Step 1: Collect fresh dandelion heads from a clean, pesticide-free area. Pluck the yellow petals away from the green sepals until you have 2 cups of petals.
Step 2: Place petals in a heat-proof bowl and pour 4 cups of boiling water over them. Let steep for at least 8 hours or overnight.
Step 3: Strain the dandelion tea through a cheesecloth, squeezing well to extract all liquid. Measure out exactly 3 1/2 to 4 cups of the liquid.
Step 4: In a large pot, combine the dandelion liquid, lemon juice, and pectin. Bring to a full rolling boil over high heat.
Step 5: Add the sugar all at once. Stir constantly and return the mixture to a full rolling boil that cannot be stirred down.
Step 6: Boil hard for exactly 1 minute, stirring constantly. Remove from heat and skim off any foam with a metal spoon.
Step 7: Ladle hot jelly into sterilized jars, leaving 1/4 inch headspace. Process in a boiling water canner for 10 minutes.