Canning method
Combine beet mix, horseradish, vinegar, sugar and beets in large pot. Simmer for 10 minutes. Remove from heat. Add sliced onions, mix well. Pack beets into sterilized jars, leaving 1/2-inch headspace. Evenly divide hot pickling liquid among the packed jars, leaving 1/2-inch headspace.
Remove air bubbles and cap each jar as it is filled. If more liquid is needed for proper headspace, add a mix of 3 parts vinegar and 1 part water. Hot water bath for 20 minutes for pints and 30 minutes for quarts. Product is ready to eat in 24 hours.
Processing: As published by Mrs. Wages: "Hot water bath for 20 minutes" (boiling water bath canner) - 20 minutes.