Annual bedding
How to grow petunias
Petunia × atkinsiana
Petunias are frost-tender bedding plants for full sun, at their best in baskets and pots. Sow in a heated propagator in February or March, or buy plug plants in April, and plant out in late May once frost has passed. After that, success comes down to three routine jobs: watering before the compost dries out, removing spent flowers with the seed pod behind them, and a top-dressing of dry fertiliser every five to six weeks from early July.
- Hardiness
- Half-hardy annual
- Position
- Full sun
- Soil
- Fertile, free-draining; pots and baskets
- Ideal pH
- 6.0 to 7.0
- Water
- Moderate to high in baskets; daily in hot weather
- Feeding
- Moderate feeder
Sowing and planting petunias
WhenSow Feb to Mar with heat or buy plugs; plant out late May; flowers Jun to Oct
Starting off
Sow Feb to Mar on the surface of moist compost at 21 to 24 °C without covering, as the dust-fine seed needs light; germination takes 7 to 14 days. Prick out at 2 cm tall and grow on at 15 °C; plant out after the last frost in late May. Plugs bought in Apr save the heat.
Spacing and planting
Bedding types 20 to 30 cm apart, trailing Surfinia types 30 to 45 cm; plant at the same depth as the plug. Fine in a 30 cm pot or basket, three plants per 35 cm basket.
Varieties worth growing
- Surfinia series
- The standard trailing petunia for baskets: vigorous, stems to 1 m, and it recovers from rain better than most. Raised from cuttings, so buy as plugs.
- Tumbelina series
- Double, ruffled and scented trailing flowers; best in a basket under the eaves, where rain cannot spoil the heavy blooms.
- 'Tidal Wave' series
- Seed-raised and very vigorous: it spreads as ground cover in a bed or will climb a support to a metre.
- 'Night Sky'
- Deep purple speckled with white; the pattern changes with temperature, with more white after cool nights.
- 'Frenzy' series (multiflora)
- Compact, upright bedding type with many smaller flowers that shrug off wet weather; the one to grow from seed for beds.
Petunias month by month
Timings are for central England. Allow two weeks later in the north and on cold, heavy soil.
- January
Nothing to do. Order seed or plug plants.
- February
Sow on the surface of moist compost in a heated propagator. Do not cover the seed.
- March
Last sowings. Prick out seedlings at 2 cm tall and grow on in good light.
- April
Buy plugs and pot them on. Keep frost-free and pinch out tips for bushy plants.
- May
Harden off for 10 days. Plant baskets and pots, and set them out in the last week once frost has passed.
- June
Deadhead, taking the seed pod with the flower. The base feed carries plants through this month.
- July
Top-dress baskets and pots early in the month and water in. Cut leggy stems back by half in the middle of the month. Water daily in heat.
- August
Second top-dress mid month. Keep watering and deadheading. Baskets may need water twice a day.
- September
A last top-dress late in the month if plants are still flowering well. Root a few cuttings of a favourite.
- October
Clear plants to the compost heap after the first frost.
- November
Nothing to do outdoors. Keep any cuttings just moist on a cool, bright windowsill.
- December
Nothing to do.
Feeding petunias
In the ground petunias need little. In baskets and pots they are hungry: frequent watering washes the compost clean within a few weeks, so a base feed with a little sulphate of potash at planting and a top-dressing of the same dry fertiliser every 5 to 6 weeks keep them flowering.
In pots and baskets they're hungry for potassium, a regular high-K feed sustains the long bloom.
Feeding plan
Planting, baskets and pots
5 g per litre of compost, the low end of the label, mixed in: about 40 g for a 35 cm basket holding 8 litres, or 60 g for a 30 cm pot holding 12 litres.
Planting, beds
About 100 g/m² raked into the top few centimetres before planting. On soil that grew a fed crop last year, none.
