Preserve the zucchini harvest bounty with this sweet and sour zucchini pickles recipe.
Combine the sliced zucchini and onions a large bowl.
Sprinkle salt over the zucchini and onions and toss to combine. Cover with crushed ice or ice cubes and water and let stand for 2 hours.
Drain the zucchini and onions and rinse well to remove the extra salt.
In a large pot, combine the vinegar, sugar, mustard seed, turmeric, celery seed, and peppercorns. Heat just to boiling.
Add drained zucchini and onion slices and return to boil. Reduce heat and simmer for 10 minutes.
Spread a kitchen towel on the counter. Use your jar lifter to remove the warm jars from canner. Drain and line up the jars on the towel.
Use the canning funnel and ladle to pack the zucchini and onions into the hot jars leaving 1/2-inch headspace.
Ladle the hot pickling liquid over the zucchini and onions maintaining 1/2 inch of headspace. Remove air bubbles with the bubble popper and wipe the rims.
Use the magnetic lid lifter to lift lids out of the warm water, center lid on the jar, and screw on band until it is fingertip tight.
Using jar lifter, place jars carefully into water bath canner on the jar rack leaving space in between them. Once jars are all in canner, adjust the water level so it is 2-inches over the tops of the jars. If adding water, use the hot water from your small pot.
Cover the canning pot and bring the water to a rolling boil over medium-high heat. Process pickles for 10 minutes. (Adjust for altitude if needed)
When processing time is complete, turn off heat and allow the canner to cool down for 5-minutes.
Spread a kitchen towel on the counter. Use a jar lifter to lift jars carefully from canner and place on the towel.
Allow the jars to cool for 12 to 24-hours. You should hear the satisfactory "ping" of the jar lids sealing.
After 12 to 24-hours, check to be sure jar lids have sealed by pushing on the center of the lid. The lid should not pop up. If the lid flexes up and down, it did not seal. Refrigerate jar and use up within a few days.
Remove the screw on bands and wash the jars. Label and date the jars. Store in a cool, dark location. Allow 4-5 weeks for the pickles to develop their flavor. Use within a year.