Preserving the harvest is a timeless tradition that allows you to enjoy the vibrant flavors of summer long after the frost has settled on the ground. When it comes to leafy greens, spinach is a nutritional powerhouse, but its high water content makes it prone to spoiling quickly in the refrigerator. Learning how to make canned spinach—specifically through pressure canning—is the most effective way to lock in those vitamins and minerals for year-round use.
Whether you are an avid gardener with an overwhelming surplus of “Bloomsdale” or simply a savvy shopper who found a great deal at the local farmers’ market, canning spinach ensures that a healthy side dish is always just a pop of a lid away.
The Essential Science of Canning Leafy Greens
Before diving into the jars and ladles, it is crucial to understand the “why” behind the process. Spinach is a low-acid vegetable. In the world of food preservation, low-acid foods are those with a pH level higher than 4.6. This is a critical distinction because the bacteria that causes botulism, Clostridium botulinum, thrives in low-acid, oxygen-free environments—exactly the kind of environment found inside a sealed canning jar.
Unlike high-acid fruits or pickled vegetables, which can be safely processed in a boiling water bath, spinach requires the intense heat of a pressure canner. To effectively destroy botulism spores, the internal temperature of the food must reach 240°F. This temperature can only be achieved under pressure.
Equipment You Will Need
Preparation is the secret to a stress-free canning session. Ensure you have the following items cleaned and ready to go:
- Pressure Canner: Do not attempt this with a standard stockpot or a water bath canner. A weighted-gauge or dial-gauge pressure canner is mandatory.
- Canning Jars: Pint or quart-sized Mason jars are standard. Check for any nicks or cracks in the glass.
- Lids and Bands: Use new flat lids for every batch to ensure a proper seal; bands can be reused if they aren’t rusted.
- Large Stockpot: For blanching the spinach before it goes into the jars.
- Canning Tools: A jar lifter, a bubble remover (or a plastic spatula), and a wide-mouth funnel.
- Spinach: Fresh, crisp leaves are the best. Avoid any that are yellowed or slimy.
Step 1: Selecting and Cleaning Your Spinach
The quality of your canned product is only as good as the quality of your fresh produce. When selecting spinach, look for deep green leaves with no signs of wilting.
Cleaning is the most labor-intensive part of the process. Spinach is grown in sandy or silty soil, and those grains of grit love to hide in the crinkles of the leaves.
- Fill a clean sink or a very large basin with cold water.
- Submerge the spinach and swish it around vigorously.
- Lift the spinach out of the water (leaving the dirt to settle at the bottom) and drain the basin.
- Repeat this process at least three times, or until no sediment remains at the bottom of the basin.
- Remove any thick, tough stems, as these can become woody and unappealing after the high-heat processing.
Step 2: Blanching for Quality
You cannot pack raw spinach directly into jars. If you do, the air trapped in the leaves will expand during processing, potentially causing the jars to boil over or preventing a proper seal. Furthermore, the volume of spinach reduces significantly when heated. Blanching “shrinks” the greens so you can fit a reasonable amount into each jar.
Place the cleaned spinach into a large stockpot with a small amount of water or steam it until it is thoroughly wilted. This usually takes about 3 to 5 minutes. You want the leaves to be limp but not turned into a complete puree.
Step 3: Packing the Jars
Once your spinach is wilted, it is time to fill the jars.
- Preheat Jars: Keep your jars warm in a pot of hot water to prevent the glass from cracking when you add the hot spinach and liquid.
- Fill: Use your funnel to pack the hot spinach loosely into the jars. Do not cram it in too tightly; the heat needs to circulate between the leaves to process safely.
- Add Liquid: Cover the spinach with fresh boiling water or the hot cooking liquid. Leave exactly 1 inch of headspace at the top of the jar.
- Seasoning: If desired, you can add 1/2 teaspoon of canning salt to pint jars or 1 teaspoon to quart jars. Salt is purely for flavor and does not affect the safety of the preservation.
