All About Zinnias
These fun and fabulous flowers offer a variety of benefits in the landscape. Learn how you can spice up your garden with pollinator friendly plants.
These days, there’s a lot of hype surrounding monarch butterflies and honeybees. Many gardeners have become concerned about doing their part, and environmental stewards have been quick to offer suggestions. Topping the suggestion list is creating a home garden centered around pollinator-friendly plants. The horticulture industry has seized the opportunity to market plants — often at inflated prices — but advertisements as to what and where to plant are often confusing, and purchasing plants at any cost can hurt a family’s budget. But don’t despair! There’s an easy fix to this dilemma.
First, close your eyes and think back to the backyard summer garden of your parents, grandparents, or even great-grandparents. Those vintage gardens were both showy and practical — and oftentimes, the plants didn’t even cost a copper cent.
Take my family’s garden, for example. In the mid-1900s, my childhood home was in a middle-class neighborhood in rural New Orleans. My father was passionate about gardening. Our small backyard was a busy space, with a major grassy area for pets and children, a clothesline, a metal swingset, a small utilitarian shed, and a strip of tilled soil flanking the back wire fence. The tilled venue was dedicated to the cultivation of seasonal vegetables, along with an eye-popping, flowering plant called a “zinnia.” The fresh vegetables were destined for the dinner plate, whereas the colorful, large flowers wound up in a canning jar that served as the centerpiece on our kitchen table.
Later, when the growing season ended, various vegetables and flowers were strung in the shed to dry for next year’s seed supply. The key to our successful and economical garden was my father’s single rule of thumb: “If you can’t grow ’em from seeds, forget it.”
We planted everything from seeds. These were initially secured from a generous neighbor or friend, or occasionally purchased from a hardware store or garden catalog. If purchased, the packets of seeds were inexpensive and easily shipped. By embellishing both the exterior and interior of our home, the zinnia was an acknowledged fabric of our summer garden, and from what I remember, our garden was always the showpiece in the neighborhood. At summer’s end, my father frequently shared his bountiful seeds with interested neighbors.
About the Zinnia
Zinnias are warm-weather annuals that are members of the Asteraceae family, more commonly known as the aster or sunflower family. This is the largest singular grouping of flowering plants in the world. With more than 1,500 genera and nearly 25,000 species, familiar examples include not only the patriarch sunflowers and asters, but also daisies, marigolds, coneflowers, chrysanthemums, dahlias, black-eyed Susans, dandelions, thistles, and, of course, zinnias. All are characterized by having flower parts arranged in a circle or star pattern, hence the family name “aster,” the Greek word for “star.”
Zinnia blossoms are complex. Each blossom isn’t a single flower at all, but instead a tight assemblage of multiple flowers called “ray flowers” and “disk flowers.” Ray flowers are the conspicuous petals that are arranged in an outer whorl. On the other hand, disk flowers lack petals, but contain pollen- and nectar-producing reproductive parts (the source of seeds) that are confined to the flower’s center. Because of this unusual arrangement, plants within the family are commonly called “composites.”
The body plan for a rank-and-file zinnia plant is simple. Leaves are opposite, and attached directly to a major stem (no petioles); leaf shape varies from linear to ovate, but is always dull-green with sandpaper-like texture. As plants age, the stem produces secondary branches, each terminating with a solitary blossom.
Flowers are spherical, of course, but petals vary in number and size. The simplest form is referred to as “single,” in which one row of ray flowers surrounds the central, tightly packed disk flowers. But then morphology becomes rampant. The whorls of ray flowers can double, triple, and even appear as a pompom (an arrangement in which all disk flowers are obscured or even missing). None, however, produce a noticeable fragrance, which is perhaps the zinnia’s only negative trait. This is more than compensated for, however, by its longevity, as a typical flower (either in the ground or a vase) can remain fresh for three or more weeks.
Finally, color is kaleidoscopic, except for blue. There’s even a pure-green cultivar, which is a horticultural rarity. For me, the magenta hue is particularly evocative. The color is often so subtle in the low light of dusk that a flower can fool an observer into thinking it’s a handcrafted, crushed-velvet look-alike.
For the modern homemaker, today’s zinnias are decidedly more diverse than their forerunners. All, however, are derived from tropical stock that’s native to relatively dry habitats, such as the grasslands of tropical America, especially Mexico. With such a pedigree, zinnias are intolerant to cold and wetness. In addition, because zinnias are reputed to repel white flies, a common pest, the plants act as pest control in complex gardens. Also, for rural areas with deer intrusions, the rough nature of the leaves renders the plants unattractive to browsers.
Based on growth form, zinnia plants can be separated into three basic categories: tall, short/spreading, and cactus-flowered. Within each category are numerous variations. (See “Zinnia Categories” below.) Seeds are exceptionally fertile, and plants are easy to cultivate as long as a few basics are observed. (See “Growing Tips” below.)
