Gardening | Seed Starting

Hardening off Tomatoes (12 Easy Tips for Seedlings)

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Starting tomato seedlings indoors gives your plants a healthy head start! Hardening off tomatoes before you transplant them outside will give your tiny toms the best chance to survive and thrive.

Do you love your tomato plants?

Do you want them to thrive all summer and fall long?

By following proper tomato care tips, your beefsteak, Roma, and cherry tomato plants can be healthy, heavy producers.

Your counters may soon be full with tomatoes!

As long as you succeed in hardening off tomato seedlings before transplanting them outside, you should enjoy healthy plants that truly take off once it gets warm enough outside.

Let’s talk about hardening off tomato plants so you can get stared!

Hardening off Tomato Plants - Sunburn on Leaves
This baby tomato plant got a touch of sunburn during the hardening off process.

How to: Hardening Tomato Plants

Hardening off tomatoes is much easier than it sounds! This process protects tomato seedlings from wind, sun, and temperature shock.

Begin acclimating tomato plants to the outside world by gradually exposing them to the outdoor climate a little bit at a time.

Check out our article on Hardening Off Seedlings before Transplanting (6 Easy Hacks) for a helpful foundation on how to do this.

In the simplest terms, try these steps for hardening tomatoes:

  1. Bring your tomato seedlings to a shady area for one hour on the first day. A sheltered garden or space near a wall of the house or garage works well.
  2. Repeat the process on day 2, increasing the time to an hour and a half or two hours.
  3. Add an hour each day to get the tomatoes used to the sun and outside climate.
  4. Gradually put your tomato seedlings in the sun for a little bit at a time.
  5. Increase the duration in the sun each day by a little bit.
  6. By 10 days, your tomatoes may be in the sun as many as 10 hours a day!
  7. If the temperature remains above 50 degrees, consider leaving them out overnight before transplanting to ensure they are fully hardened off.
  8. Make sure your plants are able to withstand the sun all day before transplanting tomato seedlings in their permanent homes.

Important Tips for Hardening Off Tomatoes (Seedlings)

  • Avoid putting the tomato seedlings in direct sun the first few days.
  • You might also avoid the hottest or brightest part of the day for the first few days of hardening off.
  • Watch for wilting. If you notice your young tomato seedlings wilting, give them some water or bring them back inside.
  • Choose a day that’s not windy to start hardening off tomato seedlings. A little breeze can strengthen stems but extreme winds can snap them or injure the plants.
  • Give your young tomato plants some shelter – I first harden tomato seedlings off near shrubs and an exterior wall to give a little shelter from the wind.
  • Watch the weather. Try to maintain a minimum of 50 degrees. If you notice a thunderstorm in the forecast with possible hail or tons of soaking rains, you might want to reschedule or skip hardening off that day.

In 2020, we had a late freeze around Mother’s Day, when we are generally safe to plant outdoors. For this reason and others, I delayed hardening off my plants and getting them outside.

Hardening off Seedlings Tomatoes with a Wagon, Little Girl and Border Collie Pulling it

I ended up finally planting everything outside about a month later, in JUNE!! This is ridiculous for Zone 6, mind you, as our growing season just isn’t long enough.

Big mistake on my part, but we still had a fun growing season.

By the way, with this in mind, you might also enjoy my other post, Hardening Off Plants: Don’t Make These 7 Beginner Mistakes!

Hardening Off Tomato Seedlings for Transplant without Shock

When it comes time to move your seedlings outside to their new adventures in the great big world, the last thing you want is to accidentally kill them.

Be absolutely sure not to leave them outside in temperatures under 50 degrees!

I’m being very serious about this as I don’t care to be an accessory to seedling murder!

What Are the Signs of Transplant Shock?

Common signs of plants suffering from transplant shock may include:

  • Wilting
  • Yellowed leaves
  • Curling leaves or rolling leaves
  • Branches dying back
  • Other signs of stress on the plant

Try these tips for hardening off tomato seedlings for transplant without worrying about transplant shock:

  • Take your time when hardening off tomatoes. Don’t rush it or you’ll risk losing seedlings to extreme temperatures, sun, or wind.
  • Water the plant at the base. Avoid watering the entire plant, wetting the foliage, and so forth. Plants suffer less stress when watered by the roots.
  • Do not transplant tomatoes in direct sun. Choose a cloudy day or a less bright part of the day to transplant.
  • Water after transplanting. Be sure you set your baby plants up for success.
  • Do not transplant your seedlings until after the danger of frost has passed. Move them to the ground or in their permanent homes when it’s safe to plant outside in your zone. Remember, low temperatures could harm or kill your tomato seedlings.
  • When transplanting, avoid disturbing the roots if possible. If the root ball is thickly wound, try to resist the urge to pull it apart or otherwise bother it.

Final Thoughts: Hardening Off Tomatoes

Tomatoes tend to be some of the most rewarding plants to grow in the garden. Have fun with your gardening adventures and don’t stress out about hardening off your plants.

The truth is, if you forget a day or your schedule is a bit short or a bit long, your plants (most times) will forgive you.

Enjoying a Glass of Wine while Hardening off Seedlings on the Deck in the Sun

Just be sure to watch them for cues of stress and how they’re doing.

If you’re still a bit nervous about hardening off your tomatoes, only harden some of them. Keep a few plants indoors under lights and plan to start them outside a bit later than the others!

Do your best to go with the flow and avoid adding pressure to yourself. Gardening is meant to be relaxing!

What are your favorite tips on hardening off tomato seedlings? Please share your best tips and tricks in our comments below.

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