Gather the ingredients.
Soak petals in cold water for five minutes to allow time for any insects to exit, then drain.
Place petals in a heavy saucepan along with water, lemon slices, and vanilla bean.
Bring to a boil over high heat, then reduce heat, and simmer for 30 minutes.
Remove pan from heat and let steep for 6 hours.
Strain dandelion tea through a cheesecloth and discard solids.
Place dandelion tea in a heavy saucepan and bring to a low boil.
Gradually add sugar to boiling liquid while stirring until sugar is dissolved.
Lower heat and let simmer uncovered until it reaches desired syrupy thickness. This may take about 1 hour. It will thicken more as it cools.
