While gardening is generally an avocation requiring patience, this isn't the case with zinnias, one of the quickest flowers to bloom from seed. The huge range of flower colors, types, and sizes provides outstanding options for beds, borders, ground covers, containers, and cut flowers. Since I last wrote about them for this magazine 10 years ago, many new kinds of zinnias, including low-maintenance and disease-resistant types, have been introduced. These improvements may be just the impetus that brings these classic flowers, reminiscent of the roaring 1920s and country bouquets, into the gardens of a new generation.
Zinnias come in two main types: the large-flowered, upright, often tall garden kinds; and the small-flowered, low, often spreading kinds. Plants that result when these kinds are bred are called interspecific crosses.
Plants range from compact miniatures through medium-height bedding and border types to tall cutting types. The flowers, which are actually clusters of individual florets, come in single daisylike flowers, formally tailored doubles, cactus-flowered types with quilled rays, and anemone-flowered forms with broad rays around a cushioned center. Zinnia flowers, from nickel to Frisbee size, bloom in lavender, orange, pink, purple, red, rose, salmon, white, yellow, and even green.
Garden zinnia (Z. elegans) is the parent of dozens of beautiful but disease-susceptible varieties. These are famous for producing lavish displays of flowers, which come in many sizes. Plants range from 6 to 50 inches tall and have bristly oval leaves.
Choices include fully double flowers less than an inch wide on nearly 2-foot-tall varieties such as 'Lilliput Mix', or on miniature varieties such as 6- to 10-inch-tall 'Thumbelina Mix'. The 24- to 30-inch-tall 'Sunbow Mix' has 1-1/2- to 2-inch flowers. In the 2- to 3-inch flower range, you can choose among the 10-inch-tall Lollipop series, the 24- to 36-inch-tall Ruffles series, or flashy 24- to 30-inch-tall 'Envy' with unique single or double green flowers.
The large-flowered zinnias are the ones that capture most gardeners' fancies. For 5-inch-wide blooms on long stems, look for 30-inch-tall 'Giant-Flowered Mix' and the disease-tolerant 40- to 50-inch-tall Blue Point series. These big bloomers benefit from deadheading, weekly if possible, and may need staking for extra support.
Spreading zinnias (Z. angustifolia) have small, 1- to 2-inch-wide flowers, usually orange or yellow with dark centers, and slim, lance-shaped leaves. They resist common foliar diseases and tolerate heat and drought. Growing in loose mounds and reaching 8 to 18 inches tall, they can serve as annual ground covers, and are also attractive in hanging baskets or at the front of a border. Varieties include golden-orange 'Classic', 'Crystal White' (a 1997 All-America Selections winner), 'Star Gold', and 'Star Orange'.
Interspecific crosses are low-maintenance zinnias that have been introduced over the last decade. They combine the flower colors of garden zinnias with the durability of spreading zinnias.
The front-runner in this group is 'Rose Pinwheel', a mildew-resistant 1988 release with 3-1/2-inch single dusty rose flowers on tidy 12-inch-tall plants. The Pinwheel series now includes flowers in gold, orange, pink on white, and white.
In 1999, 'Profusion Cherry' and 'Profusion Orange' won the first All-America Selections Gold Medals awarded in a decade. Both bloom early and repeatedly, flowering in my garden just 45 days after planting three-week-old seedlings. They produced an abundance of 2-inch-wide flowers up until the first fall frost, long after other zinnias were finished. They grow about 15 inches tall, covering the old flowers with new leaves and buds, and thus eliminating the need to deadhead.
Unless given light afternoon shade, flowers of 'Profusion Cherry', which also won a Fleuroselect Gold Medal in European trials, tend to fade from a deep vibrant cherry to bleached cherry as they age -- a look some people like.
In containers, small- to medium-sized zinnias make a bright accompaniment to asparagus fern, ivy, variegated euonymus, licorice plant (Helichrysum petiolare), and petunias. Small zinnias make good edgers for summer annuals, filling in after spring pansies.
Medium-height zinnias blend beautifully into bright bedding schemes, mixing with daisy-flowered annuals such as cosmos and dahlias, or contrasting with spiky-flowered annuals such as salvia and larkspur. I particularly like 'Rose Border Beauty' with 'Purple Wave' petunias.
Tall zinnias are ideal for cutting and can be planted in clusters between perennials in a sunny, mixed bed. For instance, vivid orange-, red-, and yellow-flowered Mexican zinnias (Z. haageana) are good companions for sunflowers and black-eyed Susans. Brick red Z. peruviana 'Bonita Red' is a good match for purple coneflowers.
