Begin by gathering your dandelion blossoms. Choose flowers that are fully open and free from pesticides. I usually pick them into a quart jar, which gives me just the right amount for the next step.
Carefully remove the petals from the flowers, leaving behind any green parts or stems. The easiest way I’ve found to do this is by breaking the flower half (from top to bottom) and then pulling the petals out of each side. Once it’s halved, the petals come out easily. From 1 quart of whole blossoms, you should have 2 cups of dandelion petals.
Place the dandelion petals into a heatproof jar or bowl, and pour 4 cups of boiling water over them. Let them steep for about 15 to 20 minutes, until the water turns a vibrant yellow. After steeping, strain out the petals, reserving the yellow liquid.
If canning, now’s the time to preheat a water bath canner and prepare canning jars.
Pour the dandelion tea into a saucepan and add the 2 tablespoons of lemon juice. The acidity of the lemon juice helps balance the sweetness, and makes the jelly safe for canning.
Sprinkle in the powdered pectin, stirring it in until completely dissolved. Bring the mixture to a full boil, then let it boil for 1 minute.
Once the pectin has dissolved and the liquid is boiling, stir in the sugar. This is the point where you can adjust how sweet you want your jelly to be. For standard pectin, use a 1:1 ratio—4 cups of dandelion tea to 4 cups of sugar. If you're using a "low sugar" pectin, you can cut down the sugar to as little as 1/2 to 1 cup, depending on your preference.
Stir the sugar in until it’s fully dissolved, then bring the mixture back to a boil for 1 full minute. You want it to be bubbling and active during this stage.
After the 1-minute boil, remove the pot from the heat. Carefully ladle the hot jelly into sterilized canning jars, leaving about 1/4 inch of headspace at the top of each jar.
After ladling the jelly into the jars, wipe the rims clean, place the lids on, and screw on the rings. Process the jars in the water bath canner for 10 minutes (15 minutes if you’re above 6,000 feet in elevation). Canning is optional, and you can skip it for a refrigerator jelly.
Once processed, carefully remove the jars from the canner and let them cool on a towel on the counter. If the jars seal correctly, they will keep on your pantry shelf for 12-18 months. Refrigerate after opening.