Hardening Off Your Plants, or They Will Die!

By now, you should have some seedlings that are ready to plant outside but don’t do it just yet because there’s a process called hardening your plants that you need to do.

Your seedlings have been cared for in a controlled environment, so they have not had to experience the sun’s harsh rays, blistering winds, or any other naturally occurring things that happen, so they are tender and weak.

What is hardening off plants?

Hardening off seedlings, also known as adjustment period, is a process that gradually exposes them to the elements to thicken the cuticle on the leaves, losing less water and minimize transplant shock.

Transplant shock will generally cause your plants to die, or be stunted and slow the growth.

When do you harden off your plants?

You want to harden off your plants at least 1 week prior to being planted outdoors. 

This process to harden off your plants is not difficult to do, but many people have lost beautiful starts because they fail to do this part.

Hence, the reason we need to harden off your seedlings before planting them outside. 

What You'll Need

Since this process is easy to do, I’m going to make give you the simplest way of doing this, which does not require anything additional to purchase. However, it will be a little laborious.

You will need a place that is protected from animals and foot traffic. 

The first time I hardened off plants, I would take the seedlings in their pots on a cookie sheet outside and put them on the ground.

Yep, that’s it!

You don’t need any fancy racks or special transition houses, just a cookie sheet or large flat carrying apparatus. 

I gradually added a rack, which makes it easy to roll in and out of the garage but I didn’t start this way and you don’t need to either.

Instructions for Hardening Off Your Seedlings

You can harden off plants in a week and at most two weeks.

Day 1 - 1 hrs

Use morning sun to harden plants.

Hardening process begins so take your seedlings out in the morning before 10 am or in the shade if it’s later than 10 am on a day that outdoor conditions are above 45 degrees (remember they are fragile)

The first time you bring your seedlings outside, you want to do it in the morning, when there’s no strong winds and the sun’s rays are not too intense, so only take them out for 1 hour.

After 1 hr, bring your tender plants back into their warm safe growing environment that they are used to.

Day 2 - 2 hrs

Today take your seedlings out in the morning again and leave them outside for a couple of hours, 2 hours, to be exact still protecting them for the harsh rays of the sun.

After 2 hrs, bring them back to their safe haven.

Day 3 - 4 hrs

This is the day they get to experience a little bit of the harsh reality of life outdoors. You want to take them out in the morning about 9am and leave them outside for 4 hours and experience a little bit of the sun’s intensity and get direct sunlight. 

After the four hours bring them back into their safe haven or at this point you can start leaving them outside a little longer as long as they are shaded.

Day 4 - 6 hrs

Your little seedlings are growing up and started to put on their adult pants (build their cuticle on their leaves) and you are going take them outside at 9-10am and leave them outside for 6 hours (at this point, I don’t worry as much as the first couple of days.)

The seedlings need the direct sunlight so allow them to experience more and more of the sun’s rays and also the other elements, some wind, etc. (I don’t worry about the wind from day 2 on unless it’s really windy and is blowing stuff around)

You will still want to bring your seedlings in after 6 hours, they’re part time workers right now.

Day 5 - 8 to 10 hrs

Soon my little seedlings, soon.

This is the day your seedlings act like adults and go to work for full time. You will take them out in the morning and leave them outside all day and bring them in only if it gets really windy, stormy or outdoor temperatures drop below 45 degrees.

Day 6 - Let Them Go

At this point, you really should leave them outside all night as long as the outdoor temperatures stay above 45 degrees.

In case you’re a little nervous because your little ones are growing up so fast and you’re not quite certain you’re ready to let them go, bring them in at dusk and sing them their last lullaby because tomorrow is the big day.

Day 7 - Plant

The day of reckoning has come and it’s time for your seedlings to leave their nest and go on their own.

Today is the day to plant them outside in their forever home but not all parenting duties are done, you will need to watch temperatures and make sure they don’t dip below 40 degrees.

If temperatures do dip below 40 degrees, you will need to protect them with a blanket, tarp or some other method to shield them from the cold.

They will be able to handle a lot cooler nights but below 40 degrees is almost too cold.

Seedling Warnings

Here’s a few warnings when it comes to the hardening off process.

1. Do not put your tender seedlings out on a windy days.

2. Bring them in if temperatures drop below 45 degrees.

3. Don’t forget to water them, they still need your loving embrace.

4. Protect them from the sun’s harshest rays for the first several days.

5. Check the weather for the next 10 days and determine if you can plant them on day 7 or not, sometimes there’s a last freeze the comes through and it’s easier to protect them inside then sheets, blankets and tarps outside.

Go to Weather.com to get the weather forecast for your area.

Now your beauties are in the ground, and you shouldn’t have any problems except for pests, sudden drops in temperatures, and animals, but they have been hardened off and prepared for the great outdoors, and that’s the process you need to go through to prepare them to leave the nest so they can have the best start in life.

Do you need to harden off all plants?

The short answer is, No! 

You don’t really need to but there are consequences if you don’t. I’ve had success when I haven’t hardened off my plants as well as when I have but I have greater success when hardening off my plants, so just do it.

I’ve lost many tomatoes, beans, squash, lettuce, and broccoli plants because I didn’t harden them off. I hope you learn from my mistakes.

If you don’t go through this process of hardening off your plants, they may experience shock and wither up and die. I can’t say it’s definite, but I’ve seen many people lose their precious little ones because they were not prepared. I don’t want that to happen to you.

I’ve said this before and I’ll say it one more time, while in the hardening process, do NOT take or leave them outside if it’s below 45 degrees; these temperatures will kill many plants because they are in pots, not the ground.

The Get to the Roots Difference for Hardening Plants

There are some gardeners that say you shouldn’t expose your seedlings to the sun on day one. I disagree as long as the sun exposure is the early morning sun, by doing this I’ve found that I can speed up the hardening process.

If you’re nervous, do a few plants my way and do some that take two weeks for the hardening process to happen and let me know your thoughts?

Did I miss anything?

As I write articles my mind goes all over the place of different things and sometime I miss something, or I don’t answer a question you may have so contact me if missed something or you have a question.

Contact Tony Rhoton
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