By Jim Lakin, M.D., Master Gardener
Not every seed is created equal. Trying to get some of the native perennials to germinate seems to require an Act of Congress. And they’re gridlocked! Not so with the humble but glorious zinnia. In my book, zinnias are some of the most overlooked yet rewarding annuals a Minnesotan could hope for.
Although originating in Mexico and the Southwestern U.S., varieties have been developed all over the world. Yet they all still retain their love of warmth and sunlight, a commodity sometimes in short supply up here. Fear not! Simply sew zinnia seeds after the last hard frost and bide your time. As things warm up the seedlings will take care of the rest, producing blooms from late spring, far into the fall.
If you have a warm sunny spot inside, you might even consider starting some seeds four to six weeks before the last frost. Unlike some more persnickety plants, zinnias germinate readily. You can set them out in the garden when they get two to four inches tall and enjoy weeks of blooms before the seeds you sewed get in gear.
There are many varieties of zinnias ranging in height from 6 inches to 4 feet. I like the older, smaller blooms. They are hardy, fast growing, and tough plants. As I said, they do need full sun and warmth, but ask little else. One fertilization a season usually suffices. They are quite disease resistant. Powdery mildew seems to be the only common malady. It doesn’t look very attractive, but the plants usually survive. To keep them happy and mildew free, select a well-drained location for planting. Zinnias don’t like their feet wet.
If you find a variety you really like, consider collecting seeds in the late fall. Just cut off the spent flowers, shake out the seeds onto a sheet of paper, slip them into an envelope and store in the fridge until early next spring to start indoors or sew in the garden a bit later. Either way you will have bold, bright colors to cheer you through the gardening season!
Want to learn more about zinnias than you thought there was to learn? Try Eric Grissell’s new book, A History of Zinnias: Flower for the Ages, Perdue University Press, West Layette, IN, 2020.