The Easy Way to Harden Off Seedlings

If you’ve started your own seeds indoors, you’re probably wondering if there’s an easy way to harden off seedlings.  Or maybe you’re wondering if it’s really necessary.  Or maybe you have no idea what it even means to harden off seedlings!

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Do I really have to harden off my seedlings?

First of all, yes, it’s definitely necessary to harden off your baby plants that started out indoors as seeds.  However, the good news is that it’s not hard.  Especially if you use this easy way to harden off seedlings.

What does it mean to harden off seedlings?

Hardening off is simply the process of slowly acclimating young plants from indoor conditions to outdoor conditions.  This usually takes place over the course of about a week, sometimes longer.

Why should we harden off seedlings?

If you think about it, outdoor conditions are very different from what a plant has experienced indoors.  Moving a plant from living completely indoors to living completely outdoors would come as quite a shock!  

By slowly exposing your baby seedlings to outdoor conditions, you’ll give them a greater chance at success.  They’ll be stronger and healthier because you didn’t just throw them outside and hope they’d survive.

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The easy way to harden off seedlings

I’m actually sharing two easy methods of hardening off seedlings.  One method is to use a cold frame, and the other is to carry your seedlings out and in every day.

Cold frame method

Personally, I love to create a temporary cold frame out of straw bales.  Bonus: later, you can use the straw as mulch in your garden.  

You’ll find more details here: How to Make a Straw Bale Cold Frame but the main idea is this…

1. Close the cold frame overnight and during extreme weather  to keep your seedlings protected.
2. Open the cold frame during the day or during calm weather to expose your seedlings to outdoor conditions.
3. Be sure to water your seedlings regularly!
4. After 7-10 days, your seedlings should be ready for planting.

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More cold frame options:

• How to Build a Cold Frame Out of Pallets
• DIY Cedar & Acrylic Cold Frame
• Portable Zipper Cold Frame
• Premium Polycarbonate Cold Frame

Manual carry method

This method works well for a modest amount of seedlings.  The upside is that you will not need a cold frame.  The potential downside is that it does take time to manually carry each tray of seedlings outside and back inside every day.  

Opting for this manual method also means you’ll need to be diligent not to forget about your seedlings!  Ask me how I know, ha ha.  

To keep things easy, I don’t worry about exact timing.  Some experts recommend taking your seedlings outside for an hour or two at first, and then increasing that time day by day.  Eventually you will leave the seedlings outside all day and all night.

Pro tip: it seems obvious, but the closer the hardening-off spot is to where the seedlings live inside, the easier this process will be.  If you have to carry every tray of seedlings out and around to the opposite side of the house every day, it will get old pretty fast!  

Here’s my easy process:

1. When it’s getting close planting time for a particular group of seedlings, I’ll start taking them outside during the day.  
2. I do try to avoid leaving them outside during extreme conditions like heavy rain, freezing temps, or hot midday sun.
3. For about 7-10 days, I take them outside every day, gradually leaving them out longer and longer.  
4. If possible, I like to leave them outside overnight for a night or two prior to planting.

And that’s it!  I really don’t worry about precise timing.

The main thing is to get them exposed to wind and sun and other outdoor conditions.  As long as you provide some measure of hardening off, your seedlings should do just fine.

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3 tips for successful planting

1. Choose a cloudy day followed by rain

If possible, keep an eye on the forecast and plant your hardened off seedlings on a cloudy day.  If rain is predicted, it’s even better!  

Planting on a cloudy day gives your plants a chance to settle in without being exposed to bright sun.  And of course a nice spring rain will water your plants in and save you the time of doing it yourself.

2. Plant later in the day

Planting young seedlings later in the day is another way to help them ease into their new life outdoors.  This gives them the chance to get settled in overnight, away from the sun’s hot glare.

3. Always water in

Give your newly planted seedlings a good watering, taking care to thoroughly saturate the soil around their roots.  This will help them get off to a great start.

And that’s the easy way to harden off seedlings!  What are you growing this year?  Did you start any seeds indoors?

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