Zinnias are proven “magnets” for butterflies, hummingbirds, and other pollinators. Varieties with fewer ray flowers (petals) and more disk flowers (reproductive parts) are the most attractive. In my own zinnia patch in Baton Rouge, Louisiana, for instance, I’ve logged in a dozen or so species of butterflies gathering nectar on a single summer day, and for a typical season, I can amass around 60. I theorize that the combination of large flower size, bright colors, high-octane food concentrated within a single inflorescence, and an inherent genetic program for heat and drought resistance all combine to enable the zinnia to rank as a “super plant” for both humans and pollinators.
The bottom line is that the addition of zinnias to your summer garden, regardless of size and geographic location, guarantees rewards for both you and nature in general. Moreover, the colorful display just might make your neighbors want to become environmental stewards as well. After all, no gardener can afford to overlook the zinnia.
• Plant or sow in full sun. In hot climates, select venues with afternoon shade.
• Provide well-drained soil that’s on the sandy side and, preferably, slightly acidic. In hot locations, mulch heavily.
• Maintain soil on the dry side, because many varieties are subject to leaf mildew.
• Fertilize lightly. (Heavy nitrogen encourages vegetative growth over flower production.)
• Deadhead tall varieties for increased blooms.
• In the Deep South, where powdery mildew is often a problem, discard plants in late summer, and introduce a new crop for autumn blooming.
• In northern venues, sow seeds in germination trays indoors in early spring, and then relocate the sizable plants outdoors following the last frost.
Keep Cut Flowers Fresh
To prolong freshness in cut flowers, each day trim them at a 45-degree angle, about 1⁄2 inch from the bottom of the stems, while holding them underwater to keep air from entering the stems. Some horticulturists suggest adding a commercial flower preservative to the vase, but many home gardeners prefer to add one or more of the following: a crushed aspirin, a tablespoon of lemon juice, a tablespoon of lemon-lime soda, a pinch of sugar, or a few drops of bleach. Theoretically, these ingredients facilitate water transport in the stem, acidify the water for better metabolism, increase energy available to the flower, and hinder the growth of mold and bacteria in the water. Because of the wide variance in commercial water supplies, specific results may vary.
Zinnia plants can be separated into three basic categories, as follows, and there are numerous variations within each category.
• Tall Varieties
These are the heirloom zinnias that were the mainstay of vintage summer gardens. Plants can grow up to 3 or 4 feet in height and produce flowers that can be saucer-sized, rendering them excellent for cutting and displaying indoors.
Large swallowtail butterflies are particularly attracted to tall varieties, because the super-sized blooms provide excellent landing platforms. To encourage flowering, spent flowers should be deadheaded. Because of their height, tall zinnias can be easily damaged by strong winds and rain. To offset, plant in masses or beside a structural wall or heavy shrubbery.
Commercial producers have isolated many cultivars based on flower color. Examples include ‘Benary’s Giant Mix,’ ‘California Giants,’ ‘Burpeeana Giants Mix,’ ‘Dahlia Flowered Mix,’ ‘Bon Bon Mix,’ ‘Envy,’ ‘Candy Stripe Mix,’ ‘State Fair Mix,’ ‘Peppermint Stick,’ ‘Forecast,’ and ‘Polar Bear.’
• Short/Spreading Varieties
These forms remain short and compact, and they work exceptionally well as edge plantings or in masses for foreground plantings. The oldest spreading variety is the “Crystal” series,” which features ‘Crystal White,’ ‘Star Gold,’ and ‘Star Orange.’ These are narrow-leaf forms that resemble their wild ancestors. Although the plants remain short, they tend to be less compact and more “leggy.” Ray flowers are single, whereas disk flowers are numerous and conspicuous. These forms don’t require deadheading for nonstop blossoming.
Specialty cultivars include ‘Profusion,’ ‘Zahara,’ ‘Thumbelina Mix,’ ‘Pepito Mix,’ and ‘Lilliput Mix.’
In southern Louisiana, the most popular spreading zinnias are the ‘Profusion’ and ‘Zahara’ series. Ray flowers are medium in size, tight in organization,
and available in single and double forms with a wide range of colors. As an added bonus, the vegetative parts of the plants are relatively resistant to powdery mildew, which is usually a major problem for my garden. Because of their compactness and heat resistance, the plants are excellent as container plantings on patios.
• Cactus-Flowered Varieties
These plants can reach 30 inches in height, but flowers are different from those of the tall varieties. Ray petals are extra-long with spiked (pointed) tips that habitually twist and curl as they bend downward. Nonresistant to mold, the plants are unreliable in the Deep South. (Tip: Use ground soakers to avoid wetting leaves, and water only in the morning hours on sunny days.)
Specialty cultivars include ‘Cut-and-Come Again,’ ‘Super Cactus Giant Mix,’ ‘Cactus Flowered Mix,’ and ‘Magellan Mix.’
Gary Noel Ross is a retired professor of entomology and an award-winning nature writer. He enjoys directing butterfly festivals for the North American Butterfly Association, as well as exploring the swamps and marshes of Louisiana to research and photograph unusual aspects of nature.