Zinnias Growing Guide

annual plants for wild gardens

With their vibrant colours and versatility, it’s no wonder zinnias are one of the most popular annual flowers for gardens. Ranging from petite, pom pom-shaped blooms to giant dahlia-flowered cultivars in every colour except blue, zinnias bring non-stop colour to beds, borders, containers and cut flower arrangements. Learning how to grow zinnias successfully is easier than you think. This comprehensive guide covers choosing the right zinnia varieties, tips for planting and care, and creative ideas for enjoying these cheerful blooms all season long.

As quintessential flowering annuals, zinnias are easy to grow, tolerate heat extremely well and supply armloads of cut flowers. With extra care taken when sowing seeds and attention given to regular watering and fertilization, zinnias will reward gardeners with a dramatic and diverse display of colour. Their versatility also means they can be used as edging plants, in containers on the patio or incorporated into beautiful cut flower bouquets. By following this guide on how to properly grow zinnias, anyone can cultivate a vibrant and prolific zinnia garden.

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Choosing the Right Zinnia Varieties for Your Garden

With so many zinnia varieties to select from, it’s important to choose types that match your colour preferences, growing conditions and ultimate use.

  • Dwarf zinnias like ‘Zahara Starlight Rose’ and ‘Zahara Fire’ grow 12 to 18 inches tall, work beautifully as edging plants in sunny beds and bloom prolifically in pots on the patio.
  • Giant dahlia or cactus flowered zinnias produce the large, shaggy bloomed flowers on tall plants. Try ‘Zowie Yellow Flame’ and ‘Benary’s Giant Wine’ for big, vibrant colour impact.
  • Cactus flowered zinnias feature large, flattened and quill-shaped petals that stand out nicely in arrangements. ‘Magellan Coral’ and ‘Purple Prince’ are two eye-catching varieties.
  • Cheerful pompon types like ‘Magellan Cherry’ and ‘Magellan Yellow’ work well in beds, pots or as long-lasting cut flowers.
  • Unique scabiosa-flowered zinnias display a mix of domed central discs and surrounding ray petals. Check out ‘Zinderella Purple’ and ‘Purple Baron’.
  • Mix packets contain an assortment of colours and flower forms ideal for casual gardens or cutting.

Planting Zinnias

One of the keys to successfully growing zinnias is understanding their preferences for planting time, site selection, spacing and depth when sowing seeds.

Zinnias thrive in consistently warm weather and should not be planted outdoors until after the average last spring frost date when soil and air temperatures have thoroughly warmed. Most gardeners sow zinnia seeds directly in the garden two to three weeks after the last expected frost once the soil has reached at least 60°F. The ideal window falls between late spring and early summer. Zinnias started too early often stall and struggle to establish.

Select a site with full sun exposure for at least six hours daily. Zinnias perform best in fertile, well-drained soil and even rich, amended beds. Before planting, loosen the top 6 inches of soil and mix in several inches of aged compost or other organic matter. This gives zinnia roots the light and nutrition needed to fuel vigorous growth.

When sowing zinnia seeds directly outdoors, plant them 1⁄4 to 1⁄2 inches deep and 6 to 12 inches apart depending on the expected mature size. This allows adequate airflow and room for plants to reach their mature width. Water the seeded area gently with a fine spray to avoid displacing seeds.

While starting with seeds is most common, many gardeners also opt for the convenience of transplanting store-bought zinnia seedlings. This method allows getting a jump start on the season. Take care when transplanting young starts by hardening or acclimating them outdoors for a few days before placing them in sunny garden beds. Water them thoroughly after transplanting to reduce any stress. Apply a balanced organic fertilizer or compost tea around transplants for the nutrients they need to keep growing vigorously.

Key points:

  • Choose site with full sun (6+ hours) and well-drained, fertile soil
  • Amend soil with aged compost/organic matter
  • Plant after last spring frost when soil has warmed
  • Water newly planted seeds gently to avoid displacing
  • Sow seeds 1⁄4-1⁄2 inch deep, 6-12 inches apart
  • Transplant store-bought seedlings after hardening off

On-going Zinnia Care

Caring properly for zinnias involves watering correctly, fertilizing occasionally, practicing good sanitation habits and watching for pests or diseases.

Newly planted zinnias require moist soil to sprout and become established. Water areas seeded with zinnia seeds daily with a fine spray. Once seedlings appear, switch to deeper, thorough watering twice a week. Established zinnia plants also prefer less frequent, deep soakings that encourage extensive root growth rather than frequent, light sprinkles. Allow the soil to partially dry down to around 1-inch depth before watering again. Container plantings may need more frequent irrigation depending on temperatures and exposure.

While zinnias thrive in average fertility levels, applying a balanced organic vegetable fertilizer once a month provides the nutrients plants need for lush growth and maximum flowers. Use one formulated for vegetables instead of high nitrogen plant foods that encourage excess foliage over blooms. Always follow label directions for correct product use and application rates.

Harvest, Arrange and Enjoy Zinnias

One of the greatest pleasures of putting in the effort to properly grow zinnias comes at harvest time. Collect zinnia flowers for arrangements by cutting each individually just above a set of healthy leaves with stem lengths ranging between 8 to 15 inches. For maximum vase life, strip off the lower leaves and place freshly cut zinnias directly into clean water. Re-cut 1⁄2 inch off stems every few days and replace the water to prolong their beauty indoors.

Zinnias make fast and simple additions to summer table centrepieces, window box arrangements or hand-tied bouquets. Mix colours, textures and shapes by combining them with filler flowers like baby’s breath and interesting foliage or herb sprigs. For dried arrangements, cut fully opened zinnia flowers and hang them upside down until completely dried before adding them to wreaths or displays.

In addition to beds, borders and containers, tuck zinnias among vegetables like tomatoes or peppers for a bright burst of colour. Plant them along a pathway, mailbox or fence for a welcoming pop of brightness visible from a distance. However they are used, heat and drought-resistant zinnias will reward gardeners with vivid, lasting colour from early summer until the first frost.

fAQs – How to Grow Zinnias

Many gardeners, from beginners to experts, have questions about successfully growing zinnias. Here are answers to some of the most common zinnia FAQs:

Q. What is the best time to plant zinnias?

The ideal time for planting zinnia seeds or transplants outdoors falls after all danger of spring frost has passed and soil temperatures have thoroughly warmed, generally late spring to early summer.

Q. How often should I water zinnias?

Newly seeded or transplanted zinnias require frequent moisture until roots establish. Water them daily. Mature zinnia plants prefer less frequent, long soakings of around 1-inch of water weekly, allowing the soil to partially dry down between waterings.

Q. How can I prevent pests and diseases from affecting my zinnias?

Practice good garden sanitation by cleaning up spent blooms, fallen leaves and debris regularly. Treat any affected plants promptly with appropriate organic pest control products. Take preventative measures by applying neem oil or insecticidal soap sprays early in the season.

Q. How long do zinnias bloom?

By deadheading spent zinnia flowers weekly and providing plants with adequate water and fertilization, zinnias will bloom prolifically from early summer often lasting until the first frost.

final thoughts

With their wide range of flower sizes and colours plus reliable performance, it’s easy to see why zinnias are one of the top picks for gardeners wanting vibrant, low maintenance beauty. By following the tips outlined here on how to properly grow zinnias from planting to care to harvest, anyone can create a spectacular zinnia display sure to catch eyes and uplift spirits!

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