Add lilac blossoms and huckleberries (or blueberries) to a saucepan and cover with 4 cups of water. Bring to a boil then simmer for 15 minutes over low heat. Turn the stove off and allow the flower infusion to steep for 4 to 8 hours.
Strain lilac tea using a soup bag or fine sieve. Add lilac tea, lemon juice, and pectin to a small saucepan. Simmer over low heat as you stir the pectin into the tea to dissolve. Bring to a rolling boil for one minute.
Add sugar and whisk to dissolve. Bring to a rolling boil for an additional two minutes. Skim foam off the surface and ladle hot jelly into sterilized hot jars. Leave ¼" headspace.
Wipe rims with a clean dishcloth or a damp paper towel and screw the bands on hand-tight.
Water Bath Canning Instructions
Add filled canning jars to the water bath canner. Make sure the water level is at least a few inches over the jars. Process the jelly jars in boiling water, based on the chart in this post.
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Notes
Many lilac jelly recipes only call for 15 minutes of steeping. I prefer to steep the lilac blossoms for a longer period to extract as much of the delicious lilac flavor as possible.
If you have a masher, use it to mash the berries to release their color.
I tried freezing my lilac blossoms to use them later in the year and found that they degraded too much. For this reason, I only recommend using fresh lilac blossoms.
Jelly needs to fully cool to set and may take up to 24 hours!
If your jelly does not set, be sure to check out the link in the body of the post for troubleshooting tips.
Sealed lilac jelly should last up to a year or more when stored in the pantry.
Do not reduce the amount of sugar suggested in the recipe, if you do, the jelly will not set.