September is the time of seasonal change when plants near the end of their cycle and set seed. Perennial flowers go to seed and then die back to a dormancy state for the winter. The above the ground parts of the plant are cut back after frost to about six inches above the soil surface and the root system rests till the following spring. Annuals grow to maturity, go to seed and die, as the life cycle is over in one growing season.
The rules for gathering seed are generally the same for most of our annual flowers but here we focus on the zinnia.
Zinnias will reseed themselves, so it you like where they were located or just don't get to gathering any of them, let them alone to dry on the stalk and clean up the old plants in the spring. Between the wind and the birds those seeds will be scattered here and there without any efforts from you. But if you want to choose certain colors or want to have seeds to put in another area, then here is how to do it:
Zinnias are a favorite for anyone wanting a flowerbed to attract butterflies, hummingbirds and insect pollinators. They are easy to grow, come in a wide array of colors, bloom all summer long, are drought resistant, pest hardy, not fussy about soil and if you choose, you can get varieties up to five feet tall. These beauties from Mexico do love the sun and warm weather so it is important to wait till the soil warms up in the spring to plant the seeds.
Only save seed from open-pollinated varieties. There are some hybrid zinnia types that won't grow true to the parent from saved seed. Here is a list of varieties that are open-pollinated:
State Fair Mix
Cut'n Come Again
Choose the strongest, biggest blossoms for seed saving. Though cutting off the spent flowers is tempting because of their unsightliness, resist the urge if you want the seed. The only way to get the seeds is to let the pods dry out on the plant.
These flowers are drying but not ready yet to cut off:
The flower head has to be completely dry. It'll be dark brown and dry when ready to cut. Trying to harvest too early will result in immature seeds that won't germinate. Choose the ones you want and deadhead the rest. You won't need to save every flower unless you plan on selling them or giving them away. For your own use you'll be surprised how many seeds come from just one flower head.
Cut off the dried flower heads and choose one of two ways to prepare to save them:
Some people just put the entire seed head, petals and all, into a paper bag and store them in a dry, cool, dark place for the winter.
Other people like to do the work now rather than in the spring.
The dried petals need to be pulled off and the seed cone torn apart to gather the seeds. It'll be messy so do it over a tray or something to catch the seed and separate them from the dried petals. Once you pull off the dried petals, what you'll be looking at is an arrow-shaped base which is the seed bundle. This bundle is torn apart to expose and separate all the seeds.
The other method of storage is refrigeration or freezer. This eliminates the three risks to seeds which are heat, air and the problem of condensation. The deterioration process is halted and seed can last for years with little drop in germination rates. Put the seeds in ziploc plastic bags or tightly sealed containers and store in your refrigerator or freezer till needed. In the late spring when you pull out those seeds, don't take more than you plan to plant at the time. You don't want the seeds defrosting and then putting those you don't need back into the cold.