How to Grow Zinnia -- Garden Chronicle

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Zinnia is a low, bushy annual with oval dark green leaves, and red, yellow, purple, pink, and sometimes green daisy-like flowers from summer to early fall. Zinnias offer masses of color in beds and borders and can be grown in small groups in containers and pots.

Zinnias are hot-weather plants. They do best after the weather warms in late spring or early summer. When autumn comes, zinnias can suffer from powdery mildew as nights grow longer and dew sits on plants longer.

Most garden zinnia belongs to the species Zinnia elegant.

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Table of Contents

Get to know Zinnia

Plant type: Annual
Growing Zones and range: Annual in all zones
Hardiness: Tender
Height and width: 12 to 24 inches (30-61cm) tall; 6 to 15 inches (15-38cm) wide
Foliage: Leaves range from linear to ovate or rounded
Flowers: Showy daisylike flowers can be single or double; the flowerheads of some resemble formal decorative dahlias (referred to as “dahlia-flowered”), others resemble cactus-flowered dahlias (referred to as “cactus-flowered”)
Flower colors: Shades of orange, red, bronze, hot pink, orange-red, and yellow-orange as well as white, pale pink, cream, and green
Bloom time: Summer to frost
Uses: Cut flowers, beds, borders; compact hybrids; taller varieties for cutting; containers; zinnias attract hummingbirds and butterflies
Common name: Zinnia
Botanical name: Zinnia spp.
Family: Asteraceae
Origin: Primarily Mexico, also southwestern North America, and parts of Central and South America

Where to plant Zinnia

Plant zinnias in full sun in Zones 2-8. Plant zinnias in light shade in hot-summer regions in Zones 9-11.
Grow zinnias in humus-rich, well-drained, neutral to acidic soil.
Planting zinnias where there is good air circulation will stem attacks by pests and diseases.

Zinnia uses

Use Zinnias in annual or mixed borders and for cutting.
Use Zinnias to edge beds and borders and along walkways.
Some cultivars are suitable for window boxes or other containers.

When to plant Zinnia

Set zinnias in the garden in spring after all danger of frost has passed.
Sow seeds indoors 6 to 8 weeks before the last frost; sow seeds at 60° to 65°F (15.6-18°C).
Transplant zinnias to the garden with care a week or two after the last frost in spring.
For season-long blooms, sow seeds every 3 to 4 weeks until mid-summer.

Planting and spacing Zinnia

Space zinnias 6 to 15 inches (15-38cm) apart depending on the variety.
Sow seed 1/4 inch deep in sterile seed starting mix indoors; sow seed outdoors in evenly prepared garden soil.

How to water and feed Zinnia

Zinnias need moderate moisture; keep the soil evenly moist.
Fertilize zinnias occasionally every 4 to 6 weeks with an all-purpose fertilizer.
Zinnias are prone to mildew; avoid wetting leaves and select mildew-resistant varieties.

Zinnia care

Mulch around zinnias to conserve moisture and stem the spread of disease in splashing water.
Pinch the ends of growing tips to encourage fuller plants. Do not pinch plants if you are growing zinnias for cut flowers and want long-stemmed flowers.
Stake tall plants as needed.

Zinnia pests and diseases

Aphids, capsid bugs, chrysanthemum eelworms, and earwigs may attack zinnias.
Seedlings are susceptible to damping off and in wet conditions fungal root rots.
Grey mold may infect the flowers in wet seasons.
Powdery mildew can settle on leaves in cool or wet weather.

Zinnia elegans Whirligig strain — *Zinnia elegans* Whirligig strain

Zinnia propagation

Zinnia seeds germinate in 7 to 10 days at 70° to 80°F (21°-27°C).
Sow seeds indoors or in a greenhouse in spring 6 weeks before transplanting them to the garden.
Sow seed outdoors after the last frost in spring; sow seed in final planting position and thin out the seedling to the required spacing.
Zinnias do not like roots being disturbed at transplant time.

