Transitioning tender seedlings to the outdoors isn’t always easy, and how to do it properly can sometimes be confusing. Here’s the best way to harden off plants quickly, easily and successfully!
“Harden off your plants.”
I was so baffled by these instructions when I first started gardening, almost 15 years ago now. Books and blogs alike will tell you, rather blithely, to “harden off” your indoor-sown seedlings and transplants before planting them in the garden.
But what the heck does “harden off” even mean? Why should you do it? And how do you do it properly?
Why Harden Off Your Plants?
It’s kind of a weird term, but to harden off your plants doesn’t mean to make them physically hard. It means to make them hardy. Impervious to the elements.
It is, at it’s most basic, simply preparing seedlings for life in the great outdoors.
Get more information on growing seeds here: 6 Tips to Grow Healthy Seedlings
Sown inside, seedlings are used to warm, even temperatures and diffused and constant light. The air is usually calm, and the water lukewarm. Outside, in contrast, can be harsh and mercurial. Rain, wind, hail, cold, heat, sun and shade can all affect a garden in the space of a single and normal spring day. A tender baby plant, grown and cared for indoors, will probably wilt and die if planted outside with no previous acclimation. They just don’t have the resistance necessary to deal with all the environmental changes and the shock of exposure.
The best way to help those seedlings you’ve labored over thrive outside, is to harden them off. Luckily, hardening off is a really easy process once you understand what to do.
How to Harden Off Seedlings
Some sources will advise you to go through really elaborate hardening off schedules. Like, an hour in dappled sunlight on a 50 degree day, gradually (over the course of a week) increasing time spent outside to the full day. Still in dappled sun. Then, and only then, can you start to harden off your plants in full sunlight for another week.
Um, ain’t nobody got time for that.
I agree that hardening off is important. But it can also be done so much more quickly and easily. Typically, I harden off my plants in five or six days. And I don’t spend any time at all worrying about dappled light.
Here’s my hardening off schedule:
- Day One: Place plants outside in the morning, and bring the plants back inside after a few hours, or earlier if they’re starting to wilt.
- Days Two-Three: Repeat the process, leaving them outside longer each day
- Days Four-Five: Assuming the weather is mild and no frosts are forecast, let the plants stay outside all night
- Day Six: Transplant them!
I would like to stress that I am in a very temperate zone 8, and my last frost date has already come and gone. If you are in a colder part of the world, you may very well choose to take more time to acclimate your seedlings to the outdoors. There is absolutely nothing wrong with that, and I urge you to always use your best judgement.
You might like: What to Sow and Grow in April
Tips to Make Hardening Off a Success
The one thing I have learned over the years is that hardening off is more of an art form than a science. There is no real “right ” way to do it; success has everything to do with your individual plant and weather conditions. That said, there are definitely some tips that will help your plants thrive outside, no matter where you are or how you do it!
- Try to start the process on an overcast or mild day
- Put your plants in a shady spot on the first day (or in dappled light even – I don’t judge!)
- Keep them somewhere safe from animals
- Avoid hot temperatures and bright sunlight
- Keep your plants watered
- Shelter your seedlings from strong winds if possible
- Shoot to transplant your seedlings on an overcast or mild day
- After you’ve planted, you may still need to provide protection (like cloches or row cover) if there is a spate of bad weather
Find your last frost date: USDA Hardiness Zones
Hardening off your plants is really not as intense or hard as you might think it is, but there’s no getting around it – it can be time consuming. However, this is not a step you want to skip! Your plants will thank you!
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