Mullein gold colour is not from the flowers, but the LEAVES.
The longer silk is left in a strong dye bath the more colour it may absorb, for a stronger and deeper colour. This looked dark, and I washed it out, but it could have been darker if left over night. A small piece of silk will not be able to absorb all the dye, so a secondary piece can be added later.
I may not have used a mordant (such as alum), as colour dried light gold beige. A good neutral background for painting on.
Many plants produce a dye for cream, beige, or gold; which is very useful background for silk painting on, rather than stark white. Intensity varies. More antique tone can be achieved by adding ferrous water to the dye bath. (iron - made from rusty nail water). Other metals could be experimented with. Copper will have an effect. Making the dye bath in copper pan has an effect.