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Zinnia elegans Dahlia-flowered strain — *Zinnia elegans* Dahlia-flowered strain

Zinnia varieties to grow

Zinnia angustifolia: Annual, compact plants to 16 inches (40cm) tall; inch-wide flower hears; bloom in 6 weeks from seed; perennial in mild winter; can be used in hanging baskets.
Z. elegans: Annual grows 12 to 36 inches (30-91cm) tall; flower heads from 1 to 7 inches (2.5-17cm) across; forms include full doubles, cactus flowered, and crested; colors in white, pink, salmon, rose, red, yellow, orange, lavender, purple, and green; strains include Border Beauty, Burpeeana California Giants, Ruffles, State Fair, Zenith.
Z. grandiflora: Perennial in warm-winter regions, grows to 10 inches tall, flowerheads 1.5 inches across.
Z. haageana: Annual, compact plants to 18 inches (45cm) tall, flowers in red, yellow, and orange, long-blooming.

Zinnia angustifolia (Z. linearis) — Narrow-leaf zinnia

Narrow-leaf zinnia is a short, sprawling plant with 1-to 2 ½-inches-wide single blossoms in burnished yellow, orange, or white, with prominent orange centers. Narrow-leaf zinnia blooms freely all summer, blanketing the narrow dark green leaves with brilliant color.

Size: Grows to 1 foot tall; sprawling.
Light: Full sun; part sun in hottest areas.
Soil and moisture: Moderately fertile, nonalkaline, well-drained soil; best with regular moisture although drought tolerant.
Planting and propagation: Best sown in the garden after the last frost. Sow indoors in peat post, at 75° to 80°F, six weeks earlier. Set 6 inches to 1 foot apart.
Special care: Avoid wetting leaves. Needs no deadheading.
Pest and diseases: Sometimes mildew.
Climate: Warm-season annual in zones 2-11; thrives in heat.
Cultivars: ‘Star’ series: ‘Orange’; ‘White’; ‘Starbright Mix,’ orange, white, and gold; ‘Classic Orange,’ orange; ‘Classic White,’ creamy white.
Garden use: Easy-care plant for informal gardens, cottage gardens, and containers.

Zinnia elegant — Common zinnia

Zinnia elegant is a sturdy plant that bears bright flowers from early summer to frost. Plants and flowers vary from dwarf to tall, with blossoms from 1 to 6 inches across. Most flower are double but there are also pompons or cactus types. Blossoms include colors of the rainbow, in brilliant hues and pastels. Some types are bicolored, streaked, and speckled with other colors.

Size: 6 inches to 3 feet tall. Some bushy; others upright and narrow.
Light: Full sun; part sun in hottest areas.
Soil and moisture: Fertile, well-drained soil; water regularly.
Planting and propagation: Best sown in the garden after the last frost. Sow inside in peat pots, at 75° to 80°F, six weeks earlier. Set 6 inches to 1 foot apart.
Special care: Avoid wetting leaves. Cut often to encourage blooming. Strip off leaves before adding to arrangements.
Pest and diseases: Mildew-prone, although many cultivars are now mildew-resistant; bacterial wilt, alternaria, powdery mildew, root and stem rot, Japanese beetle, and mites may be troublesome.
Climate: Warm-season annual in zones 2-11.
Cultivars: ‘Thumbelina,’ 6 to 10 inches tall, 1 ½- to 2-inch flowers; ‘Peter Pan,’ 10 inches to 1 foot tall, 4-inch flowers, ‘Splendor,’ 22 inches tall, 5-inch flowers; ‘Peppermint Stick Mix,’ 2 feet tall, streaked bicolors; ‘Cut and Come Again,’ 2 feet tall; well-branched, ‘Dreamland’ series: 4-inch flowers in bright colors, compact, 10 inches to 1 foot tall.
Garden use: Plant in masses in the foreground or mid-ground of borders, cottage gardens, and cutting beds.