A well-appointed garden needs not only flowers but also decorative foliage that is concurrently available to combine with the garden flowers in a vase.
This genus of plants are commonly called anise hyssops and are in the mint family.
Just about any herb you grow can be used as filler to increase the impact of a few garden flowers in a vase.
At certain times of the year we just don’t have quite enough flowers. This is when "filler" is really important.
Mint grows so well in the ground that it is difficult to grow just a little of it.
There are over 900 species of salvias, and it is the largest genus in the mint family.