how to harden off plants

How To Harden Off Plants? – Seven Days To Go

Your indoor seedlings are ready for the outdoor environment. However, they must be hard and sturdy enough to withstand the changes in their living conditions. 

So, how to harden off plants? We will help you figure it out with the step-by-step instructions below. Let’s dig into the details! 

how to harden off indoor plants
how to harden off indoor plants

How To Harden Off Plants?

Hardening of the seedlings is a crucial stage to take before bringing them outdoors. This process entails training the newly sprouted seedlings to familiarize themselves with the outdoor environment. 

Indoor-grown plants are vulnerable to heat and transplant shock when adequately hardened off. Their leaves will curl under or fall off as a result. And these problems happen to vegetables, flowers, and herbs.  

So, you need to harden off your plants. Here is how to do it properly.  

Step 1: Determine when to harden

It’s necessary to start answer the question how to harden off plants by hardening your pants one to two weeks before setting them out in your garden.  

In spring, your seedlings can move outdoors after the last frost. Nevertheless, if you have cold-hardy species, wait about two to four weeks before the last frost to relocate them to your garden.

how long to harden off plants
how long to harden off plants

Step 2: Plan the sun exposure schedule

How to harden off plants process usually takes seven days. Yet, you should extend the process to two weeks if the weather drops suddenly.

Often, a seven-day hardening is sufficient. You can check this schedule for how to harden off plants and apply it to your plants. 

  Intensity of sunlight     Time of exposure  
  Day 1    Partial sun   2-3 hours 
  Day 2    Partial to full sun   3 hours 
  Day 3    Full sun   4 hours
  Day 4    Full sun   5-6 hours
  Day 5    Full sun   All day 
  Day 6    Completely outside   All day and night 
  Day 7    Completely outside   All day and night 



  • Day 1

Your garden should be wind-free and above 60 degrees. If possible, place your seedlings under the shade of a big tree. 

Since the plants are just starting to adapt to the new environment, do not expose them to the sun for more than three hours. Also, check the moisture carefully, or the plants will dry out. 

  • Day 2

Place the seedlings outdoors under partial to full sun for three hours. They would also benefit from a gentle wind.

  • Day 3

Like the previous day, try to give the seedlings a mild wind and watch out that they don’t stay dry and droopy for an extended period of how to harden off plants.  

  • Day 4

Allow your plants to contact more sunlight. You can bring them outside earlier for them to experience a cooler temperature. 

At the end of the day, bring your plants back inside. Remember to check if the soil is still moist. 

  • Day 5

Leave your plants out in the light and wind all day. If it’s a hot day, give them some water to keep them moist. 

Additionally, keep an eye out for garden visitors, like birds or squirrels. These animals may nibble your plants if they taste good. 

  • Day 6

Now, your lovely seedlings are ready for the first overnight. You can leave them the whole day in your garden if the weather isn’t freezing. 

The most annoying problems here are voles, mice, and pests. They may kill your plants due to their love for new plants. 

  • Day 7

Your seedlings have completed hardening off and can thrive in the garden, whether in the ground or a bigger outdoor container.

To allow seedlings time to adapt to a new environment, perform the transplant on an overcast day. However, at this point of how to harden off plants, they should be able to withstand direct sunlight, spring showers, and mild winds.

How Warm Is It To Harden Off Plants?

The plants generally need a temperature range of 40°F to 65°F. Yet, the answer varies depending on the species you cultivate. 

  • 40°F for hardy plants, such as rhubarb, broccoli, kohlrabi, Brussels sprouts, leeks, cabbage, onions, parsley, etc. 
  • 45°F for half-hardy plants, such as beet, celery, lettuce, Chinese cabbage, endive, etc.
  • 50°F to 65°F for tender plants, such as pumpkin, sweet corn, tomatoes, peppers, cucumber, etc.

Extra Tips For Hardening Off Success

how to harden off tomato plants
how to harden off tomato plants

In addition to the guidelines for how to harden off plants we have shared, there are some other things to consider. For example:

  • Do not place your seedlings on the ground where birds or slugs can knock. Also, avoid too bright sunlight. 
  • If you have the room, grow some more plants. Beginners should bear in mind this tip as some of their first seedlings will fail to adapt to the outdoor condition. 
  • Bought plants may need hardening off, especially if you keep them in sheltered circumstances.
  • Don’t rush the procedure. Although it takes time, hardening off will result in sturdier and more productive seedlings.

How To Transplant Seedlings To The Garden?

When the hardening-off process completes, you can transplant the seedlings to your garden. The detailed instructions for how to harden off plants are as follows:

  • Eliminate all weeds from your vegetable beds before introducing fertilizer and compost. 
  • Before transplanting, give your seedlings plenty of water. It will reduce the impact of soil overflow and minimize transplant shock.
  • Dig a hole for each seedling using a shovel. The hole should be about the same depth but slightly wider than the container.
  • Remove the seedlings from their containers by pressing the sides and flipping them. Meanwhile, hold your palms over the soil. Therefore, the plant’s base is between your index and middle fingers.
  • Pull the dirt in from the sides of the hole, carefully fill it in, and delicately center the seedling.
  • Give a light watering at the plant’s root. 
  • When the seedlings have established, wait a little while before watering them again.
  • Mulch the soil beds to control weeds and preserve soil moisture after the seedlings have settled themselves.
  • To prevent the mulch from suffocating the seedlings, leave it a few inches away from their stems.
how to harden off pepper plants
how to harden off pepper plants


To answer the question “How to harden off plants?“, you need to expose them to the sun gradually. Depending on your local weather, the process may take one week or longer. 

The temperature and moisture are important in every stage of the process. Ensure to study your plants’ characteristics for a successful project of how to harden off plants

Hopefully, you will find this guide helpful. For any further information, please feel free to ask. Thank you for stopping by! 


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