Hardening Off Plants: Don’t Make These 7 Beginner Mistakes!

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Do you get exhausted hardening off plants? Hardening plants sure does feel like that pesky old cork in the way of sensational gardening experiences!

Let’s just get the plants in the ground already!

Well, slow down there! It’s vital to learn the correct way of hardening off plants or you’ll be likely to make some major gardening mistakes that could even risk your young plants’ lives!

I’ll make it nice and easy for you, sharing my own mistakes along the way so you won’t make the same ones!

Okay, let’s hurry up and harden off those plants!

(Of course if you haven’t started your seedlings yet, be sure to check out our post on the paper towel method! Or even if you have – don’t we always need more seedlings?!)

Hardening Off Plants for Planting Outside - Trays and Egg Cartons of Seedlings

Avoid These Gardening Mistakes When Hardening Off Plants

As an avid gardener, I’ll be the first to point out that hardening off plants should be shortened to…




Anyone with me?

I think most of us just want to get to it already! We want our wonderful plants in the ground so we can visit them every five minutes.

(You all do that too, right?)

In the excitement to hurry up and get planting, though, don’t leave plants at risk of these gardening mishaps! (It’s really not that hard, after all. I’m just an impatient gardener!)

1. Hardening Off Plants in Direct Sunlight Right Away

Did you know plants can get sunburn too? I sure didn’t!

Frustrated, I wondered why my green bean plants suddenly had leaves that were dry and papery thin.

Hardening Off Green Bean Plants with Sunburn on Leaves

I wondered why those papery leaves looked bleached!

So, I asked my mom. I asked my dad. (Both are gardeners.)

No one really knew why this was happening to my bean plants.

In a conversation with my sister, I discovered that plants DO, in fact, get sunburn.

If the sun is too strong, your plants’ leaves may scorch!

For this reason, you should absolutely set a schedule for hardening off your plants and stick to it.

2. Leaving Plants Outside Too Long

Likewise, even if the sun isn’t too strong from the get-go, you may find your plants suffer if you leave them out too long anyway.

Big differences exist between indoor light and outdoor light.

The harshness of the sun over time affects delicate young plants much differently than direct sown plants used to the bright sunlight.

Pro Gardening Tip: Set yourself a timer or an alarm each day so you don’t forget about your plants!

Hardening off Tomato Plants - Sunburn on Leaves

3. Forgetting to Bring Plants Inside at Night

You may get away with leaving your plants outside all day and overnight once you’ve hardened off the plants a bit.

However, young plants may face difficulties in withstanding the dramatic changes in daytime and nighttime temperatures.

And, it could be disastrous if you happen to get another frost or a big freeze overnight!

The long hours of sunlight may also be more than the unhardened plants can handle.

As mentioned above, something as simple as an alarm set on your phone can remind you to bring your plants back inside at the correct time.

4. Waiting Too Long to Start Hardening Off Plants

Sometimes life gets in the way – that’s what happened to us last year.

We ended up delaying our outdoor transplants due to going pretty swiftly from cold temps to 90 degrees! I also remember being distracted at the time, and that didn’t help.

Still, I got all the plants hardened off and planted in the ground safe and sound.

Check your area’s last expected frost date. Generally, here in Pennsylvania Zone 6b, we are safe on Mother’s Day weekend.

That wasn’t the case last year, and I think we ended up planting in June.

The plan’s to be much more organized when hardening off plants this year!

Waiting too long to Harden off Plants - Pumpkins and cucumber plants in pots

5. Forgetting to Water While Hardening Plants

Sure, bringing plants out and then back inside again is the important part.

But, if you forget to water them or to check each plant’s soil and how dry it is, you could be in trouble.

You’ll notice your plants beginning to wilt. When they look droopy, check the soil first and foremost!

If it’s dry, water the plants. If it’s not, you may want to give them a break from that day’s hardening off session.

6. Starting Seedlings Too Early to Harden Off

I know I get the gardening bug in late January, early February.

That being said, where I live, we can’t safely plant most things outside until mid-May.

If you start your seeds indoors without sufficient light sources, they become “leggy.” This means they are tall and spindly without much strength to support their weight.

If you start your seeds too early with light, you may find that they grow large so quickly that you need to continually “pot up” to a bigger container.

Potting up seedlings without hopes of planting outdoors anytime soon can be a lot of work.

Those bigger pots also obviously take up more space than your tiny cells inside the seed trays or egg cartons.

Whenever you decide to start your seeds, be sure that you have a plan in mind!

When you Harden Plants Long after starting seeds, the plants become leggy. Tray of seedlings

7. Getting Caught in a Downpour!

I can’t tell you how many times my seedlings were outside hardening off when a huge thunderstorm rolled through.

Luckily my daughters were great about helping me to rush everybody inside.

It may not have been a huge deal, but they were heavy rains and my plants lived on a table in the dining room, so mud wasn’t really a great option.

Hardening off Plants Outside on the deck

Final Thoughts: Hardening Off Plants

Hardening plants for outdoors is a rite of passage for being able to grow them. If you do it correctly, you should be able to get your plants outside in just a week or two.

Rush it and you might lose some plants.

Delay it and you’ll be up against ridiculous sun and temperatures.

Plan wisely and your plants will be happily growing outside in no time!

Give your plants the TLC they crave when hardening off so they will repay you in dividends all summer long.

You might also enjoy these 6 Hacks to Hardening Off Seedlings before Transplanting.

Do you have any good hardening off tips? Be sure to share any tips, thoughts, or questions in our comments below.

We’d also love if you share or save on social media to spread the word and protect all the sweet, innocent plants out there just waiting to be hardened off!

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