Planting, baskets, pots and beds
Baskets and pots: 1 g per litre of compost, the low end of the label, mixed in with the base feed: 8 g for a 35 cm basket holding 8 litres, or 12 g for a 30 cm pot holding 12 litres. Beds: 20 g/m² raked in with the base dressing. Once. It keeps the plants flowering and not just growing leaf.
Early July, mid August and, if still flowering well, late September: baskets and pots
4 g per litre of compost, the top of the label top-dress, because daily watering leaches a basket fast: about 32 g for a 35 cm basket holding 8 litres, or 48 g for a 30 cm pot holding 12 litres. Lift the stems, scatter it on the compost and water it in. Dressings are 5 to 6 weeks apart, the label interval.
Signs to watch
Young leaves yellow between the veins in a pot
Iron short, often from alkaline tap water
An acidic feed or chelated iron
Pale, thin growth and few flowers
Nutrients washed out of the basket
A light top-dress of the dry feed in the feeding plan, watered in
Lush leaves, few flowers
Too much nitrogen
Switch to a high-potash feed
Pests, diseases and problems
Sticky shoots and flower buds, green or pink insects on new growth
Aphids
Squash by hand or spray with a plant soap solution in the evening, wetting the undersides of the leaves; repeat after a week.
Young plants eaten to stumps soon after planting out
Slugs and snails
Grow plants on to a good size before planting, check under pot rims and basket edges at dusk, and water in the morning so the surface is dry by night.
Flowers turn to brown mush and grow grey fluff in wet spells
Grey mould on rain-damaged petals
Pick off spoiled flowers promptly, thin congested growth, and choose multiflora or Surfinia types for exposed positions.
Leaves mottled with pale streaks, flowers streaked or distorted, plants stunted
Virus, spread by aphids or on hands and knives
There is no cure: bin the plant, wash your hands, and do not take cuttings from it.
Plants wilt in wet compost, stems brown at the base
Root and stem rot from waterlogging
Check drainage holes are clear, never stand pots in saucers of water, and let the top centimetre dry between waterings in cool weather.
Pruning
Pruning and care
Deadhead by pinching off the whole spent flower including the seed pod behind it. Cut leggy stems back by half in mid-Jul and feed for a fresh flush. No staking; frost-tender, so compost after the first frost or overwinter a favourite as a cutting on a 10 °C windowsill.
Good to knowDeadhead trailing types; trim back leggy growth at midsummer.
Growing petunias in pots
This is a container plant first and a bedding plant second. Put three plants in a 35 cm basket or a 30 cm pot of peat-free multipurpose compost with the base feed mixed in. A basket in sun needs water every day from June and twice a day in a heatwave: water until it drips from the bottom, and if the compost has dried and shrunk from the sides, stand the whole basket in a bucket for half an hour. Hang doubles and large-flowered types under the eaves, out of the rain. Soft tap water or rainwater suits them better than hard water, which gradually turns the young leaves yellow.
Petunias: common questions
How often should I feed petunias in hanging baskets?
Top-dress basket petunias every 5 to 6 weeks from early July with a balanced dry fertiliser, watered in: 4 g per litre of compost, about 32 g for a 35 cm basket. Daily watering washes nutrients out of the small volume of compost, so the base feed from planting runs out within about six weeks. Pale leaves and fewer flowers in July mean the feeding has slipped.
Why are my petunias leggy with few flowers?
Petunias go leggy when they are not deadheaded, are short of light, or have run out of feed. Cut the long stems back by half in mid July, water well, and check the July top-dressing has gone on; new shoots flower again within two to three weeks. Remove each spent flower with the green seed pod behind it, not just the petals.
When can I put petunias outside in the UK?
Put petunias outside in late May in central England, once the risk of frost has passed, and a week or two later in the north. Harden them off for 10 days first by standing them out in the day and bringing them in at night. A single frost kills them.
Sources
Growing information on this page was checked against these references in November 2026. Feeding rates are Dr Forest label rates.
- How to grow petuniasBBC Gardeners' World