How to Grow Zinnias

Staking: These flowers have sturdy stems, so do not need staking.

Watering: Zinnias need moist soil to grow their best. This is especially true of young plants. Water deeply a few times a week so the soil stays moist 6 to 8 inches deep. Don't overwater because zinnias can also succumb to rot diseases especially on wet, clay soils. Once established, zinnias a relatively drought tolerant.

Fertilizing: Amend the soil before planting zinnias with compost. When flowers start to form, side dress with an organic 5-5-5 fertilizer to get more and bigger blossoms.

Mulching: Mulch zinnias once they are established with a 2 inch layer of straw or bark mulch. This will help preserve soil moisture and prevent weed growth.

Trimming & Pruning: Deadhead (trim) spent flowers regularly to promote more flowering and to keep the plant tidy. To create bushier plants on tall varieties, pinch the growth tip of the plant when young. This will stimulate more side branching, a shorter plant, and more flowers. However, it may delay flowering, especially in cool summer areas.

Zinnias: End of Season Care

Dividing & Transplanting: Zinnias are annual flowers so don't need dividing. However, they can be finicky about being transplanted. If growing them indoors for transplanting, use larger peat or plastic pots so you don't have to transplant more than once. Try not to disturb the roots when moving the plants.

Pests & Disease: The biggest pests of zinnias are powdery mildew disease and Japanese beetles. Powdery mildew disease is especially prevalent in humid areas of the country in late summer. A white film develops on the leaves. Eventually the leaves turn yellow and drop. The whole plant can quickly get infected making it look messy and reducing its overall flowering. To prevent powdery mildew, space plants further apart to increase air flow, grow disease-resistant varieties, and apply preventative sprays early in the season. Neem oil and Serenade (Bacillus subtilis) are two organic sprays that work well to prevent the spread of powdery mildew. You can make your own organic spray by adding 1 tablespoon baking soda to 1 tablespoon of horticultural oil in 1 gallon of water. Aphids also can attack zinnia leaves causing them to curl and yellow. Knock aphids off zinnia leaves with a strong spray of water from a hose.

Japanese beetles love zinnias and are often found feeding and shredding the leaves. To control Japanese beetles, apply beneficial nematodes or milky spore powder in the early summer and fall to kill the c-shaped, white grubs in the soil. These are the larvae of the adult beetles. Use beneficial nematodes in colder areas. To reduce the adult beetle population in summer, set out Japanese beetle traps at least 200 feet away from your garden in a perimeter around your property. In this way, the flying beetles will find the traps before they find your plants. You can also handpick the adults in the morning while they are sluggish and drop them in a pail of soapy water.

To learn more about the seeds & plants we sell and how to grow them in your garden beds and patio containers, sign up for our inspiring emails.

Learn More About Zinnia