While many gardening aficionados appreciate the visual charms of both zinnia (Zinnia spp.) and dahlia (Dahlia spp.) flowers, each plant is distinctly its own self, despite their somewhat similar basic outlines. Zinnias thrive in USDA zones 2 through 11. Dahlias are hardy in U.S. Department of Agriculture plant hardiness zones 8 through 10.
Dahlias run the gamut in terms of size. The flowering plants come in hundreds of different types. The diameters of their flowers all differ, too. Some of the flowers have diameters of merely 1 inch. Others are markedly larger, with diameters of 14 inches and more. Zinnias are also extremely diverse as far as size goes. Some have diameters of 1 inch, just as with dahlias. Others, however, have 7-inch diameters. Dahlias and zinnias are similar in their size diversity, although their sizes frequently differ depending on factors such as species.
Flower and Petal Arrangements
Dahlias and zinnias both have varieties with single, semi-double and double petals. You can see the centers of the flowers in both semi-double and single specimens, but not in double flowers. Dahlias come in both single- and double-flowering varieties. Semi-double and double-flowering plants have significantly more petal rows than those of their "single" counterparts.
Diverse Flower Coloration
Some zinnias bloom in pure colors, while others have combinations of colors. This also applies to dahlias. Some dahlias, for example, have striped flower petals. Zinnias and dahlias both brighten the garden by blooming in a wide range of colors. Zinnia flowers can be orange, purple, red, gold, pale green, lilac, pink, off-white, white or yellow -- essentially every color except black, brown and blue. Dahlias bloom in yellow, red, pink, orange and purple, and some of the dark purple shades are close to black. They also come in practically all colors, but not in bright blue.
Zinnia flowers are diverse in their basic outlines. Some of their shapes resemble balls and domes, while some are more circular. Many have shapes similar to certain dahlia types -- somewhat flat and big. While some varieties of dahlias have flowers with ball-like forms, others are considerably flatter in appearance. If you want an opportunity to explore all of the visual potential in dahlia flowers, pay attention to them when they're in season -- from spring into the beginning of the summer.
- Wisconsin Horticulture: Zinnias
- Ohio State University Extension: Growing Dahlias
- WSU Extension -- Spokane County: Dahlias
- University of Georgia College of Agricultural & Environmental Sciences: Dahlias
- Utah State University Cooperative Extension: Growing Dahlias
- North Carolina Cooperative Extension: Dahlias for the Home Landscape
- Clemson Cooperative Extension: Summer and Fall Flowering Bulbs
- University of Illinois Extension: Zinnias
- Colorado State University Extension: Zinnias
- University of Vermont Extension: The Year of the Zinnia
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