Where precise color coordination is important, look for seed packets with a single color of flowers. To find specific colors that best fit your planting scheme, you may have to scour catalogs for single colors of series such as Blue Point, Border Beauty, Oklahoma, Pinwheel, and Splendor. For a bright and busy multicolored bed in a kitchen or cutting garden, look for color mixes such as 'Oklahoma Formula Mix' and 'Sunbow Mix'.
Zinnias thrive in heat and grow anywhere that has several months of warm, frost-free weather. In humid regions or in northern areas, powdery mildew can be a problem, so plant disease-resistant varieties to allow extended bloom. In warm, long-season climates, a single planting may not last until the first fall frost, but successive sowing every couple of weeks through early July will provide fresh waves of flowers into fall.
Sow zinnias in the garden, or set out transplants. Seedlings, however, are notoriously poor transplanters. If the taproot is disturbed, the flowers may revert to single forms, a big disappointment if you have your heart set on large doubles. "Green" seedlings -- not yet in bloom and still in oversized containers -- generally make the transition best.
Direct-sown plants catch up so quickly to transplants that you can hardly tell the difference. Plant zinnias in well-drained soil. Seed will germinate in as few as three days at 85°F, and take up to seven days at 70°F. Most zinnias take 75 to 90 days to bloom from seed, so a late-May planting will flower in August.
To encourage quick growth and best performance, amend soil with compost before planting. Most zinnias thrive in full sun, particularly in cool climates, but in hot climates they may benefit from light afternoon shade.
Space smaller varieties as close as 6 inches apart, intermediate ones about 12 inches, and tall kinds up to 18 inches. Where foliar diseases are a problem, allow extra space; good air circulation can discourage diseases. During dry weather, water with a soaker hose or drip irrigation to avoid wetting the foliage.
If growth is slow or leaves look pale green, fertilize with a soluble or controlled-release fertilizer. Choose a formulation with modest or low nitrogen so that excessively tall growth is not forced, and follow label directions.
Cut flowers can last a week or more. Harvest the flowers when they are fresh but fully mature, ideally when pollen begins to form. Take a bucket filled with water out into the garden, submerging the cut stems immediately, then recut the stems underwater before using them in arrangements. To double the vase life, add a commercial cut-flower preservative, or a teaspoon of bleach and sugar to the water.
Mildew is the primary zinnia troublemaker. It can attack susceptible kinds, which include most garden zinnias, whenever the weather is warm and rainy or humid. In cool climates, it often attacks in late summer or fall when cool nights cause moisture to condense on the foliage, an invitation for the spores to attack. They penetrate the leaves, drawing out moisture and leaving a dusting of thousands of powdery white spores that spread to other zinnias. Plants are quickly disfigured, and death often follows. To avoid problems, grow resistant series such as Blue Point, Pinwheel, and Profusion.
You can slow the spread of mildew on susceptible zinnias by spraying a protective coating of a baking soda solution (1/2 teaspoon baking soda in 2 quarts of water with a few drops of liquid soap).
Insect pests are rarely a problem, but you may find Japanese beetles, mites, and aphids. Drop the beetles into soapy water, and treat mites and aphids with insecticidal soap.
Recommending varieties can be tricky, because new zinnias regularly replace older ones, but I can't resist sharing the names of my current favorites. The largest group, the garden zinnias, are listed first. They are grouped by height and ranked from shortest to tallest. Other kinds of zinnias follow, alphabetically by species name, and are similarly listed by height.
Prices vary widely, so check several catalogs. For instance, seeds of the Profusion series cost about 6 cents each in one catalog and nearly twice as much in another.
Also note the difference between a mix and a formula mix. A mix contains a mixture of seeds in random proportions; a formula mix is designed to produce a nearly equal number of each color.
1. Garden zinnias (Z. elegans).
Low-growing (less than 20 inches tall).
Medium height (20 to 30 inches tall)
Tall (over 30 inches tall)
2. Other Zinnias
Z. acerosa (syn. Z. pumila)
Z. haageana (syn. Z. mexicana)
Z. peruviana (syn. Z. pauciflora)
3. Interspecific Hybrids
Susan McClure is the author of numerous gardening books and articles. In 1999, she published The Free-Spirited Garden (Chronicle Books, $19).
Photography by Suzanne DeJohn/National Gardening Association
Article published on June 23, 2008.