The advantage of canning asparagus (which results in a softer texture than the freshly cooked vegetable) rather than freezing asparagus (which preserves the texture better) is that you can store the sealed jars at room temperature. That means if the power goes out, you needn't worry about whether or not your preserved asparagus are still good. It also saves room in your freezer.
Instead of traditional canning methods, a pressure canning technique is used here.
You will need to pressure can unpickled asparagus for food safety as it is a low-acid food. This creates a higher temperature needed to prevent the risk of botulism. For this process, you'll need quart-size canning jars, jar seal and rings, and a pressure canner.
- 14 pounds fresh asparagus
- Optional: 4 teaspoons salt
Gather the ingredients.
While you are cleaning the asparagus, bring 4 quarts water to a boil.
Wash the asparagus and snap off the tough ends. (Hold a spear at either end and bend it. It will break at exactly the point where the stalk changes from tough to tender.) Save the ends for making asparagus soup.
Once you've snapped all of the asparagus spears, make sure that none of them is longer than 6 inches, to allow space above the water line in the jar.
Lay a clean quart-size canning jar on its side. Slide in the asparagus spears with the wide base end of the asparagus toward the bottom of the jar. It is easier to get the spears to line up straight if you load the jar sideways like this, and that enables you to fit more asparagus into each jar. Keep adding spears until you can't squeeze any more in. The spears will shrink slightly during processing, and packing them tightly ensures they won't float up out of the canning liquid.
Add 1 teaspoon salt to each quart jar, if desired. Note that the salt is not a preserving factor here, but it does improve the taste of the final product.
Pour the boiling water into the jars to cover the asparagus. The asparagus spears should be fully immersed in the water, but there needs to be at least 1 inch of space between the surface of the liquid and the rims of the jars. Place the seals and rings on the jars.
Process the jars at 10 pounds pressure for 40 minutes (11 pounds with a dial gauge canner). If you want a shorter processing time, you can cut your asparagus spears shorter and pressure can them in pint jars instead of quart jars for just 30 minutes. Adjust the canning pressure if you live at a high altitude.
After 30 minutes, turn off the heat, and allow the pressure canner to cool and the pressure to drop to zero before opening it. Open the lid and lift the jars out of the water and let them cool on a wooden cutting board or a towel. You can then remove the rings if you like, or at least loosen them quite a bit, so they don't rust in place due to trapped moisture.
Once the jars are cool, test the lids to verify they are sealed. Just press in the center, gently, with your finger. If it pops up and down (often making a popping sound), it is not sealed. If you put the jar in the refrigerator right away, you can still use it for up to one week.
Label the jars and store away from direct light and heat.