How to Prepare Zinnias for Mild Winters

Zinnias need warm weather to perform well.

Zinnias are annuals. They live for one year, one growing season, and die back when exposed to frost. Because of these facts, there is little to do to prepare your zinnias for even a mild winter. Even with added protection, the flowers are unlikely to survive beyond late fall or early winter.



Those in southern regions may have the best chance of extending the viability of their zinnias; however, zinnias grow poorly in cool weather. Even if you prevent the death of your plants, the plants may fail to continue to produce blooms.

Things You'll Need

• Plastic sheeting

Instructions

1. Take protective measures before temperatures drop. Plant your zinnias in a location that is unlikely to build up cold air, such as a raised area or on a hillside. Plant away from fences, hedges or wooded areas, as the North Carolina Cooperative Extension Service suggests these locations can dam cold air; they may see frost early in the season and more often than other locations.

2. Cover the plants with plastic sheeting or another protective barrier that preserves the temperature around the plant to provide some protection for your zinnias from the tissue damage caused by frost. Heat stored in the soil warms the air around the plant with this method; however, once the temperatures drop severely, there will no longer be sufficient retained heat to provide this protection.

3. Avoid taking drastic measures to protect your plants. Advective frosts feature low temperatures. Plants exposed to these frosts typically require more complex protective methods, including the use of heaters, wind machines and overhead sprinklers. These methods are complicated, expensive and labor intensive. These are unlikely to be worth the trouble for preserving a warm-weather annual plant.

4. Preserve your zinnias outside of the garden. Zinnias can be preserved through pressing. Place cut flowers between sheets of paper, and cover the papers with a heavy object, such as a stack of books, to sit for two to four weeks. You can also try drying your flowers using silica gel, sand or another drying agent. Double flowers dry best, according to Iowa State University's Reiman Gardens, and zinnias last a week as a cut flower.

Tips & Warnings

• Plastic tunnels and fabric row covers provide temperature protection of 2 to 4 degrees F. Plants must be uncovered or ventilated each morning. Wall-of-Water devices are made to protect a single plant or small group of plants. As they will not protect taller plants that extend beyond the devices' upper rim, they will not protect some zinnia cultivars.

• Cold frames are made to sustain cool-season crops; they are unsuitable for warm-season zinnias.

References

• University of Florida IFAS Extension; Zinnia spp. Zinnia; Edward F. Gilman, et al.; 2009
• Oregon State University; Plant Life Cycles; Ann Marie VanDerZanden
• Clemson Cooperative Extension; African Zinnia; Dr. Dave Bradshaw
• University of Illinois Extension; Preserve the Pleasure of Your Garden; David Robson; Aug. 31, 2010
• North Carolina State University Cooperative Extension; Frost/Freeze Protection for Horticultural Crops; Katharine B. Perry, Ph.D.; March 1994
• Iowa State University Reiman Gardens; Zinnias; Cindy Haynes, et al.; June 2008

Resources

• University of Illinois Extension; Plant Palette -- Zinnias; Jennifer Schultz Nelson; June 1, 2008
• Colorado State Univ. Extension; Frost Protection and Extending...; David Whiting, et al.; June 2007
• University of Arizona; Frost Protection; Lucy Bradley; April 1998