How to Grow Petunia
Annual
Petunias are tender annual bedding plants prized for abundant trumpet-shaped flowers from early summer to autumn. They work best in warmth, sunshine and freely draining compost. Modern trailing and compact varieties offer a huge choice of colours, patterns and flower forms, making them staples for bright patios and front gardens.
Planting
Sow seed indoors from February to March on the surface of seed compost at around 21 degrees C, as seedlings need warmth and light. Most gardeners find plugs or young plants simpler. Pot or plant outside only after the last spring frost, usually from late May, spacing bedding types about 20 to 30 cm apart. Harden off carefully. In northern gardens and Scotland, keep plants sheltered until nights are reliably mild.
Care
Give petunias full sun and protect them from prolonged heavy rain where possible. Water pots thoroughly when the compost surface starts to dry, avoiding constant saturation. Remove faded flowers and seed pods from older varieties; many modern types need less deadheading but still benefit from trimming tired shoots. Feed container plants regularly with a suitable general fertiliser, following its label guidance.
Bloom time
Petunias flower from June to October, often beginning earlier in a warm, sheltered southern position. They perform best through warm, bright weather, while cold nights and persistent rain can reduce flowering in northern and western gardens.
Garden uses
Use compact petunias in tubs, bedding schemes and window boxes, and trailing varieties in hanging baskets or over retaining walls. Their saturated colours are effective in bold, repeated groups. Combine them with foliage plants for contrast and position pots close to paths or seating where the flowers can be enjoyed.
Tips
Do not plant out early simply because days are sunny: cold nights can check growth badly. Cut back leggy stems by about one third in midsummer, water well and allow plants to regrow. Good drainage is essential, particularly for baskets exposed to frequent summer rain.
Growing Petunia: frequently asked questions
How do I grow petunia in the UK?
Sow seed indoors from February to March on the surface of seed compost at around 21 degrees C, as seedlings need warmth and light.
When does petunia flower?
Petunias flower from June to October, often beginning earlier in a warm, sheltered southern position.
How do I care for petunia?
Give petunias full sun and protect them from prolonged heavy rain where possible.
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.