Zinnia: Plant Care and Growing Guide

When to Plant Zinnias

• Zinnias are warm-season annual flowers that are planted in the spring after the last frost date in your area. The exact planting time will vary depending on your location, but generally, zinnias should be planted when soil temperatures have reached at least 60°F (15.5°C). In most areas, this will be in late spring or early summer.
• It’s important to note that zinnias don’t tolerate frost, so make sure to wait until all chance of frost has passed before planting them outdoors. In areas with a long growing season, you may also consider planting a second crop of zinnias in mid-summer for an extended bloom period.
• If you prefer to start zinnias indoors from seed, you can begin sowing the seeds 4-6 weeks before the last expected frost date in your area. This will give the seedlings a head start and allow you to transplant them outdoors once the weather has warmed up.

Where to Plant Zinnia Flowers

Sunlight: Zinnias prefer full sun. They can tolerate some light shade but will not bloom as well in areas with less than 6 hours of direct sunlight per day.

Soil: Zinnias thrive in well-draining soil that is rich in organic matter

Water: Zinnias are fairly drought-tolerant but will do best with regular watering during dry periods.

Climate: Zinnias are warm-season annuals that thrive in hot and sunny weather.

Placement: Zinnias are versatile and can be planted in a variety of locations in the garden. Some popular locations to plant zinnias in the garden include:

Flower beds: Plant zinnias in flower beds to create a colorful display of flowers. They can be planted in rows or clusters to create a variety of patterns and designs.

Borders: Use zinnias to create a border around a garden bed or along a pathway. They come in a range of colors, which can be used to create a specific color scheme.

Containers: Zinnias can be grown in containers and placed on a deck or patio. Use a good-quality potting mix and make sure the container has good drainage.

Cutting gardens: Zinnias are unsurpassed as cut flowers and can be planted in a dedicated cutting garden. Plant them in rows or clusters to create an abundant supply of flowers for cutting.

How to Plant Zinnias

Here are some steps to grow zinnias:

• Choose a sunny location: Zinnias need at least 6 hours of direct sunlight daily.
• Prepare the soil: Zinnias grow best in well-draining soil. Amend the soil with compost or organic matter if necessary.
• Plant the seeds: Zinnia seeds can be sown directly into the ground after the danger of frost has passed or started indoors 4-6 weeks before the last frost. Plant the seeds 1/4 inch deep and 4-6 inches apart (See back of seed packet for variety-specific advice.). Water gently.
• Germination: Zinnia seeds typically germinate within 5 to 10 days after planting, although the exact time may vary depending on factors such as soil temperature, moisture, and seed quality.
• 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.

By following these steps, you can grow healthy and vibrant zinnias in your garden.

How to Care for Zinnia Flowers

Here are some tips for caring for zinnia flowers:

• Watering: Zinnias prefer well-drained soil and require regular watering, especially during dry spells. Water the plants deeply once a week rather than giving them frequent light watering.
• Fertilization: Zinnias will benefit from occasional fertilization with a balanced fertilizer.
• Deadheading: Removing spent flowers promotes continuous blooming and prevents the plant from going to seed too quickly.
• Pruning: Pinch back the tips of young plants to encourage bushiness and more flowers.
• Mulching: Apply a layer of organic mulch around the base of the plants to help retain moisture and suppress weeds.
• Staking: Tall zinnia varieties may require staking to prevent the stems from breaking in strong winds.

By following these care tips, you can enjoy healthy and beautiful zinnia flowers all season long.

How to Propagate

Zinnias can be propagated through seeds, cuttings, or root division.

Seed propagation:

• Sow the seeds indoors 4-6 weeks before the last frost or directly outdoors once the soil has warmed up in the spring.
• Choose a sunny spot and prepare the soil by adding compost or organic matter to improve drainage.
• Sow the seeds about ¼ inch deep and water gently.
• Keep the soil moist and warm, and the seeds should germinate in 5-10 days.
• Once the seedlings have grown a few inches tall, thin them out to about 6-18 inches apart (15-45 cm).

