Zinnia seeds - Dahlia flowered mix has semi double flowers on strong growing stems. The beautifully formed bright flowers are excellent for cutting.

With their kaleidoscopic array of colours, few flowers can rival the radiant beauty of zinnias. These delightful blooms have long been cherished by gardeners around the world and are a firm favourite in cottage gardens and ornamental flower borders. Low maintenance and easy to grow, a patch of zinnias will provide an abundance of colourful flowers all summer long.

If you’ve never grown zinnias before, you’ll be pleasantly surprised at how simple it can be! We’ve got some great tips to help you grow zinnias from seed, guaranteeing a colourful floral display that will bring joy and delight into your garden.

What are zinnias?

Zinnias are annual flowering plants native to the warm regions of North and South America. Named after the German botanist Johann Gottfried Zinn, these enchanting flowers boast a rich heritage dating back centuries. Thanks to their vibrant hues and prolific blooms, zinnias have become a common sight in cottage gardens across the UK.

Zinnias are prized not only for their aesthetic appeal but also for their resilience and ease of cultivation. Thriving in full sunlight with well-drained soil, these hardy plants are remarkably tolerant of heat and drought, making them a reliable choice for gardeners in a range of different climates.

Best types of zinnias to grow

A member of the Asteraceae family, zinnias are available in an array of shapes, sizes, and colours, offering endless possibilities for keen gardeners. From delicate single-petaled varieties to extravagant double blooms, and from miniature dwarf cultivars to towering giants, there's a zinnia to suit every situation.

The most prevalent type of zinnia found in British gardens is zinnia elegans, also known as common zinnia. Famed for its classic beauty and vibrant colours, Zinnia elegans is the quintessential cottage garden plant, adding a graceful flash of colour and beauty to ornamental flower borders.

Popular common zinnia varieties in the UK include:

·       Giant Dahlia Flowered Mix

This variety produces large, double blooms in a mix of vibrant colours that closely resemble dahlias, ideal for adding bold splashes of colour to flower borders and cutting gardens.

·       Envy

Envy is a unique variety with lime-green flowers, adding a refreshing and unusual hue to garden beds and containers. It contrasts beautifully with other brightly coloured zinnias or serves as a focal point on its own.

·       Purple Prince

Purple Prince features stunning deep purple flowers with contrasting golden centres, adding a touch of richness and sophistication to garden displays and floral arrangements.

·       Candy Cane Mix

This mix includes zinnias with striped or bicolour petals in shades of pink, red, and white. 'Candy Cane Mix' creates a cheerful and playful effect in garden borders and attracts pollinators with its abundant blooms.

·       Peppermint Stick

Similar to peppermint candy, 'Peppermint Stick' zinnias boast striking bicolour flowers with red and white striped petals. This eye-catching variety adds vibrant charm to garden beds and container plantings.

How tall do zinnia grow?

Zinnias come in a variety of heights, depending on the specific cultivar. Generally, zinnias range in height from as low as 6 inches to as tall as 4 feet. These are the typical height categories for different types of zinnias:

·       Dwarf or Compact Varieties

These zinnias typically grow to a height of 6 to 12 inches, making them ideal for edging, containers, or small gardens where space is limited.

·       Intermediate Varieties

Intermediate zinnias grow to a height of around 18 to 24 inches, striking a balance between compactness and height. They are suitable for borders, mixed plantings, and cutting gardens.

·       Tall Varieties

Tall zinnias can reach heights of 2 to 4 feet or more, creating impressive backdrops and focal points in the garden. They are often used in mass plantings or as standalone specimens.

How to plant zinnia seeds

Propagating zinnias from seed is a straightforward process that allows you to grow these beautiful flowers from scratch. Zinnia plants love the warm summer days so are the seeds best sown outdoors after the danger of frost has passed and the soil has warmed up, typically in late spring or early summer. You can also sow zinnia seeds indoors 4 to 6 weeks before the last frost date and transplant seedlings outdoors once the weather is favourable.

When sowing zinnia seeds directly in the garden, select a sunny location with well-drained soil for planting zinnia seeds. Sow the seeds ¼ to ½ inch deep in rows or clusters about 12 to 18 inches apart. Flower Seeds started indoors should be sown at the same depth in individual pots or modules containing good-quality seed compost.

Keep the soil consistently moist but not waterlogged during the germination period, which usually takes 7 to 10 days. Water with a gentle spray to avoid disturbing the seeds.

Indoor-grown zinnia seedlings should be transplanted into their final growing position once they have developed several sets of true leaves and all risk of frost has passed.

How to care for zinnia plants

Caring for zinnia plants is relatively easy, and they will thrive and produce abundant blooms with just a little attention as and when necessary.

·       Watering

Keep the soil consistently moist but not waterlogged, especially during periods of dry weather. Water very well especially at dry spells at the baso of the plants.

·       Fertilising

Zinnias grown in good-quality soil that has plenty of well-rotted organic matter do not need any extra fertiliser. If your soil is poor and low in nutrients, use an organic fertiliser specifically formulated for flowering plants.

·       Deadheading

Remove spent flowers regularly by pinching them off at the base of the stem to encourage continuous blooming. Deadheading redirects the plant's energy from seed production to the development of new flowers.

·       Pruning

Pinch back the tips of zinnia stems when they reach 6 to 8 inches tall to promote a bushier growth habit. This encourages the development of more flowering stems and increases the overall flower production.

·       Mulching

Apply a layer of organic mulch, such as straw, shredded bark, or compost, around the base of zinnia plants to retain soil moisture, suppress weeds, and regulate soil temperature. Keep the mulch a few inches away from the stems to prevent the risk of fungal diseases and stem rot.   

·       Support

Provide support for tall or top-heavy zinnia varieties by staking individual plants or installing a trellis or plant support system. Use soft ties or garden twine to secure the stems to the support structure without causing damage.