Arguably one of the hardest working flowers in the garden, zinnias (Zinnia sp.), pull their weight in terms of the length of blooming season, required care, and sheer beauty. Zinnias are available in hundreds of different varieties ranging from the size of a quarter to a grapefruit. With minimal attention, zinnias will bloom from late spring through early fall and are sure to brighten up your landscape.
Native to Mexico, zinnias are annuals that prefer warm to hot weather. When selecting zinnias for your landscape, make a note of the growth habits of each variety. Mature plant heights range from less than 1 foot up to 4 feet with equal spread. Low-growing zinnias do well in containers and as a garden border. Powdery mildew is a common problem among zinnias grown in humid climates. Proper spacing allows adequate air flow which is one of the best defenses against powdery mildew. You can also choose a variety of zinnia that is resistant to powdery mildew.
Zinnias thrive in full sun without much concern for soil type though well-drained soil is ideal. Seeds can be started directly in the ground, but zinnia seedlings can be transplanted successfully once the danger of frost has passed. While the plants tolerate dry conditions, the number and quality of blooms may be negatively impacted, so it is beneficial to provide regular water, especially during droughts. While the plants are young, supplemental water every two to three days keeps them from becoming stressed. Mature plants may only require a weekly watering.
Zinnias make outstanding cut flowers and will last over a week in a vase when clean water is provided. Cutting flowers from your plants regularly encourages them to continue to send out blooms throughout the growing season and promotes stronger, healthier stems. If you are growing zinnias for cut flowers, consider staking the plants. Without support the stems of the taller varieties can bend under the weight of the many blooms. The bends are difficult to incorporate into a floral arrangement but also can cause the stem to snap at the node.
Due to the relatively large seed size and the quick growth, zinnias are a great option for young gardeners. Zinnias also attract butterflies. The blooms can be single, double or somewhere in between. Single blooms have a row of petals surrounding a visible center. Semi-double flowers have the visible center but also multiple rows of petals surrounding it. The blooms with the visible center tend to attract more butterflies than the double blooms, which have many rows of petals with no visible circular center to the flower. Some varieties have flowers that look similar to a dahlia. Others have a resemblance to cactus blossoms while some varieties have stacked rows of petals that create a beehive appearance.
If you’re looking for a place to start your cut flower garden, zinnia elegans makes a great addition. It is a timeless classic with showy flowers. For the border or container plantings, zinnia angustifolia, is a good choice. Beyond these two common varieties, there is a world of zinnias to explore. Though variable in color, texture and size, none of the blooms will disappoint.
Cynthia Domenghini is an instructor and coordinator for K-State’s horticultural therapy online certificate program.