Bring 4.5 cups of water to a boil and pour over the dandelion petals in a bowl. Allow to steep for one hour. Either use immediately to make jelly or place in the fridge for 24 hours.
Place 3 cups of sugar in a bowl and take 1/4 cup of sugar from the bowl to combine with the Sure Jell in a separate bowl.
Pour the tea into a large pot on the oven. Add the lemon juice and the Sure Jell that has been combined with 1/4 cup of the 3 cups white sugar. Bring the tea mixture to a rolling boil and pour in the remaining white sugar all at once. This will bring down the boil. Bring back to a rolling boil. Allow to boil for exactly one minute. Remove from heat
Ladle the jelly into clean jars, wipe the rims with vinegar, and place the lids on top. Tighten the bands finger tight.
Process the dandelion jelly in the water bath canner for 10 minutes (adjust for altitude.)
Remove the jars from the water bath canner and allow to sit undisturbed for 24 hours.