When growing dahlias from seed, you want to start them about 4 to 6 weeks prior to when you plan to plant them outside. By the time you plant them outside, these little seedlings will have already started growing tubers. Dahlias need a minimum of 120 days of growing time in a season to produce viable tubers for the following year. When growing dahlias from seed, it is a mystery as to what the flowers will look like when they bloom. Each seed produces a brand new dahlia variety. For me it’s l...