An excerpt from the film Solve Et Coagula, The Creation of Elixirs is a summary of Plant Alchemy or Spagyrics, and goes into some practical methods for getting started in the Sacred Art and Science.
We talked about this some - but wanted to answer and expand here for the benefit of others as well. It depends on a variety of factors, such as the herb being used, the ruling planet, the day and hour, many factors as to potency and effects. When created and used as a complete set for each of the seven days, an internal balance is reached on subtle levels, as well as the physical healing that takes place for each herb, which is completely up to you depending on what you want to include.
Its good to experiment a bit as well, some Sunday herbs for example may have more subtle or medicinal effect than others.
Personally, I did feel that Basil (mars) was especially potent as well as Fennel (Mercury), which has quite an electric charge of liquorice flavor.