Year of the Zinnia

Posted by Hilda M. Morrill

February 1, 2011

Every year since 1982, the National Garden Bureau and its members select one flower and one vegetable to be showcased in the "Year of the ..." program. These plants are chosen because they are popular, easy-to-grow, widely adaptable, genetically diverse, and versatile.

According to the Bureau, 2011 has been designated as the "Year of the Zinnia." (Note: We will feature the vegetable selection in our March article.)

For decades, zinnias have been the flowering annual of choice for spreading glorious colors throughout the garden as well as for cutting to bring indoors. But it wasn't always so.

When the Spanish first saw zinnia species in Mexico, they thought the flower was so unattractive they named it mal de ojos, or "sickness of the eye!" Years of breeding have brought striking new colors, shapes, sizes, and growing habits to the humble zinnia. No present-day gardener would ever describe this versatile bloomer as anything less than eye catching.

There are more than a dozen species of zinnias, members of the Asteraceae (also known as Compositae) family. Zinnia elegans, the common zinnia, is very familiar to gardeners.

Tall, mid-sized, and dwarf varieties of this species have been grown for decades, and flowers are available in a wide range of colors. Zinnia angustifolia is less common in gardens, but is gaining in popularity. The plants have narrower foliage and smaller single flowers.

When seeds of zinnias were collected and brought to Europe in the 18th century, the plants were not much to look at. Named for Dr. Johann Gottfried Zinn, who wrote the first description of the flower, the genus Zinnia had to wait for the mid-19th century to become successful in the garden.

The start of the zinnia's real popularity began in the 1920s when Bodger Seeds Ltd. introduced the dahlia-flowered 'Giant Dahlia' zinnia. John Bodger discovered it as a natural mutation in a field of 'Mammoth' and within the next few years selected the large, flat-flowered 'California Giant' from the strain.

Available in separate colors, it was considered to be a new trend in plant habit and flower form, and won a gold medal from the Royal Horticultural Society of England.

Compact zinnias are now "in" - perhaps in response to home gardeners' smaller plots and the popularity of container gardening.

One of the reasons for the popularity of the zinnia is its diversity. Like dahlias and chrysanthemums, zinnias have a variety of flower forms: they may be single, semi-double, or double.

Zinnias also come in an amazing array of colors. Most are solid, but some are bi-colored with a contrasting color at the tip of each petal. You'll find yellow, orange, cherry, pink, purple, scarlet, and white, as well as fashionable chartreuse. Just about every color, in fact, but blue.

Height is an important consideration when planning a garden, and zinnias have growing habits to suit every need. Tall, 3- to 4-foot varieties are best for the middle or rear of a border or in a cutting garden. Dwarf plants grow 8 to 14 inches tall and do well in pots as well as at the front of a garden.

Zinnias are easy to start from seeds, indoors or outdoors. For earlier flowers, and in colder zones, you may want to give the plants a head start by sowing the seeds indoors.

Zinnias grow best in full sun, which means six or more hours of direct sun daily. Don't crowd zinnias; air circulation is essential to keeping them disease-free. Set out plants so that taller zinnias are 12-18 inches apart; dwarf zinnias, 6-8 inches apart; and Z. angustifolia, 6-10 inches apart.

Plant zinnias in the ground at the same depth they were growing in the pots. If you're transplanting from flats or six-packs, try to keep as much soil around the roots as possible so they don't dry out.

One of the nicest aspects of zinnias is that part of their maintenance requirements (if you can call it that), is cutting the blooms frequently to keep the plants compact and bushy and producing more flowers. Planted in the right site in good soil, they are fairly care-free.

Zinnias are often pest free for most of the growing season, but can be affected by two fungal diseases: powdery mildew and alternaria blight. Alternaria blight causes reddish brown spots on both foliage and flowers, and is a problem in the south more than any other area. Powdery mildew can cause Z. elegans varieties to look terrible by late summer or early fall, covering their leaves with a light gray mold. To camouflage the lower foliage of affected varieties of zinnias, plant them with shorter annuals in front.

Although newer plants, such as 'Profusion' and 'Zahara', are very resistant to powdery mildew, preventive care is still warranted. With continued breeding efforts, gardeners may soon see disease-resistant tall zinnias among nursery and seed company offerings, which will give us yet another reason to celebrate this most adaptable and colorful of garden flowers.

Happy Gardening!

(We thank the National Garden Bureau and credit them as our source of information and images.)