How to grow nemesia
Overview
Nemesia is a herbaceous annual or short-lived perennial grown for its colourful, fragrant flowers. It is a cool-season bedding plant that fills gaps in borders and containers, providing continuous bloom from late winter to spring. Growers must time planting carefully to avoid heat stress, as nemesia quickly declines in hot weather.
Varieties
- Nemesia 'Sunsatia' — Compact, heat-tolerant series with vibrant colours, ideal for Australian gardens.
- Nemesia 'Aromatica' — Strongly scented, bushy variety perfect for pots and borders.
- Nemesia 'Blueberry' — Blue and white bicolour flowers, excellent for cool-season colour.
Soil Preparation
Nemesia prefers slightly acidic to neutral soil (pH 6.0–7.0) with good drainage. Enrich with well-rotted compost or aged manure before planting. Avoid heavy clay soils that stay wet; if needed, raise beds or add sand and organic matter to improve drainage.
Growing Guide
Plant nemesia in a position with morning sun and afternoon shade, especially in warmer zones. Use well-drained soil enriched with organic matter, and space plants 20–30 cm apart. Pinch out tips when young to encourage bushiness. In subtropical areas, treat as a winter annual; in temperate zones, plant in autumn for spring flowers. Avoid planting in midsummer heat.
Sowing
Sow nemesia seeds on the surface of moist seed-raising mix, as they need light to germinate. Gently press seeds in but do not cover. Germination takes 7–14 days at 18–21°C. Transplant seedlings when they have 4–6 true leaves, spacing 20–30 cm apart. Direct sowing is possible in mild climates.
Care
Feed nemesia with a balanced liquid fertiliser every 2–3 weeks during active growth. After the first flush of flowers, cut plants back by one-third to encourage a second bloom and maintain compact shape. Deadhead regularly to prevent disease and prolong flowering.
Companion Planting
Nemesia pairs beautifully with pansies, violas, and alyssum for a colourful cool-season display. It also complements lobelia and dianthus. Avoid planting near heavy feeders like tomatoes, which may outcompete nemesia for nutrients.
Common Pests & Risks
Aphids are common on nemesia, especially in early spring; control with a strong water spray or insecticidal soap. Fungal diseases like powdery mildew and botrytis can occur in humid or crowded conditions; improve air circulation and avoid overhead watering. Remove affected leaves promptly.
Troubleshooting
Yellow leaves: overwatering or poor drainage — reduce water and improve soil. Brown leaf edges: heat stress or dry air — move to shadier spot and increase humidity. Leggy growth: too much shade or lack of pinching — move to brighter position and pinch tips. Powdery mildew: poor air circulation — space plants and avoid overhead watering. Few flowers: old plants or heat stress — cut back after first flush and feed.