How to harden off tomato plants is a question whose answer will enable your plants to prepare themselves when exposed to the conditions of an outdoor environment. If any plant is moved from its indoor space to the harsher situation of an outdoor garden, or something similar, chances are they will be unable to handle the conditions and die within a few days.

How To Harden off Tomato Plants

When you have hardened off the sensitive parts of your plants, it makes the adaptation process easier for them when they finally move into their new environment. If you think the hardening-off procedure might be challenging, the following sections have made every step easy for you to take care of your plants in the best way possible!

How Can I Harden off Tomato Plants? Most Safest Method

You can harden off tomato plants by choosing the right time of the season and the right temperature in the day to move. You need to shelter it from the cold and bring it back in. It will be ready for permanent moving by gradually spending more time outdoors.

1. Finding the Right Time for Hardening Off

The time when spring begins settling down to slightly warmer weather is when to harden off seedlings. This time is perfect since these plants are warm-season vegetables, and they cannot handle the cold weather since it could cause transplant shock and freeze them. It is crucial to note that you must not transplant the seedlings in the garden beds or any other container.

Finding the Right Time for Hardening Off

You should only do so when the temperature is above 15 C, which may also be measured as 60 Fahrenheit in other cases, in the mornings. The temperature could be around 10 C at night and no less than that.

It is essential to remember not to force the seedlings of the tomatoes in the garden because it could lead to damage. The vegetables that you can grow in the cool season are the ones such as broccoli and cabbage.

This is because these vegetables can get used to unpredictable and cold temperatures better than the other varieties. Tomatoes and peppers are more in the category of crops that love the heat. Due to this reason, it is best to start hardening them off in warm weather.

2. Taking Care of the Temperature

When you have hardened off your plants, and the temperature remains normal, you will have to put your plans of transplanting your plants for a few days later. After around seven days, you can put your tomato seedlings in your garden.

However, sometimes, there could be a problem, and you would have to wait a bit longer. It will allow the plant to harden off properly to keep you out of further trouble.

If not, you will have to go through a lot of trouble, firstly, growing the tomatoes from the seedlings. After that, you must harden off your plants and move them to a garden. This entire procedure will be useless since you will later lose all of your plants due to a frost that would be most likely to occur. It is best to harden off your plants only after studying the weather properly so that your plants do not die onwards.

3. Choosing the Right Day

Firstly, before you start, you have to choose the right day. On that day, the forecast should say that the temperature will be more than 15 C, or you can also say 60 F. After that, you have to take all of your cell packs, pots, and trays that contain the tomato seedling. Now, you have to put them outside of your house.

Choosing the Right Day

Make sure the soil is moist since this will show that the plant that will grow will also be moist. To prevent the potting mix from drying out too soon then, it is best to place your planter somewhere where it is shaded from the sunlight. You have to keep the tomato seedlings outside for some hours; after that, you can bring them back inside your home.

In case you are not at your home that day, you can leave the seedling lying out for the entire day. However, you must make sure that you locate your seedlings somewhere where they are being shaded at all times.

4. Moving the Plants

It is vital to move your plants out; however, you must make sure that the temperature is around 60 F. When you take them out, you have to find a shaded spot; once you do so, you can place your plant over there. It only matters if it is windy; it is all right if the wind is not harsh enough to blow away the plants.

If the wind is soft, it will not damage the plant. Instead, it will help the plant to grow well. After the plant has been in the garden for at least half of the day, it is necessary to bring it back indoors.

5. Allowing Sunlight

Taking the plant outdoors is crucial since it can receive the sunlight it needs there. Every morning, the plant should be taken out into the garden. When the sun is high, it is essential to cover up the plant while it is in the sunlight. You can also move the container to a shaded corner of the garden.

Taking the seedlings back inside your home before it gets evening is essential. If the plants are kept out longer, the temperature drops even below 50 F, and this can be pretty harmful to the plant. Another method you can use if you want to harden off the tomato plant is by putting up a small hoop tunnel. You can set it up using wire hoops and shade cloth.

6. Introducing More Sun

Now, you have to provide your plants with more sunlight. You have to take your plants outside in your garden in the early morning. After you take them out, you will have to leave them there for at least two to three hours.

Introducing More Sun

You must be careful in the afternoon and cover your plants from the intense heat. You can also place them where they get shade. It is essential to keep checking the soil of your plant. If the ground seems dry, then you have to water the plant. You must remember that if the seedlings get too much water, they could be damaged intensely.

At night, if the temperature exceeds 50 F, you can leave your plants outside in a sheltered place. Doing this will add a layer of row cover on the top of the seedlings. The row covers will provide the seedlings with extra protection further on.

7. Moving the Plant Out for Longer

Around the end of the spring season, you can start to move the plant out for a more extended period. You can keep your plants out in the sunlight for at least four to five hours in one day. Moreover, if the temperature is over 50 F at night, you can keep your plant out all night long.

Moving Them Permanently

However, it is crucial to cover the plants with a light cloth when night approaches. Doing this will keep your plants safe even if the temperature drops below 50. If you do not cover your plants, then it could cause your plants to freeze.

8. Gradually Increasing the Sunlight

As the days pass, you can slowly give the plants more and more time out in the sunlight. If the weather seems to get rainy or cloudy during the hardening process, adding in a few more days is best. You must remember that trying to harden off your plants on a cloudy day can be slightly tough to do. When it is sunny again, you have to ensure that the plants get an entire day of sunlight.

During the middle of the day, it is crucial to check on the plants. If the plants don’t look wrong, you can leave them be. You must also remember to check whether the soil is dry; if it is, you should water it right then. It is also all right to leave the plant out the whole night, but you must make sure that the temperature is suitable.

9. Moving Them Permanently

Usually, on the seventh day, you will have to take your plants out. If you do not know how to harden off your plants, then, after reading this article, you will indeed not have any trouble. Now, it is essential to keep in mind that if the temperature is warm and it does not drop during the day or night, you should transplant your seedlings.

When you transplant your plants, you must start transplanting them in any container or garden bed. It is best if you keep your row covers close to you; otherwise, it could also be troublesome. Later, you can also build a small hoop tunnel for your row covers.

The hoop tunnel will help to protect the row covers. When building your hoop tunnel, you must remember to use a very light-weighted cloth for it. After that, you must leave your plants under it for at least one or two weeks.

Doing this will help them to adjust and settle in. You must use aged manure, compost or any organic vegetable fertilizer before transplanting your plants. The last thing you must remember is to locate your plants under the full sun. This is quite essential for the plants’ growth.


Since we are concluding the article, it’d be the right time to revise everything you learned about hardening off your plants to save them from the sudden change to an outdoor environment. Check out the summarized points in the list below to remember everything you need to know about the process:

  • Select the right time of the season to harden off your tomato plants.
  • Not only that, on the day of moving, the temperature also needs to be ideal.
  • When moving the plants outdoors, you need to shelter them from the harsh weather and bring it back in, increasing the time spent outside gradually.
  • After adjusting to the temperature, the tomato plants will be hardened off sufficiently.

There must be more stress on the importance of hardening off your plants, especially the sensitive tomato ones, before you move them outside to your garden, as they will experience an abrupt change in the usual environment. Luckily, after studying our guide, you know the exact steps to prepare them for this change!

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