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Zinnias: How to Plant, Grow, and Care for Zinnia FlowersZinnias: How to Plant, Grow, and Care for Zinnia Flowers
The OG Test Garden has many attractions at the end of the season. A dozen or so new tomato varieties are ripe and ready for us to taste. Sunflowers are raising up their shining faces. The scent of licorice wafts from the anise hyssop. Goldfinches dart in to snatch seeds from flowers finished blooming and tiger swallowtail butterflies alight for a sip from blossoms still at their peak. And most days the sun rises gloriously through the mist that overnight has given every plant a fresh sheen.
Among all of these extraordinary delights, however, a very familiar flower always sparks oohs and aahs of admiration, from veteran horticulturists and casual passersby alike. The zinnias planted solely to brighten up our garden never fail to cheer us with their brilliant blossoms that open continuously from midsummer all the way to the first hard frost. Just look at the photographs on these pages, shot at our garden here in eastern Pennsylvania, and you’ll see that zinnias embody the simple beauty of an organic garden at its peak. But zinnias earn their place in our garden (and hearts) for more than their good looks.
You, too, will love growing zinnias because of all they have to offer:
1. A rainbow of color options. They come in every eye-catching hue except true blue, so you can match them with your favorite perennial or annual flowers, foliage plants, and herbs.
2. A height for every site. Want tall, back-of-the-border plants with huge, dahlia-like blossoms? Need a low-growing flower with simple yet colorful petals? Zinnias fill the bill in both cases and in so many other situations.
3. No fuss, big payoff. If there’s a flower that’s less demanding of your time and attention than zinnias, please tell us, because we need to know about it.
4. A banquet for birds and butterflies. Plant a patch of zinnias and watch your yard come to life with the entertaining activity of wildlife on the wing.
5. Never-ending bouquets. The more blooms you snip from zinnias, the more they produce. Every week, you’ll get a fresh bouquet that no florist could match.
Of course, we could go on about our love of zinnias, but we’ll let the pictures speak for themselves. After you’ve looked at them, come back here to find out how to grow them yourself.
Start from Seed
Where spring warms up early, wait until the last frost has passed before directly sowing zinnia seeds outside. Plant the seeds only about a ¼ inch deep. You’ll see seedlings sprout in four to seven days. Once the seedlings reach about 3 inches tall, thin them so that they’re 6 to 18 inches apart to maximize air circulation (a key to keeping zinnias looking good all season).
In cooler climates, start seeds indoors four to six weeks before your area’s average last frost date. Harden off the plants by vacationing trays outside for a few hours per day before planting them in your garden.
If you buy zinnia plants at the garden center that have already reached flowering size, ease the transition to your garden by pruning the plants back by one-third. Then sit back and watch your zinnia patch mature and flourish!
We’re ready to guarantee that zinnias will not fail you. But if you live where late summer nights are cool and humid, brace yourself for a potential encounter with powdery mildew. Prevention is your best defense against this troublesome fungus, says Larry Hodgson, author of Annuals for Every Purpose. He recommends protecting zinnias from the grayish white growth by maintaining good air circulation around them, watering at the roots, and choosing mildew-resistant varieties (see “5 Top Choices” for specific recommendations). Last summer, Japanese beetles clustered on the zinnias growing in the OG Test Garden. However, our research editor and garden manager, Pam Ruch, observed that the beetles flocked more to the lime and white zinnias and were less attracted to bright orange, red, and purple varieties. If you live where these beetles are a pest, simply hand-pluck the marauders off the foliage and drop them into a bucket of soapy water.
5 Top Choices
Every year, a fresh crop of new zinnia varieties are touted as the best yet. We’ve grown many of them and have waded through the riot of pinks, yellows, oranges, and reds to compile this hit parade.
If you want big, bright, and bold flowers, you’ll love ‘Benary’s Giant’ (Zinnia elegans). Even in the saturated air of a Pennsylvania July, these Goliaths remain mildew free. They sometimes tire of standing perfectly straight as the summer draws to an end. That’s why some gardeners start the second flat of seedlings in June and transplant it in mid-July. The result? Clean, fresh, upright blooms from August until frost.
