Do Zinnias Reseed Themselves Each Year?

Preparing the Flower Bed

• The key to getting any plant to grow reliably is a well prepared planting bed. Prior to planting your zinnia seeds amend your soil with a good amount of organic material, like compost. Then, add 6-6-6 fertilizer at a rate of 1 pound per 100 square feet of planting bed. Till thoroughly, and sprinkle the seeds over the bed. Lightly tamp the soil when you're done and water. Zinnias require full sun so ensure your planting bed is nice and sunny.

Reseeding

• Zinnias will certainly reseed reliably, but only in warmer areas of the country. They are not frost tolerant, but can produce blooms from early spring until fall in the southern states. Most gardeners dead head spent blooms to encourage the plants to continue flowering. If you want your zinnias to reseed you'll need to let some flower heads mature throughout the flowering season. If reseeded flowers leave gaps in the bed you can bend down tall stems and anchor them to the ground. They'll grow roots and start a new plant to fill in the gap.

Diseases

• There are some diseases that can cause trouble for zinnias. Alternaria leaf spot is a fungal infection that causes unsightly yellow and brown spots on leaves. The fungal spores are spread in the wind and thrive in cool moist conditions. Likewise, powdery mildew can be a problem for zinnia beds. Powdery mildew causes a white to gray, powdery film on leaves, flowers and stems. It also thrives in cool, moist conditions. If these diseases occur, thin your planting bed to improve air flow and light penetration. Gerald Klingman from the University of Arkansas recommends not reseeding and rotating zinnias with other flowers if these diseases are a problem. Alternately, look for resistant cultivars like Profusion.

Other Methods of Propagation

• If you can't get tender zinnias to reseed in your climate there are other options. You can save the seeds from the current year's crop to replant the following year. Place seeds in a paper bag, labeled with the date and type of seed. Place the paper bag in a resealable plastic bag with a tablespoon of powdered milk to act as a desiccant and store the seeds in your refrigerator until spring. Seeds can be sown indoors for earlier blooms or outdoors once the soil is warm enough and all danger of frost has passed. Young plants are also available at many garden centers, although, this option is usually more expensive.