Cutting propagation:

• Take a cutting from a healthy zinnia plant by cutting a stem that is about 4-6 inches long (10-15 cm).
• Remove the leaves from the bottom half of the stem.
• Dip the cut end of the stem in rooting hormone powder.
• Plant the cutting in a container filled with a mixture of soil and perlite.
• Water the cutting and cover the container with a plastic bag to create a humid environment.
• Keep the soil moist and place the container in a warm, bright spot without direct sunlight.
• The cutting should develop roots in a few weeks and can then be transplanted into a larger pot or directly into the garden.

Root Division:

• Dig up the entire plant, taking care not to damage the roots.
• Gently shake off the excess soil and separate the roots into several sections.
• Trim off any damaged or dead roots with a clean pair of scissors or pruning shears.
• Replant each section in a pot or directly in the garden, making sure that the soil is moist and well-drained.
• Water the newly planted sections thoroughly and place them in a location with plenty of sunlight.
• Keep the soil moist and continue to water the plants regularly until they become established.

Pests and Diseases

Zinnias are generally not very susceptible to pests and diseases, but they can occasionally be affected by a few problems.

Bacterial leaf spot: This is a bacterial disease that causes brown spots on the leaves of the plant. It can be prevented by avoiding overhead watering and removing infected leaves.

Bacterial wilt: This bacterial disease cause zinnia plants to wilt and die. Symptoms include wilting and yellowing of leaves. The disease can spread quickly in warm, humid conditions, so it’s important to remove infected plants and avoid overwatering.

Cutworms: These larvae of certain species of moths and beetles feed on the stems of young plants, often cutting them off at the soil level.

Mealybugs: These small insects are usually found on the undersides of leaves, in leaf axils, and at the base of the plant. They can cause stunted growth, yellowing of leaves, and a sticky substance called honeydew on the leaves.

Powdery mildew: This is a fungal disease that appears as a white, powdery coating on the leaves and stems of the plant. It can be prevented by providing good air circulation and avoiding overhead watering.

Spider mites: These tiny pests can cause yellowing and stippling of the leaves. They can be controlled with insecticidal soap or horticultural oil.

Companion Plants for Zinnia

Zinnias are beautiful, colorful flowers that can be complemented by a variety of companion plants. Some of the best companion plants for zinnias include:

Marigolds: These cheerful flowers complement zinnias well and also repel many insect pests.

Cosmos: These daisy-like flowers come in a range of colors and heights, making them a great choice to grow alongside zinnias.

Nasturtiums: These bright, edible flowers have a peppery flavor and add a splash of color to any garden.

Salvia: This flowering plant attracts pollinators and comes in a variety of colors that complement zinnias.

Ageratum: This annual plant produces clusters of blue, pink, or white flowers that complement zinnias well.

Cleome: These tall, spiky flowers come in a range of colors and add height and interest to a zinnia garden.

Dahlias: These showy flowers come in a range of colors and sizes, and their height and texture make them a great complement to zinnias.

Verbena: This low-growing plant produces clusters of flowers in a range of colors that complement zinnias well.

Sunflowers: These tall, striking flowers add height and texture to a zinnia garden and attract pollinators.

Lantana: This hardy, drought-tolerant plant produces clusters of flowers in a range of colors that complement zinnias well.

Overall, choosing companion plants with similar growing requirements and complement the colors and textures of zinnias can help create a beautiful and thriving garden.

Click here to compare all Zinnia varieties

Frequently Asked Questions

How long will zinnias bloom?

Zinnias are known for their long blooming period, which can last from early summer until the first frost. With proper care and deadheading, zinnias can continue to bloom for several months.

Are zinnias easy to grow?

Yes, zinnias are generally easy to grow and care for. They are tolerant of a wide range of soil types and can be grown in a variety of conditions, including full sun to partial shade.

Does zinnia come back every year?

Zinnias are annual plants, which means they complete their life cycle in one growing season and do not come back the following year. However, they produce seeds that can be collected and planted the next growing season.

Do zinnias only bloom once?

Zinnias are annual plants, meaning they complete their life cycle in one growing season. They will bloom continuously throughout the growing season, which can last several months, as long as the spent flowers are deadheaded regularly. However, once the plant reaches the end of its life cycle, it will die and need to be replanted the following year.