Maintaining a cutting garden that provides fresh flowers all year long is one of my favorite garden activities. Zinnias are a popular addition to spring cutting gardens but most people don’t realize that zinnias can be planted into the late summer and enjoyed throughout the fall. Zinnias thrive in hot weather and germinate easily from seed. Fall growing conditions are perfect for zinnias because the weather is usually a little dryer. I recommend seeding zinnias by August 15th to enjoy them throughout the fall. They will die out after the first frost.
Zinnias prefer full sun and well-drained soil. Plant seeds 9”-12” apart. Zinnias produced for cut flowers benefit from pinching when they are young. Pinching encourages branching and longer flower stems. Pinch off the new growth after the 2nd or 3rd true leaf set. You only need to pinch once. Cutting zinnias also promotes more branching and flowering. If you prefer to leave your flowers on the plant, I recommend deadheading the spent flowers.Deadheading is the practice of removing old flowers to prevent disease and encourage new growth.
Zinnias are drought tolerant but may require irrigation during dry periods. Try to avoid overhead irrigation. Use a soaker hose, drip tape, or simply let your hose drip at the base of the plants. Watering at the base of the plants prevents the spread of disease. Anyone who has ever grown zinnias has probably seen zinnia leaf spots. Zinnia leaf spots start at the base of the plant and work their way up the leaves eventually killing off the plants. Zinnia leaf spots are caused by different fungal diseases and can be managed with fungicide sprays. I normally don’t recommend spraying zinnias because you will have plenty of time to enjoy them before the spots take over, but if you must spray, try rotating mancozeb and myclobutanil (Spectracide Immunox) every seven days to fend off the spots.
There are a plethora of zinnia seed varieties available online but I have plenty of success with whichever variety the local garden center carries. I recommend trying them all! The Benary Giant, State Fair, and Cactus Flowered Mix are old favorites. Good luck!
Jessie Hoover is a County Agent with the LSU AgCenter covering horticulture in East Feliciana, West Feliciana, St. Helena, and Tangipahoa parishes. For more information on these or related topics contact Jessie at 225-683-3101 or visit www.lsuagcenter.com.
Benary Giant zinnia starting to open. Photo by Jessie Hoover.
Zinnia leaf spots. Photo by Jessie Hoover.
The LSU AgCenter and the LSU College of Agriculture