You’ll find plenty of midheight zinnias to choose from, including candy-cane-striped heirlooms and ‘Cut and Come Again’ mixes. Just when you think you’ve settled on a favorite, along comes a new look that totally knocks your clogs off. This year the newcomer was ‘Zowie! Gold Flame’. Not towering, but not cowering either, it grows to a robust 30 inches tall, in an in-your-face blend of red and gold. Interesting up close and eye-catching from a distance, the effect is like a mass of French marigolds on steroids. And it wasn’t just us that liked them—the butterflies preferred them over all other varieties. Nice in a blue vase.
Many zinnia varieties have passed the rigorous testing needed to earn an All-America Selections award. But the only series to win the coveted AAS Gold Medal was the hybrid Profusion Series. The neatly mounded shape, consistent color, and disease and drought tolerance of ‘Profusion’ zinnias have won over researchers, landscapers, and home gardeners. Unlike most zinnias, which are sold in multicolored mixes, ‘Profusion’ is available in single colors: Orange, Cherry, and White. Highly useful to those who like to color-plan their gardens. Look for new colors in the world.
For a zinnia with a different look that resists powdery mildew valiantly, try growing the narrow-leaved Z. Angustifolia. It’s sold in the Star Series or the Crystal Series and is trouble-free, drought-tolerant, and a perfect size (about 1 foot tall and wide) for the front of the border. We find it to be very companionable—in party terms, “a good mixer.” Stealthily slip young plants into the gaps left by May tulips and perennials that aren’t as perennial as you thought they were—these varieties have a way of making everything around them look better.
Varieties such as ‘Old Mexico’ and ‘Persian Carpet’ are two excellent members of the Z. haageana species. They have a rough-and-tumble habit, and the rich golds, reds, and copper colors foreshadow the coming of fall. ‘Old Mexico’ bears mostly double flowers (two layers of petals rather than one), while ‘Persian Carpet’ produces 2-inch double and semidouble blooms in bold autumnal shades.
The two alternative species of zinnia just mentioned—Z. angustifolia and Z. haageana—have a naturally strong resistance to powdery mildew. Breeders have preserved this trait in series like Profusion and Pinwheel, making these modern hybrids especially appealing to us organic gardeners, who strongly prefer prevention to treat a problem.
Save for a Bright Future
You might think that seed saving is a complex challenge best left to advanced gardeners. Not true when you’re talking about zinnias. It could not be easier, and when you save seeds, you not only get the colors you want (and only the ones you want), but you can also select seeds from the healthiest plants. Do this, and in a couple of generations of seeds, you will have developed your own strain of zinnias selected to perform well in your conditions.
Right now, in early fall, is the time to give this a try. Get a few envelopes and a pencil—don’t forget the pencil because trust us, you will not remember what is in the envelope. Simply clip off a dried flower head from each color that you want to save. Pull the flower apart and remove the seeds inside, or simply put the whole blossom in the envelope. Seal and identify the color. Keep it in a cool, dry place until it is time to plant next year. That’s all there is to it. Now you are a seed saver!
If there’s one thing that’s better than a hearty border of cheerful zinnias, it is a plot of zinnias accompanied by a partner that shows them off to their best advantage. Try these winning combinations:
- ‘Benary’s Giant Lime’ and Verbena bonariensis
- ‘Big Tetra Mix’ and Alternanthera ‘Purple Knight’
- ‘Cut and Come Again’ in mixed colors and red fountain grass (Pennisetum setaceum ‘Rubrum’)
- ‘Persian Carpet’ and ‘Blue Horizon’ ageratum
- ‘Profusion Orange’ and Salvia farinacea ‘Victoria’
- ‘Star White’ and black-eyed Susans
- ‘Zowie! Gold Flame’ and ‘Purple Majesty’ millet
What do you know about zinnias?
The zinnia got its name from 18th-century German botanist Johann Gottfried Zinn, who wrote the flower’s first scientific description.
Zinnias are native to Mexico, where Aztecs originally dubbed these flowers mal de Ojos (“hard on the eyes”).
When zinnias were introduced to Europeans, the flowers were referred to as “poorhouse flower” and “everybody’s flower” because they were so common and easy to grow.
Dwarf zinnias can be as short as 10 inches tall; the giants reach up to 4 feet.
Zinnias were once popularly called “youth and old age” because old blooms stay fresh as new blooms open.
The luminous ‘Magellan Coral’ zinnia was honored as a 2005 All-America Selections Winner.
From 1931 to 1957, the zinnia was Indiana’s state flower. (It was replaced by the peony.)—L.S.