How to grow sweet pea
Overview
Sweet pea is a fast-growing, climbing annual grown for its fragrant flowers and seasonal colour. It thrives in cool to mild conditions and needs full sun and regular picking to keep blooming. The seeds are toxic if eaten.
Varieties
- Cupani — An old-fashioned, highly fragrant bicolour sweet pea, ideal for cut flowers in Australian gardens.
- Matucana — A deep purple-blue variety with intense scent, popular for trellises and perfumed bouquets.
- Spencer — A classic large-flowered sweet pea with ruffled petals, excellent for show and cutting.
- Old Spice — A mix of highly scented, small-flowered sweet peas, perfect for cottage gardens and naturalising.
Soil Preparation
Sweet pea prefers rich, well-drained soil with a pH of 6.5–7.5. Before planting, dig in well-rotted compost or aged manure to improve fertility and moisture retention. Avoid heavy clay or waterlogged soil, which can cause root rot.
Growing Guide
Sow sweet pea seeds 2–3 cm deep in well-drained soil, 10–15 cm apart, in full sun. Provide a trellis, teepee, or netting for the vines to climb. Water regularly to keep the soil evenly moist, especially during early growth. Pinch out the growing tips when the plant is 15 cm tall to encourage bushier growth and more flowers. In hot weather, sweet pea slows down and may stop blooming, so plant early in the season for best results.
Sowing
Sow sweet pea seeds directly in the garden or in pots, 2–3 cm deep and 10–15 cm apart. Seeds germinate in 7–14 days in cool soil. Soak seeds overnight before planting to speed germination. Transplant seedlings carefully as they dislike root disturbance.
Care
Feed sweet pea with a balanced liquid fertiliser every two weeks during active growth. Train vines onto a trellis or teepee and pinch out tips to encourage bushiness. Remove spent flowers regularly to prolong blooming.
Companion Planting
Plant sweet pea near carrots, radishes, and lettuce, which benefit from the same cool conditions. Avoid planting near onions and garlic, which can inhibit sweet pea growth. Good companions also include nasturtiums and marigolds to repel pests.
Common Pests & Risks
Aphids are common on sweet pea; spray with a strong jet of water or use insecticidal soap. Mildew can appear in humid weather; improve air circulation and avoid overhead watering. Snails and slugs damage young seedlings; use barriers or bait early in the season.
Harvesting
Harvest sweet pea flowers when the first bloom opens fully, cutting long stems early in the morning. Pick regularly, every 2–3 days, to encourage more blooms and prevent the plant from setting seed. Remove faded flowers promptly to keep the plant productive.
Troubleshooting
Yellow leaves: overwatering or poor drainage; reduce water and improve soil. Brown leaf edges: heat stress or low humidity; provide afternoon shade in hot weather. Stunted growth: lack of support or poor nutrition; add trellis and feed with liquid fertiliser. Few flowers: too much nitrogen or not enough picking; reduce nitrogen and pick regularly. Mildew on leaves: poor air circulation; space plants wider and avoid overhead watering.