Zinnias, which come in myriad shapes, sizes, and colors (excluding blue), are some of the toughest annuals you can plant. They're also a pollinator favorite. Low-growing zinnias are perfect for borders. Taller varieties, which reach several feet high, make an excellent choice for cut flowers.
Zinnias' many different colors and floral types add interest to cutting gardens. Floral options include both cactus and quill-type blooms with long, narrow petals, and pompom-type blooms that look like little spheres. Since zinnias come in a variety of colors, they can work well in almost any flower arrangement. Zinnias are a favorite with pollinators such as butterflies that like to land on the flowers and drink their nectar. While taller zinnias suit cottage and cutting gardens, their lower-growing, creeping, or spreading relatives work well in containers. The latter types also require less frequent deadheading than their taller counterparts.
Zinnia Care Must-Knows
Native to grassland areas, zinnias are tough plants that handle drought well. Even though they grow best in well-drained organic soil, zinnias are extremely tolerant of poor soils, including hard clay. No matter where your zinnias grow, they will benefit from a slow-release fertilizer and the occasional liquid feed to keep them blooming all season long. This is especially true in container settings filled with a soilless potting medium.
Because they come from prairie settings, zinnias prefer full sun. This environment nurtures the best bloom development. It also helps keep plants dry, which prevents common diseases such as powdery mildew—a condition most commonly seen as a white powder found on the plant's bottom leaves. While this pesky fungus probably won't kill the plants, it does diminish their beauty. The best control method for powdery mildew is prevention; look for resistant zinnia varieties and keep plenty of airflow around the plants.
Leaf spot and blight are two more common diseases found in zinnias. Similar to powdery mildew, these conditions are caused by fungi. Control methods are the same: Remove any debris from the base of the plants to keep them clean. Many of these fungal diseases are found on the lower leaves of taller zinnia varieties used for cut flowers. Place shorter plants in front of taller zinnias to hide their naked stems.
Saving zinnia seeds is a good way to start next year's plants. Because many zinnias are sold as mixes, you don't have to worry about seedlings being identical to the parent plant. As old flower heads dry, remove spent blooms and harvest the small arrowhead-shape seeds from between each of the petals. Zinnia seeds can be started directly in the ground the following spring.