How to Can Tomatoes [without a pressure cooker]

Canning can be an intimidating process, but I am here to show you just how easy it is to can summer fresh tomatoes without a pressure cooker! It is a simple process of cooking the tomatoes on the stove, pouring them into sterilized wide-mouth mason jars, adding some salt, and then sealing them with a lid. Cooling on the counter overnight seals the jars removing the need for a pressure cooker. Anyone can do it and you'll enjoy summer tomatoes all year round for anywhere you would need tomatoes in a recipe.

mason jars full of tomatoes on a white background for How to Can Tomatoes

Growing up we had a MASSIVE garden. Full of okra, green beans, squash, eggplant, sunflowers, corn, zinnias, banana peppers, and tomatoes. There was nothing better than summer meals consisting of the fruits of our labor.

But I will admit, I wasn’t the biggest fan of tending to it or the work it required growing up - but I LOVED eating from it!

I especially loved walking downstairs to the basement in December and grabbing a can of green beans for dinner. There was truly nothing better than being able to have summer veggies all year round because of canning. We would have big canning days for green beans and tomatoes at the end of the summer. Sitting on the blanket snapping green beans with my grandmother, and helping my mom clean the jars for the tomatoes are some of my favorite memories!

Now that I am older, my soul craves some of those things from my childhood. And while I do have a pressure cooker, it still scares me and canning can require a bit of work - and I know that is the case for a lot of people. Like I don't want to blow up the house or injure myself. I know that is a bit dramatic but seriously! Those things are scary!

However, my mom had a very simple process for canning tomatoes that did not require a pressure cooker. At the end of the summer, I will buy a big box of canning tomatoes from our local CSA and spend the afternoon cooking them to have on hand throughout the winter months.

The process is super easy. You start by roughly chopping the tomatoes and cooking them in a big pot on the stove. Once they have cooked down, you add them to sterilized wide-mouth mason jars, add some salt, seal them with a fresh new lid, and let them cool in some towels on the counter overnight. The heat and slow cooling process is what naturally seals these jars - eliminating the need for a pressure cooker.

Let me walk you through step by step how to do it, and tips my mom taught me along the way!

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The 2 Ingredients Needed

10 pounds of tomatoes - so any variety will work. Using CSAs or farmers markets, farmers will sell big boxes of end-of-the-season canning tomatoes. These usually include irregular shapes or slightly imperfect, but that's ok! Any variety of tomatoes will work for this. And if they have a few imperfections, no biggies, you can cut those out. This is a perfect opportunity to buy end-of-season tomatoes for a great price.
5 teaspoons salt

Equipment Needed

Not a lot is required for this, just a couple of household items that you more than likely already have (or that are easy to get your hands on).

Large stock pot* - I have used this specific 20-quart taller stock pot as well as a smaller-sized Dutch oven. Any large pot that you would use for chilis or soups will work.
Wide mouth pint* or quart Mason jars
New wide mouth Mason jar lids and seals* or regular lids and seals*
Canning funnel*
Large deep soup spoon*
Towels - old towels or beach towels are perfect for this. But your regular bath towels will work too - you just want them to be large - no hand towels.

*All links are Amazon affiliate links*

PRO TIP - no matter which size jar you use (quart or pint) make sure it is the wide-mouth version. This makes it much easier to funnel the tomatoes in without getting anything on the seal.

ball mason jars stack on top of each other on the counter — I prefer using the pint-size jars. Since we are a smaller family, I like having smaller quantities of tomatoes instead of the larger quart size. Use what works for you and your family's needs.

Step-by-Step Process with Tips!

