Hand-Grow Plants Faster by Hardening Off Seedlings in 2 Weeks or Less

You know, for something that sounds akin to college hazing, hardening off seedlings is not that intense.

Let’s start hardening off seedlings, it can’t be that hard. Just set them outside, and then you’re done!

So you do exactly that, and you are face to face with dead seedlings, sunburned out of recognition. An entire month of labor, lost.

If I just set your worst gardening fears, I apologize.

Hardening off seedlings is an essential part of starting plants from seed indoors. It’s easy to get the hang of, and you can get the entire process [yes, process] done in less than 2 weeks.

I’ve successfully hardened off seedlings that helped me grow these beautiful tomatoes from seed last year! And I didn’t do anything more than follow a simple, time-tested formula.

If you want healthy, beautiful plants outside in less than two weeks, here is your updated guide on hardening off seedlings!

What’s Hardening Off Seeds?

Hardening off seedlings sounds like an army boot camp, but it’s a different type of training.

It’s training and preparing your plant babies for the real world.

Inside your cozy home, your plants are sheltered and protected from the scorching sun, nibbling animals, wind, and more. Even if your grow light for growing seedlings is the best around!

The process of hardening off seedlings includes gradually exposing your seedlings to the environment bit by bit until they can be left on their own.

This happened over the course of only 2 days!

Why Should I Start Hardening Off My Seedlings?

Because what happened to my tomatoes will happen to your tiny plants if you don’t.

I was once like you, and I just plopped my seedlings outside on my porch and left them to bask in the sun.

But every day, I found my seedlings even weaker and spindly when I looked at them. Then I brought them inside and accessed the damage.

The damage from the sun almost ruined my lettuce, tomato, and pepper plants.

Thankfully, they recovered, but I sure learned my lesson and didn’t skimp on hardening off my seedlings. Like how you shouldn’t skimp on high-quality potting soil.

If you wouldn’t leave a newborn baby out of the house without any protection, why would you do the same to your plants?

Of course, some plants don’t need to be started indoors at all, like radishes.

When Should I Start Hardening Off Seedlings?

Now this answer is going to be quite unsatisfying, but… 

It depends. But definitely when your seedlings are a couple inches tall.

A good guideline for hardening off seedlings is after the last frost date. Seed packets will also tell you when to transplant your seedlings outside too!

For cool-season plants like lettuce and kale, wait until nighttime temperatures are in the low 50’s. When transplanting warm season plants like tomatoes, wait until nighttime temperatures are in the high 50’s.

For cold-hardy plants, you can transplant them before the frost date.

How to Start Hardening Off Your Seedlings in Less Than 2 Weeks

Before You Bring Them Outside: Harden Off Your Seedlings Indoors

Yep, you heard me. Hardening off seedlings starts before you even bring the plants outside.

Every day, you should be brushing your hands over your seedlings for a couple minutes to help them get used to the wind. When you do this, it tells the seedlings to start growing more roots to support them and keep them from getting spindly.

Week 1: Bring Out Your Seedlings into The Shade

Gardening tip: I highly recommend you on keeping a timer on your phone so you don’t accidentally leave your plants out and burn them!

For the first week, you should be bringing their seedlings out into the shade starting for an hour. Every day, you should increase the time by 2 hours.

So for the first day, leave them out for one hour. The second day, 3 hours. The third, 5 hours, and so on.

When the timer is up, bring your seedlings back inside.

By the end of the week, you should be able to keep your seedlings in the shade for 13 hours, or overnight.

Gardening Tip: For easy transport inside and outside, keep all of your seedlings in a tray!

My wonderful marigolds soaking in the sun!

Week 2: Harden Off Your Seedlings in Direct Sun

Now that your seedlings are comfortable enough to stay in the shade all day, it’s time to turn it up a notch! This week, you should be focusing on hardening off your seedlings in direct light. [See the definition of direct light here]

By now, you should be leaving your seedlings overnight in a place that always gets shade.

Start by leaving your seedlings out for an hour in direct sun, then move them back to the indirect sun. Every day, increase the amount of time your plants are in the sun by 2 hours. So the second day, 3 hours in direct sun, the third, 5 hours in direct sun, you get the pattern.

By the end of the week, you can consider your seedlings hardened off! Congrats! You can now move your plants to their permanent locations.

After leaving my cucamelons out for a couple days, most of the seedlings withered away from the sun.


Did you accidentally leave your seedlings out? Was increasing the time by 2 hours too much?

Okay, first of all, deep breath in, deep breath out. It’s going to be okay. The world is not ending.

If your seedlings seem to be weaker and have a blanched look to them, they’re sunburnt.

I’ve burnt a fair share of seedlings, but that doesn’t mean that they are long gone! Of course, if they’re burnt to a crisp or so severely damaged that you can’t recognize them anymore, it’s time to start some new seeds.

All you need to do is move them back indoors or in the shade for the rest of the day.

If you accidentally left your seedlings outside for too long, then keep a timer on your phone to remind yourself.

If increasing the time by 2 hours seems to bring stress to your plant babies, reduce it to an hour.

Keep following the previous steps, and your plants will recover! My tomato plants were sunburnt for 3 days before I noticed, but they still grew strong and healthy!
I wish you the best of luck on your journey. Hopefully, my mistakes will prevent any from coming your way.

So What, Sarika?

So what, is that you should start hardening your plants off, if the weather permits.

If it’s too cold to grow anything outside, don’t you worry! Currently, I am growing 5 winter vegetables for a winter gardening challenge with nothing but some dirt, a growlight, and a little bit of hope.

If you want to learn about more plants to grow and get to know me personally, subscribe to my Plant of the Month! I share gardening experiences, and teach you about a new plant every month! You can always unsubscribe!

Before you go, don’t forget to snag your gardening dictionary! I collected and defined more the 100 of the most common gardening terms you’ll come across. So that next time you encounter a gardening word, you’re not scratching your head and saying, “Huh?”.

And that’s all for now. Happy Gardening, till we meet again.

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My name is Sarika, and I am the founder of “The Blossoming Gardener”! Let me tell you a little bit about myself…Read more

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