How to Grow Zinnia -- Garden Chronicle (2024)

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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How to Grow Zinnia -- Garden Chronicle (2)

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
How to Grow Zinnia -- Garden Chronicle (3)

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.
How to Grow Zinnia -- Garden Chronicle (4)

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 Grow Zinnia -- Garden Chronicle (5)

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.
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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 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.
How to Grow Zinnia -- Garden Chronicle (2024)

FAQs

How do you grow zinnias successfully? ›

Even though zinnias can tolerate short periods of drought, Mbofung-Curtis says they'll grow best in moist soil. "Water plants about three times a week so that the soil stays moist to about 6 to 8 inches deep," she advises. For potted plants, she recommends only watering them when the soil feels dry.

What is the best fertilizer for zinnias? ›

Plantings should be fertilized at least twice during the growing season using a balanced granular or water soluble 20-20-20 fertilizer or a slow release fertilizer at the time of planting. Give each plant plenty of space when setting them out as the hairy stems of zinnias are susceptible to powdery mildew.

What month do you plant zinnias? ›

You can plant your seeds in late March and April. Consider planting them in stages for more continual bloom. Zinnias prefer well-drained soils with a pH range of 5.5 to 7.5. They benefit from soil that is organically enriched.

Where is the best place to plant zinnias? ›

Light: Zinnias grow and flower best in full sun. They can flower in part shade, especially in warmer climates with afternoon shade, but they may be more susceptible to disease and have fewer flowers. Soil: Zinnias grow best on fertile, well-drained soils high in organic matter.

Do zinnias do better in pots or in the ground? ›

Zinnias are vibrant and colorful flowers that add beauty to any garden. If you have limited space or lack a traditional garden bed, growing zinnias in pots is an excellent alternative.

Is Epsom salt good for zinnias? ›

Feed plants with nitrate-based fertilizer at 200- to 250-ppm nitrogen. Interveinal chlorosis may indicate magnesium deficiency; supplement with MgSO4 (Epsom Salts) at 16 ounces/100 gallons. If grown on the lean side and too dry, zinnias may flower prematurely.

Can I use Miracle Grow on zinnias? ›

The secret to growing the biggest, greenest zinnias is to fertilize them! I can't underestimate what a huge difference this makes. The zinnias on the left were fertilized several times with Miracle Grow- what a huge difference!

Should I water zinnias everyday? ›

Zinnias prefer consistent moisture but don't like to be over-watered. Water them deeply once or twice a week, depending on your local climate. Avoid overhead watering to prevent leaf diseases.

Can I just scatter zinnia seeds? ›

Can I just Scatter Zinnia Seeds? I love that zinnia seeds can be scattered or evenly placed in your soil. It is recommended that they be planted ¼ inch deep in moist soil. Most packets say that you space seeds about 6 inches apart, with rows at least 12 inches apart.

How deep to plant zinnias? ›

Plant the seeds only about ¼” – ½” deep and you should see seedlings sprout in four to seven days. Once the seedlings reach about 3” tall, thin them to maximize air circulation, and prevent powdery mildew.

Do zinnias like to be crowded? ›

Thin seedlings: Once the zinnia seedlings have grown their first true leaves, thin them to about 6-18 inches apart (15-45 cm) to give them room to grow. Don't crowd zinnias to keep them disease-free and avoid powdery mildew. Air circulation is important.

What do overwatered zinnias look like? ›

Overwatering can turn your zinnias into a soggy mess, leading to droopy leaves and the dreaded root rot. It's like giving your plants a bath when they just need a quick shower. Check the soil; if it's wetter than a rainforest floor, hold off on the H2O.

Why do farmers plant zinnias? ›

Zinnias are easy to grow

They're a flower that pretty much anyone can grow and can thrive in just about any adverse environment - dry, hot, humid, high wind - and grow vigorously and prodigiously. They can be started in trays or seed blocks, or can be direct sown in the ground, and will do quite well.

Do zinnias come back every year? ›

Zinnias are annuals in most areas of the country that have four seasons, including a cold winter. This means they last for one season. If you want zinnias every year, you will have to replant every spring. Zinnias are not cold tolerant, so check your last freeze date for your growing zone.

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