Types of Zinnias
There are three main types of zinnias: Single, semi-double, and double blooms. Single-flowered zinnias feature a single row of petals. Semi-double zinnias have thick rows of petals, but visible centers. Double-blooming zinnias feature thick petals that completely obscure their centers.
Beyond the three main classifications, there are plenty of zinnia cultivars to choose from, depending on your location and how you intend to use them. Zinnia elegans and Zinnia bicolor, heat-loving cultivars originally from Mexico, are two of the most commonly planted, but heirloom varieties like large double-flowered Benary’s Giants, and dwarf spreading varieties like Thumbelinas are also commonly cultivated.
How to Plant Zinnias
Like marigolds and dahlias, zinnia flowers are a sure-fire way to attract pollinators to a vegetable garden. Create a terraced effect in a garden bed with taller varieties, and use shorter varieties to edge vegetable gardens or create borders along fence lines.
- Pick the site. Zinnias are well-suited for USDA hardiness zones 3–10. Plant zinnias in a site where they’ll get full sun, at least six hours a day.
- Prepare the site. Work some organic matter into well-draining soil before planting, aiming to achieve a soil pH between 5.5–7.5. Amending the soil with compost will speed the flowering process.
- Plant. Zinnia seedlings do not tolerate transplanting, so it’s best to start zinnia seeds directly in the ground well after the last frost date in your area. Sow seeds ¼–inch deep. Space plants anywhere from a few inches to a few feet apart, depending on the variety.
How to Care for Zinnias
These annual flowers will typically die off with the first frost of late fall, but if you allow the final round of blooms to fully mature and scatter its seeds, they’ll return the following year.
- Water. Zinnia plants need about an inch of water per week, but may require more in warmer climates or during heatwaves. Always monitor the dampness of the soil to strike the right balance, and water at the root, not from above, to avoid overly damp foliage.
- Mulch. A light layer of mulch will help to regulate both weeds and maintain soil moisture.
- Thin seedlings. Good air circulation between zinnia plants is crucial in preventing fungal diseases like powdery mildew, so thin plants to a minimum of six inches apart once seedlings reach three inches tall.
- Deadhead. Regular deadheading (removing wilted or dead blossoms) encourages the plants to continue producing blooms through the growing season.
- Control pests. If you notice spider mites making themselves at home among a zinnia flower’s leaves or blossoms, pinch off the affected areas to prevent spreading.
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