Remove the dandelion petals from the green flower base, resulting in 2 to 4 cups of petals. Put the petals in a large heat-safe bowl or container. (The green bits will add bitterness and must be removed)
Pour 4 cups of boiling water over the petals and steep in the fridge for 24 hours
Strain as much liquid out of the petals as you can (should get between 3 and 4 cups of dandelion tea). Squeeze the petals to get all of the flavorful goodness into the tea.
Combine your dandelion tea, lemon juice, and powdered pectin in a large pot. Bring to a boil.
Add sugar and return to boil. Boil for 1 to 2 minutes.
Remove from heat and skim off any white film.
If not water-bath canning: ladle the jelly into clean half-pint jars. Label them! These can be kept in the fridge for many months or can be put in the freezer for longer storage (leave at least 1/2" headspace if freezing).