Zinnia Care 101: How to Grow Zinnias in a Home Garden - Bob Vila

By Amber Guetebier | Published Jul 21, 2022 9:52 AM
Photo: istockphoto.com
When it comes to pops of color in the garden bed, few flowers rival a hardy zinnia. Zinnias grow in a variety of colors and heights and love living in containers, making them the go-to summer annual for centuries.
Luckily, zinnia care is easier than you may think, and—with minimal effort—you will be rewarded with striking, long-lasting blooms that also make excellent cut flowers. This guide has the answers to questions you may have about how to grow zinnias.
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Common Name: Zinnia
Scientific Name: Zinnia elegans, Zinnia spp.
Hardiness Zone: Annual in USDA zones 2 through 8, perennial in zones 9 through 11
Soil: Rich, well-draining soil; pH 5.5 to 7.5
Light: Full sun
Water: Regular water
Food: Fertilize throughout the growing season
Propagation: Seed
Safety: Nontoxic
Photo: istockphoto.com
Most gardeners are familiar with the attractive annual zinnia variety Zinnia elegans. It’s easy to sprout from seed and grows prolifically in pots and garden beds alike. Hybrid colors range from snow white to pale green to delicate salmon; in fact, there are hybrids of Z. elegans in nearly every color of the rainbow! A stunning addition to any wildflower garden or window box, this species also comes in an array of flower forms, including single, semi-double, double, dahlia, globe, cactus, and even scabiosa, with the lattermost form named for its resemblance to the pincushion flower.
Other annual zinnia varieties are the compact Zinnia angustifolia and Z. haageana, or Mexican zinnia. The latter includes the Royal Horticultural Society’s award-winning cultivar ‘Aztec Orange’, which features gorgeous bright-orange double flowers. Another is Z. marylandica, a cross between Z. angustifolia and Z. elegans that is particularly mildew-tolerant, while Z. peruviana is native to the U.S. Southwest down through Argentina and sometimes called Z. pauciflora.
Perennial zinnia varieties include Zinnia grandiflora, otherwise referred to as prairie or Rocky Mountain zinnia, and Z. acerosa, also called desert zinnia. This low grower is native to the Rocky Mountains and Mexico and tolerant of colder winters in USDA zones 4 through 9. Meanwhile, Z. acerosa is native to Arizona, Texas, and Mexico. It is a ground cover with beautiful white flowers with yellow or sometimes purple florets at its center. These two native zinnias also attract hummingbirds, bees, and other pollinators in great numbers.
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Zinnias are low-maintenance ground covers once established and capable of providing months of dynamic color to garden beds and pots. Plant several varieties together to get big splashes of color in your zinnia garden with little effort.
Plant zinnias in the spring once the danger of frost has passed and daytime temperatures reach at least 50 degrees Fahrenheit. In areas with warmer springs, sow seeds directly in the ground. In cooler climates, start seeds indoors 4 to 6 weeks before the expected last frost date.
With a couple of exceptions, most zinnias are annual plants. Many are native to Mexico and the Southwest, so these flowers love heat. Plant them in a sunny spot in the garden where they’ll get at least 6 to 8 hours of sunlight a day. In areas with very hot summers, zinnias can tolerate partial sun. In areas with cool summers or fog, choose the sunniest possible spot, and avoid overhead watering of your growing zinnias to prevent powdery mildew formation.
Zinnias can tolerate a variety of soil conditions and heat once established, but give them the best possible start.
If starting from seed indoors:
If planting starts purchased at a nursery: Follow steps 5 through 7 above. Try to not disturb the roots of any native zinnias when transplanting new plants.
If sowing zinnia seeds directly in the ground:
Zinnias grow very well in containers, as long as they are regularly watered and do not become too rootbound. Be sure to use a potting mix—not heavy garden soil—to ensure adequate drainage. Look for smaller containers for Thumbelina zinnias.
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Although zinnias aren’t fussy overall, they are prone to powdery mildew, so water them with care. Soak the soil, not the plant. Give them regular water, watered at the soil level, and avoid overhead watering that gets leaves, stems, and flowers wet to avoid powdery mildew or sunburn. Also avoid overwatering zinnias, which can lead to wilting and rot. Note that native perennial varieties are extremely drought-tolerant once established.
Annual zinnias are considered heavy feeders. Give them plant food throughout the growing season; an all-purpose garden fertilizer works well, such as a 10-10-10. Apply it according to the directions on the fertilizer. Container plants may require more frequent fertilization. Consider fertilizing zinnias with a water-soluble plant food, but never apply it to dry soil.
Photo: istockphoto.com
Zinnia flowers tend to last for weeks, and sometimes for months at a time. Deadhead zinnia flowers when they start to look faded, and handpick damaged leaves. Native zinnias (Z. acerosa and Z. grandiflora) reseed and spread, so they only require shearing of faded leaves to reappear in late spring.
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Zinnias can be propagated from seed and grown directly in the ground or indoors 4 to 6 weeks before planting. They are relatively easy to grow from seed, and you can gather seeds from faded flowers if you like. Just beware that many varieties will not bloom true to seed, so to ensure their exact color and appearance, you are better off buying a new seed packet of that variety each year.
Propagating a zinnia from a stem cutting is more like a clone of the plant, but it requires some work. Choose a stem that is not flowering but has several sets of leaves, making a diagonal cut just below the lowest set. Then, remove the lower leaves and submerge the stem in warm water out of direct sunlight. Regularly change the water, and expect roots in about a week. Plant the rooted stem in a container filled with sterile potting mix or directly in the ground.
Photo: istockphoto.com
Zinnias are nontoxic to cats, dogs, and horses, as well as humans. Pollinators, including butterflies, bees, and hummingbirds, adore them.
Zinnias are prone to powdery mildew. To help prevent this, water only at the soil level and avoid getting leaves and stems wet. Do not water zinnias from overhead, and thin them as needed to give them air circulation. Occasionally, zinnias can be prone to leaf spot.
Overall, zinnias are resistant to many pests and diseases, but aphids, whiteflies, and spider mites will prey upon plants that may be stressed and under-watered during the hottest weather. Pay attention to watering on hot days to help prevent this stress. Hosing these pests off is usually enough to deter them. Zinnias are also deer- and rabbit-resistant.
Looking for more colorful flowers for garden beds and containers? Check out our guides on growing dahlia, hibiscus, and milkweed.
Disclosure: BobVila.com participates in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for publishers to earn fees by linking to Amazon.com and affiliated sites.
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