As temperatures warm up, crocus and daffodils lift themselves toward the sun, for those who have started seedlings indoors, the question often comes, now what?
What does it mean to harden off before transplanting?
This question comes up often this time of year.
Hardening off is literally hardening your seedling up to be ready to be out in the big outside world of your garden.
Like human babies, they have been nurtured indoors and kept in safe, protected spaces. Also, like human babies, you don’t lay them out on a blanket in full sun without protection and leave them there to fend for themselves.
Hardening off seedling fosters your seedling so they are able to withstand…
- Full sun, which is way stronger than your grow lights.
- Heavy rains that could batter and destroy young leaves.
- High winds that can rip tender leaves.
For us gardeners, hardening off a seedlings is a quicker process than raising children.
Can I Harden off seedlings quickly?
Generally, the process takes two weeks, or less.
My students have often heard me say it can be the most time-consuming part of starting seeds indoors yourself. But, don’t despair, it is not hard and you can do it around your work schedule.
You might ask, can I skip this step? Of course you can, but you are taking a risk of your seedlings dying, and why would you want to do that when you took the time to start them indoors?
Before you transplant the seedlings you started indoors, harden them off so they can thrive in your garden.
The hardening off process tends to take less time for spring crops than for summer ones. For this post, I am concentrating on spring crops, I can address, summer, fall and winter crops in later posts.
That said, the general idea is the same.
The first consideration is how different is it outside than inside. The bigger the temperature and light difference, the longer it takes to harden off your seedlings.
How long it takes depends on these differences or similarities.
How to Harden off Seedlings Before Planting
Remember that outdoor full sun is very different from indoor lights of any kind. It is much stronger. Yet, in spring the sun is still lower in the sky, therefore the sun is not as intense as it is in the long hot days of summer.
Steps for hardening off spring crops:
Start by putting your spring seedlings; such as lettuce, kale, cabbage and broccoli 🥦, outdoors in shade, or on a cloudy day for four hours.
Gradually give your seedlings full sun. Start with one or two hours. The cooler the temps, the longs they can take full sun.
Over a week or two, allow them to have more full sun a couple of hours a day.
Top tips for hardening off your seedlings
💦Be sure they are watered well as they will take up more water as they acclimate to their new environment.
❄️Remember, spring crops like it cool, not hot, so tend to like cool spring nights. If you have nighttime temperatures in the 40s, you could leave them outside in a protected area.
🌧💨Don’t leave your seedlings exposed to heavy winds or rains. Keep them either inside on those days, or keep them outside protected.
🦌If you have critters around who might want to eat your plants, harden them off where critters can’t get to them.
⌛If you work off-site full time. Check the weather before you leave in the morning to decide where you can safely leave your seedlings while you are gone.