Zinnias are certainly among the easiest flowers for anyone, whether just beginning or experienced in gardening, to germinate and grow directly from seed. Their easy culture, heat tolerance and colorful mid to late summer show, blooming hard when other annuals are spent, make them well worth exploring. Zinnias make superb long-stemmed cutting flowers with long-lasting blooms. I love planting bright zinnias mixes near other later summer flowers like amaranth, sunflowers, and tithonia, and if you have zinnias, you will be inviting butterflies to visit your garden!
Zinnias elegans is the well-known species with the most modern cultivars in a wide variety of plant heights, flower sizes, flower forms and colors. As these vibrant flowers mature, their center discs open into a circle of tiny golden stars. Today, thanks to active breeders, there is just about every imaginable flower form: dahlia-flowered, quilled, crested, ball or pompon-like, single, semi double, fully double. Z. elegans come in every color and some bi-colors except true blue. Color choices are so broad that you can choose from all the way from deep, intensely bright shades to soft, creamy pastels and white. Bi-Colors and striped and speckled varieties are also available. Heights range from 8 inches to almost 4 feet tall. Zinnias Elegans have also been hybridized to increase their resistance to disease and give more weather tolerance.
Zinnia elegans – dahlia flowered:
'Benary's Giants' (Blue Point) are the #1 florist choice for cut flowers. Bred and introduced by the Dutch about 10 years ago, these garden beauties have long, strong stems on multi-branching plants that reach 3 to 4 feet tall. Flowers are fully double with densely filled petals that look almost beaded and are available in 12 sparking colors. They have better mildew resistance than older large dahlia-flowered mixes, are especially attractive to butterflies, and make beautiful in bouquets. These are available in many single colors such as Apricot Blush, and also in custom blends such as Hot Crayon Colors which combines bright yellow, citrus orange and rich red; Cool Crayon Colors, which combines lavender, carmine-rose, soft pink and white; Décor, which blends apricot blush with unusual, vivid chartreuse; or Berry Basket, with grape, pink, rose and raspberry shades.
'Envy' zinnia variety belongs in every flower arranger's garden. It's vivid unusual chartreuse color sets off brighter summer flowers and harmonizes equally well with soft pastels. The old heirloom cultivar did not have good color or reliable flower form, but the 'Benary's Giant' selection called Green Envy is much improved with truly double, many petaled green flowers on long branching stems.
'Pumila' or Cut And Come Again – this old favorite's name reflects its almost continuous bloom for several months. Fully double and semi double, 2 to 3 inch flowers. This well- branched heirloom variety has been exceptional color range including many pastels. Plants reach about 3-31/2 feet tall. While they are not particularly disease resistant, these old-fashioned zinnias have a lovely rounded blossom form and many stems for cutting.
Zinnia elegans – cactus flowered:
Tall, 3-4 foot cactus flower zinnias have semi double,4 to 6 inch, slightly curved and twisted petals making them resemble quilled chrysanthemums. They usually come in mixes of bright colors including canary yellow, golden, orange, crimson, scarlet, apricot, coral, carmine, lilac, rose, pink and white.
Raggedy Anne is an exuberant mix of these old-fashioned large quilled flowers in radiant shades that make especially nice bouquets.
This more diminutive species is most often available as a bi-color mix. The oldest heirloom variety is Persian Carpet, a mix of many singles, semi doubles and doubles. It comes in a mosaic of chestnut, mahogany, bronze, orange, and rust, with contrasting circles or picotee edges of yellow and cream that create a rich tapestry of color. These lovely flowers are multi-branching and low growing, reaching 12- 18 inches tall and make charming little bouquets.
Zinnias need warmth to germinate and grow easily. To start early indoors: In cold-weather climates, you can get a head start on the season by starting zinnias from seed indoors four to five weeks before the last spring frost date. Sow seeds 1/2" deep and 3 inches apart in a container of moist but not soggy seed starting mix. Keep warm and moist, fertilize with half strength liquid fertilizer every 10 days and provide a strong light source until seedlings are ready to plant outside when spring night temperatures rise above 50° both day and night.
To start directly in the garden: In both cold and mild winter climates, wait until when all danger of frost has passed, days and nights are evenly on the 50-55° range and weather is warm and settled. Remember: if is too cold, zinnias simply won't germinate or tender seedlings may suffer from damping off and die, so it's just not worth trying to start them too early. In the right conditions, seeds germinate quickly and once seedlings are up and well established, they will grow rapidly and bloom abundantly all across the country.
Sow seeds in well worked, fertile garden soil in full sun. Space seeds 2 to 3 inches apart in rows 12 inches apart. Cover 1/2" deep and gently firm soil. Keep soil evenly moist while awaiting germination which takes five to 10 days. When seedlings are large enough to handle, thin to stand 10 -12 inches apart; adequate spacing gives plants room to grow and provides the good air circulation zinnias need to keep plants productive and disease free and producing an abundance of flowers. If you live in an area with long summers that don't get too humid, you can plant zinnias in the spring for summer flowers and then sow again at midsummer for bountiful fall blooms.
Cut flowers as blossoms first begin to open and petals are tight for longest vase life. Cut flowers often to enjoy lavish bouquets indoors and give away as gifts because the more flowers you cut, the more the plants will produce for a long season of bloom. Feed plants with a good well-balanced flower fertilizer every few weeks for best flower production and keep evenly watered. Cut long stems well back into the plant, to keep plants branching low and producing the best blooms. Strip off the leaves so flowers last longer in a vase. A good floral preservative can increase vase life for cut zinnias.
One of the most common diseases to afflict zinnias is powdery mildew, especially in hot areas with humid summers. If this is a serious problem, plant the most disease resistant varieties (the new hybrids are especially good here) and be scrupulous about providing full sun, adequate spacing and air circulation between plants. Avoid overhead watering if at all possible. The powdery mildew fungus begins to show up in zinnia plantings during late summer. One favorite remedy is to use one tablespoon of baking soda to one gallon of water and spray it directly on the leaves and other parts of the affected plant. Weekly spraying thereafter should provide control. In very wet weather, viral diseases can be a problem. If only the leaves are discolored, remove them when cutting so you can still enjoy the flowers in a vase. Protect young seedlings from slugs and snails by using one of the new nontoxic controls. If marauding birds, find young seedlings attractive, use bird netting until seedlings are four to 5 inches tall.