How to Grow Zinnia
Annual
Zinnias are colourful, heat-loving annuals with sturdy stems and flowers ranging from neat pompons to open daisy forms. They flourish in a warm, sunny summer and are especially useful for cutting. Although they can be grown throughout the UK, they need a sheltered site and patience in cool springs.
Planting
Sow zinnias under cover from April to May, one seed per module or small pot, at about 20 degrees C. Pot on only if roots fill the container, then harden plants off gradually. Plant out after all danger of frost, spacing 25 to 40 cm apart according to variety. Direct sow outdoors in late May or June only where soil is warm and the garden is sheltered. In Scotland and cooler northern sites, indoor sowing gives the best start.
Care
Grow in full sun with good air movement and water at the base in dry weather. Keep foliage as dry as practical when watering, as crowded, damp plants can develop mildew. Deadhead regularly or harvest blooms for the vase. Stake taller selections in windy positions. Feed container-grown plants lightly through summer if growth becomes pale or flowering slows.
Bloom time
Flowers generally appear from July to October, with an earlier start from indoor-raised plants in a warm southern garden. A cool, wet summer may delay flowering, particularly in exposed northern and Scottish sites.
Garden uses
Zinnias are ideal in sunny borders, cutting patches and generous pots. Their vivid colours pair well with cosmos, salvias and ornamental grasses. Choose open-centred, single varieties where pollinators are important; fuller double blooms are chiefly valued for their long-lasting, colourful display and cutting quality.
Tips
Wait for reliably mild weather before planting out: zinnias resent cold soil and frost. Give each plant enough room to dry after rain. Pick stems when flowers are fully open and firm, then remove any leaves that would sit below vase water. AGM varieties are a sound starting point.
Growing Zinnia: frequently asked questions
How do I grow zinnia in the UK?
Sow zinnias under cover from April to May, one seed per module or small pot, at about 20 degrees C.
When does zinnia flower?
Flowers generally appear from July to October, with an earlier start from indoor-raised plants in a warm southern garden.
How do I care for zinnia?
Grow in full sun with good air movement and water at the base in dry weather.
General guidance for UK gardens. Timing and hardiness vary by region and season; the RHS or a local garden centre can advise for your area. Page updated 18 Sep 2026.