Larkspur is what is called a hardy annual. They easily self seed year after year in the same patch and they are very cold hardy. They can be direct sowed very early in the season and sown in succession to have continuous blooms. Place seeds in the freezer for a few days before planting. Harvest after 1/3 of the blooms are open.
I grew these for the first time last year and was not that impressed. They are very dainty flowers that can easily get overwhelmed by other larger blooms. However, what did impress me was that this year, I have an entire thick patch of them that came back on their own out in the flower field. They came up early and are now blooming naturally in June for the first time.
Here is the first bouquet of the year that I made using larkspur, smoke bush, penstemon, viburnum and one stem of delphinium.