- Remove Bubbles: Run your bubble remover tool around the inside edge of the jar to release any trapped air. Adjust the liquid level if necessary to maintain that 1 inch of headspace.
- Seal: Wipe the rim of the jar with a clean, damp cloth to remove any residue. Center the lid and screw the band down until it is fingertip-tight.
Step 4: The Pressure Canning Process
Place your filled jars on the rack inside the pressure canner. Add the amount of water recommended by your canner’s manufacturer (usually 2 to 3 inches).
- Venting: Place the lid on the canner and turn the heat to high. Allow steam to escape from the vent pipe for a full 10 minutes before placing the weight or closing the petcock. This ensures all air is removed from the canner.
- Reaching Pressure: Adjust the heat until the gauge reaches the required pressure. This depends on your altitude. For most regions under 1,000 feet, you will use 10 pounds of pressure for a weighted gauge or 11 pounds for a dial gauge. If you live at a higher altitude, check local extension guidelines to increase the pressure accordingly.
- Processing Time: Once the correct pressure is reached, start your timer.
- Pints: 70 minutes.
- Quarts: 90 minutes.
- Cooling Down: When the time is up, turn off the heat. Do not touch the weight or the lid. Let the pressure drop to zero naturally. This can take 30 to 45 minutes. Opening the canner too early can cause “siphoning,” where the liquid is sucked out of the jars.
Step 5: Post-Processing Care
Once the pressure is gone, carefully remove the lid. Let the jars sit inside the canner for another 10 minutes to acclimate to the room temperature. Use your jar lifter to move them to a wooden board or a towel-lined counter.
Leave the jars undisturbed for 12 to 24 hours. You will likely hear the satisfying “ping” of the lids sealing. After they have cooled completely, check the seals by pressing the center of the lid. If it doesn’t flex, the jar is sealed. Remove the bands, wash the jars to remove any mineral deposits, and store them in a cool, dark place.
How to Use Your Canned Spinach
Canned spinach has a softer texture than fresh or frozen, which makes it perfect for specific types of cooking. It is an excellent addition to:
- Soups and Stews: Stir it into a minestrone or a creamy potato soup during the last few minutes of cooking.
- Dips: Drain the spinach thoroughly and mix it with artichokes, cream cheese, and garlic for a classic appetizer.
- Casseroles: Layer it in lasagna or mix it into a breakfast strata.
- Side Dishes: Sauté it briefly with some olive oil, garlic, and a splash of vinegar or lemon juice.
Frequently Asked Questions
Can I use a water bath canner for spinach if I add extra vinegar?
No. Spinach is a low-acid vegetable, and adding a small amount of vinegar does not raise the acidity enough to make it safe for a water bath. To safely preserve spinach without a pressure canner, you would need to fully pickle it in a strong brine, which results in a very different flavor profile and texture.
Why did my spinach turn a dark olive color after canning?
The high heat of the pressure canning process breaks down the chlorophyll in the leaves, which causes the vibrant bright green of fresh spinach to shift toward a darker olive drab. This is perfectly normal and does not mean the spinach is bad or has lost its nutritional value. Commercial canned spinach has the same appearance.
Is it necessary to wash the spinach so many times?
Yes. Spinach is notorious for holding onto sand and grit. Because you are concentrating the spinach through blanching and then sealing it in a jar, any remaining grit will be very noticeable and unpleasant when you eventually eat it. The “three-rinse rule” is a standard safety measure for both cleanliness and food quality.
Can I can spinach with butter or cream?
You should never add fats, oils, or dairy products like butter or cream when pressure canning spinach at home. Fats can coat bacteria and protect them from the heat, and dairy requires industrial-grade processing to be shelf-stable. Always can your spinach in water or its own juice, and add your butter or cream when you are ready to heat and serve it.
How long does home-canned spinach last?
For the best quality and nutritional value, it is recommended to use home-canned spinach within 12 to 18 months. While the food may remain safe to eat for longer if the seal remains intact, the texture will soften further and the vitamin content will gradually decrease over time. Always store your jars in a cool, dark, and dry environment to maximize their shelf life.