How to Grow Lisianthus
Eustoma grandiflorum
When to Start
Sow indoors 13 weeks before last frost, or direct sow outdoors after frost risk has passed and soil reaches 15°C.
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Growth Stages
Approximate days from start
Care Essentials
- Balanced liquid feed fortnightly once transplanted. Switch to high-potash feed when buds form.
- Lisianthus are notoriously slow to start — seeds are tiny and need light, warmth, and patience. Sow early (January to February) for summer flowers. Once established they are rewarding cut flowers with exceptional vase life.
Companion Planting
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Growing Conditions
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- Sow indoors
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- Transplant out
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- First harvest
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Spacing & Planting
| Plant spacing | 20 cm |
| Row spacing | 30 cm |
| Sow depth | 0 cm |
| Mature height | 60 cm |
| Mature spread | 25 cm |
Space plants 15-20cm apart in rows 30cm apart. Lisianthus are slow-growing and compact, so close spacing helps stems stay upright and reduces the need for netting.
Care Guide
- Feeding
- Balanced liquid feed fortnightly once transplanted. Switch to high-potash feed when buds form.
- Watch for
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- Aphids
- Fungus gnats
- Botrytis
- Fusarium wilt
Pests & Diseases
Pest Aphids
Identification: Clusters of small green insects on shoot tips and flower buds, causing distorted growth and sticky honeydew.
- Squash by hand or blast off with a gentle water spray
- Spray with fatty acid-based insecticide
- Introduce biological controls such as Aphidius wasps under cover
- Spray with a contact insecticide containing deltamethrin
Pest Fungus Gnats
Identification: Tiny dark flies hovering around compost surface. Larvae are translucent white grubs in the top layer of compost that damage fine roots.
- Allow compost surface to dry between waterings
- Apply Steinernema feltiae nematodes as a biological drench
- Use yellow sticky traps to catch adults
- No effective chemical controls for home growers
Disease Grey Mould (Botrytis) Botrytis cinerea
Symptoms: Fuzzy grey mould on petals, stems, and leaves, especially in humid conditions. Buds may rot before opening.
Treatment: Remove and destroy affected parts promptly. Improve ventilation and reduce humidity.
Prevention: Space plants well for airflow. Avoid overhead watering. Remove spent flowers promptly.
Disease Fusarium Wilt Fusarium oxysporum
Symptoms: Yellowing and wilting of leaves on one side of the plant, progressing upwards. Stems may show brown discolouration when cut.
Treatment: Remove and destroy affected plants. Do not replant lisianthus in the same soil.
Prevention: Use fresh, sterile compost. Avoid overwatering. Rotate planting positions each year.
Disease Damping Off
Symptoms: Seedlings collapse at soil level, stems become thin and water-soaked. Patches of seedlings die suddenly.
Treatment: Remove affected seedlings and surrounding compost. Improve ventilation.
Prevention: Use clean pots and fresh compost. Water from below. Avoid overcrowding and overwatering. Maintain good air circulation.
Growing Conditions
| Min. soil temperature | 15°C |
| Germination temperature | 20–25°C |
| Base growth temperature | 10°C |
| Photoperiod sensitivity | day neutral |
Frequently Asked Questions
- How far apart should I plant Lisianthus?
- Plant Lisianthus 20cm apart with 30cm between rows.
- When does Lisianthus flower?
- Lisianthus typically flowers approximately 90 days after transplanting.
- Is Lisianthus frost hardy?
- Lisianthus is classified as Half Hardy.
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