thus, any sunburn whatsoever can be fatal.
We harden off plenty of very young and highly immature plants. But, we do usually wait until at least those first true leaves start developing. We’re also exceptionally careful, introducing our plants to the sun in very low amounts initially. Typically an hour or two hours tops for the first several days. We’ll link to our hardening off article down in the comments if you didn’t catch our previous posts and want to know our exact hardening off process.
In many ways, we almost have grown to prefer hardening off plants when they’re younger. Larger plants, especially broadleaf plants, tend to have larger foliage that is more prone to sun burn. Getting the hardening process over early means we can maximize that sun-grown greenery, supercharged by the powerful sun.
But, there’s a risk trade off here. You have little room for error when hardening off plants that are very young, whereas more mature seedlings have higher risks of sun burn with those effects being less dangerous to the plant. You may find, like we did, that as you gain more experience, your tolerance of risk rises.
Lastly, we’ll close this topic by saying that we’ve begun the hardening off process for our tomatoes and frost sensitive plants! Our signal here is future forecasts that predict overnight temperatures that will remain above freezing. While it’s still likely we’ll dip below freezing again, and this risk remains until around our average last frost dates, we can be a lot more confident that our frost risks are significantly lessened in these conditions.
We’ll have more to say about this topic, I’m sure, but we wanted to fit this one in sooner than later. Many of you might be trying to seize some nice shoulder season days!
