When you are first establishing a perennial garden you will probably buy all of your plants from a nursery, garden center or an online mail order gardening company. However, one of the great advantages of perennials is their ease of propagation. By the end of the first season you will have quite a few large plants ready for dividing.
I’ve divided my Hostas, Rudbeckia (Daisies), heuchera and astilbes several times. Some perennials, such as peonies, will grow for many years without needing to be divided. Some, such as peonies, will grow for many years without needing to be divided, and may not recover quickly once broken up, but to maintain their vigor most perennials need dividing at least every three years.
Many perennials can also be grown from cuttings, usually of the fast growing spring shoots.
Annuals must be raised from seed. You can do this for yourself or buy ready to plant seedlings from a garden center. I’ve found that by growing several of my annuals from seed I tend to have access to a wider variety of types of annuals and or colours as opposed to the offerings at most garden centers and nurseries which tend to sell the most popular varieties of annuals.
For small quantities, raising your own seed is seldom cheaper than buying seedlings, but if you have large beds to plant out, raising your own plants often represents a considerable saving.
Seed sowing and germination are usually fairly straight forward. In many cases the seeds may be sown directly where the plant is to grow in the garden bed. Some annuals need to be started in late winter or very early spring indoors in order to be large enough to plant out come late spring or early summer.
Most perennials and bulbs are planted in early autumn or early to mid-spring, whereas annuals are often started indoors in February or March and planted as seedlings from mid-May through June; or purchased as seedlings in late April and May and planted out after the last frost.
Enjoy your lovely garden.