FIRST - Sanitize your jars. This is SUPER important and a step that cannot be missed. If your jars are not perfectly clean and without any grease or anything on the seal, it could effect the sealing process and not seal properly - causing the tomatoes to spoil, grow mold, and ruin. So make sure you prep your jars and seals very well! To sanitize, either run through the hottest cleaning cycle in your dishwasher with only the jars in them OR place them in a large pot of boiling water for 5 minutes fully submerged (use tongs to place the jars in and out of the boiling water). Place them on a drying rack or towel on the counter and face up to air dry completely before using. Wash and dry the new rings and seal them with hot soapy water, then let them airdry completelty. (note - I recommend using brand new seals for this process)

Wash and dry your tomatoes. Add a large stockpot to the stove over medium heat. Quarter or largely dice the tomatoes and add to the pot. Stir and bring to a shimmer. Place a lid on and let cook for 3-4 hours. The tomatoes will cook down during that time.
While the tomatoes are cooking, prep your jars. Place each mason jar in the dishwasher and run on a hot sanitizing cycle. Wash and dry the new rings and seal them with hot soapy water.
Once the tomatoes are finished and the jars are clean, place a canning funnel into the jar and slowly fill the jars with the cooked tomatoes right under the start of the seal - making sure not to get anything on the rim! Do not fill to the top. There needs to be room left in the jar. Continue filling until the tomatoes are all used. This will get you approximately 5-quart jars or 10-pint jars full.
Place ½ teaspoon of salt per PINT jar or 1 teaspoon salt per QUART in each jar. Again make sure not to get any salt or anything on the rim of the jar! But if you do, wipe the rims of the jars if any tomatoes or salt have gotten on the seal and rim with a clean dry paper towel.
Once the salt is in, place the new lids and seals on and close tightly.
Lay a beach towel (or a large towel) on the kitchen counter. Place each jar upside down on the towels and then place another towel on top. Leave wrapped in the towels on the counter overnight or for 24 hours to slowly cool.
Once they have cooled completely, double-check that they have completely sealed by placing your finger on top and checking for the top to not “pop”. Once sealed, store it in the pantry. Use in any recipe that calls for canned tomatoes.

tomatoes cooking in a large pot on the stove — Roughly quarter the tomatoes and cook over medium heat on the stove (with the lid on) for 3-4 hours. Stir occasionally.

washing mason jar lids in the sink — Sanitize and dry your jars, new seals, and lids with hot soapy water.

filling a mason jar with cooked tomatoes with a large funnel in the jar — Use a canning funnel to fill the jars to prevent anything from getting on the seal. Do not fill all the way to the top. Add in ½ teaspoon of salt per PINT jar or 1 teaspoon of salt per QUART - no need to stir.

canned tomatoes in mason jars turned upside down on towels on the counter — Place the seals and rims on tight. Place upside down on the counter on top of towels. Place towels over top of the jars as well. The slow cooling progress is what helps seal the jars without a pressure cooker. Using the big towels helps keep the heat in for longer allowing a slow cooling process over 24 hours.

MAJOR TIP - make sure the mason jars need are not cold when filling with the tomatoes. If you fill the jar that is cold with the hot tomatoes, it will break the glass on the jar. Make sure they are room temp or hot out after the santitzing cycle.

Making sure to keep the seal completely clean is super super important! If there is any salt, juice, or oil on the rim it will prevent the jar from sealing and will spoil the tomatoes and cause bacteria to grow - making them unusable.

If something gets on it, just wipe totally dry with a clean dry paper towel.

Once the cooling process has finished, press your finger in the center of the lid to see if there is any give. If there is not, your tomatoes are good to be put away and stored. If there is any give to it ("popping" at all), discard it immediately. There was likely something on the rim or seal of the jar making this jar unusable, unsafe to eat and bad.

How to Store

Keep your tomatoes in a cool dry place like your pantry. Just as you would store any canned food item you buy from the store.

These will last for 1-2 years. That is the beauty of canning! Being able to preserve food for an extended amount of time! If for some reason the seal is broken or compromised at any time during the canning process or after, discard it immediately. You do not want to risk getting sick from the bacteria that can grow if the seal is broken and contaminated. Use in any recipe that calls for canned tomatoes such as Baked Spaghetti and Ground Beef Casserole, Easy Dutch Oven Chicken Cacciatore, or Chili Con Carne.

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