Zinnia
Zinnia elegans
Zinnias are the ultimate summer cutting flower, producing a dazzling display of large, vibrant blooms in an incredible range of colours — from hot pinks and scarlets to soft pastels, lime greens, and even near-purple. They flower prolifically from July to the first frost, and the more you cut, the more they produce. They're half-hardy annuals, so sow under cover in April (they germinate quickly at 20°C) or direct sow after the last frost in late May. They hate root disturbance, so sow in individual modules or pots rather than seed trays. Plant out into the sunniest, most sheltered spot in your garden in rich, well-drained soil. Space 25–30cm apart. Zinnias thrive in hot summers and struggle in cool, wet ones — good drainage is essential to prevent mildew and stem rot. Deadhead regularly or, better still, cut for the house — cutting above a leaf node encourages branching and more flowers. 'Benary's Giant' series produces enormous, dahlia-like blooms on long stems perfect for cutting. 'Queen Lime Orange' and 'Zinderella Lilac' are modern favourites with sophisticated colours. 'Profusion' series are compact, mildew-resistant, and ideal for containers and borders.
Plan where to grow Zinnia using our vegetable garden planner.
When to Sow Zinnia
Sow zinnia in April, May. It flowers from July to October.
Time to Flower Zinnia
Expect flowers approximately 3 months after sowing.
Companion Plants for Zinnia
- French Marigold
Both are heat-loving annuals for a sunny spot, and marigolds' scent and hoverfly-attracting flowers are thought to help with aphids.
- Cosmos
Classic cut-flower partners that like the same warm, sunny conditions and flower together from midsummer to the frosts.
- Dahlia
Both are tender, sun-loving cut flowers planted out after the last frost, and they peak together in late summer.
Expected Yield
Each plant produces 15–25+ stems for cutting over the season. Vase life 7–10 days.
Growing Tips
Outstanding cut flower; the more you cut, the more they bloom
Pruning Zinnia
Pinch out the tips of young plants for more stems, then cut flowers often or deadhead; the more you pick, the more they flower.
Common Problems with Zinnia
Powdery mildew
White, powdery patches on leaves are common, especially in cool, damp weather or when plants are crowded. Space plants well for air circulation, water at the base in the morning (not overhead), and remove affected lower leaves. 'Profusion' series has excellent mildew resistance. Full sun and good drainage are the best preventatives.
Root rot and damping off
Seedlings and young plants are susceptible to damping off in cold, wet conditions. Use fresh compost for sowing, water from below, and ensure good ventilation. Don't sow too early — wait until compost temperature reaches 20°C. Avoid overwatering established plants; they prefer drier conditions.
Poor performance in cool, wet summers
Zinnias are heat-lovers and sulk in cool, rainy UK summers. Grow in the hottest, most sheltered spot available. In a poor summer, they perform much better in a greenhouse or polytunnel. Choose compact, mildew-resistant varieties like 'Profusion' for more reliable outdoor performance.
Zinnia: common questions
When should I sow zinnia in the UK?
Sow zinnia from April to May. Sow under cover (a greenhouse, windowsill or heated propagator) and plant out once the weather has warmed.
How far apart should I plant zinnia?
Space zinnia about 25cm apart. It grows to around 75cm tall. Sow seeds 1cm deep.
How long does zinnia take to germinate?
Zinnia seeds usually germinate in 5–7 days at 20°C, depending on temperature.
When does zinnia flower?
Zinnia usually flowers from July to October in the UK.
Does zinnia come back every year?
No. Zinnia is an annual: it grows, flowers and dies in one year, so sow it again each year. Some annuals self-seed if a few flowers are left to set seed.
When should I prune zinnia?
Pinch out the tips of young plants for more stems, then cut flowers often or deadhead; the more you pick, the more they flower.
What grows well with zinnia?
Good companions for zinnia include French Marigold, Cosmos and Dahlia. See the companion plants section above for why each one helps.
Is zinnia frost hardy?
No. Zinnia is tender and is damaged by frost, so keep it under cover until all risk of frost has passed and bring it in, or grow it under glass, when nights turn cold.
Plan your zinnia in the allotment planner
Drag and drop plants onto your plot and get personalised sowing reminders.
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