How to Grow Nemesia
Nemesia strumosa
Nemesia is a half-hardy annual for full sun to light shade and free-draining compost. Wonderfully fragrant with bicoloured flowers. Prefers cool conditions (below 25°C) — thrives in UK spring and autumn but may pause in summer heat. Usually bought as young plants. Plant out after last frost. Feed fortnightly with balanced fertiliser. Trim back when flowering slows for a fresh flush. Not frost-hardy; discard at season end or try overwintering in a cold frame.
When to Start
Sow indoors 7 weeks before last frost, or direct sow outdoors after frost risk has passed and soil reaches 10°C.
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Growth Stages
Approximate days from start
Care Essentials
- Balanced liquid feed every two weeks. Light feeder — avoid overfeeding which promotes leggy growth at the expense of flowers.
- Wonderfully fragrant bedding plant with bicoloured flowers in a huge range of colours. Thrives in cool conditions — perfect for UK spring and autumn. May stop flowering in hot spells but recovers when temperatures drop. Excellent for containers, window boxes, and bed edges.
Growing Conditions
- Min. soil temperature
- 10°C+
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- Sow indoors
- —
- Transplant out
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- First harvest
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Spacing & Planting
| Plant spacing | 15 cm |
| Row spacing | 20 cm |
| Mature height | 25 cm |
| Mature spread | 20 cm |
For compact bedding varieties. Creates a dense, fragrant carpet of colour at this spacing.
Pests & Diseases
Pest Aphids
Identification: Clusters of small green insects on shoot tips, sticky honeydew, distorted growth
- Blast off with water
- Soft soap spray
- Encourage ladybirds
- Pyrethrum-based contact insecticide
Disease Grey Mould (Botrytis) Botrytis cinerea
Symptoms: Fluffy grey mould on stems and flowers, especially in cool damp conditions. Plants rot from the base.
Treatment: Remove affected growth. Improve air circulation. Reduce overhead watering.
Prevention: Space plants for airflow. Avoid wetting foliage. Remove dead flowers and leaves promptly.
Growing Conditions
| Min. soil temperature | 10°C |
| Base growth temperature | 7°C |
| Min. daylength to start | 10h |
| Photoperiod sensitivity | day neutral |
Frequently Asked Questions
- How far apart should I plant Nemesia?
- Plant Nemesia 15cm apart with 20cm between rows.
- When does Nemesia flower?
- Nemesia typically flowers approximately 40 days after transplanting.
- Is Nemesia frost hardy?
- Nemesia is classified as Half Hardy.
