How to Grow Basil
Ocimum basilicum
Tender basil craves warmth, full sun, and free-draining, fertile soil or compost. Start seed indoors in late winter–spring, then plant out only after nights are reliably frost-free. Keep growth steady with even moisture and light, regular feeding; cold, drought and waterlogging all trigger setbacks and bitterness. Pinch out the growing tip to promote bushiness and better leaf yields. Harvest little and often; avoid stripping a plant bare in one go. Let a few stems flower late in the season for pollinators and seed, but remove most buds to keep leaves coming.
When to Start
Start seeds indoors 4 weeks before your last frost date. Transplant outdoors once night temperatures stay above 10°C and soil has warmed to at least 18°C.
Don't know your frost date? Find it here →
Growth Stages
Approximate days from start
Care Essentials
- Light liquid feed every 2 weeks. Don't overfeed — reduces flavour.
- Needs warmth — minimum 10°C. Water in the morning, not evening. Supermarket basil is multiple seedlings — repot and separate.
Companion Planting
Tomato, Pepper, Chilli
Growing Conditions
- Min. soil temperature
- 18°C+
- Germination temperature
- 20–25°C
Pet Safety
- Sow indoors
- —
- Transplant out
- —
- First harvest
- —
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Spacing & Planting
| Plant spacing | 20 cm |
| Row spacing | 25 cm |
| Sow depth | 0 cm |
| Mature height | 45 cm |
| Mature spread | 30 cm |
Allows for good air circulation to prevent fungal issues. Can be planted closer (20 cm) if harvested frequently.
Companion Planting
Grows well with
Basil's volatile linalool and eugenol compounds disrupt the olfactory navigation of tomato hornworms and whiteflies, reducing infestation without sprays. Plant within 30 cm of tomato stems for peak volatile concentration.
▼Basil's aromatic oils mask the scent cues that aphids use to locate pepper plants, lowering aphid colonisation rates. Interplant one basil for every two pepper plants for effective coverage.
▼Basil's monoterpenes — notably ocimene — deter aphids and spider mites that commonly afflict chilli plants in warm conditions. Keep plants touching or within 20 cm for the strongest repellent effect.
▼Basil's pungent volatile oils confuse the asparagus beetle's host-finding behaviour, reducing egg-laying on emerging spears in spring. Plant basil at the bed edges where beetles first land.
▼Keep away from
Both basil and sage release competing volatile compounds — sage's terpenes appear to inhibit basil's growth and can reduce its essential oil content, diminishing its pest-repellent potency. Keep at least 50 cm between them.
▼Pests & Diseases
Pest Slugs and Snails
Identification: Chewed leaves, slime trails, particularly problematic for seedlings
- Physical barriers
- Beer traps
- Copper strips
- Hand picking
- Slug pellets (follow label instructions)
Pest Aphids
Identification: Small insects clustering on new growth and undersides of leaves
- Insecticidal soap
- Strong water spray
- Encourage ladybirds
- Approved systemic insecticides
Disease Powdery Mildew Various species
Symptoms: White powdery coating on leaves, more common in humid conditions
Treatment: Improve air circulation, remove affected leaves
Prevention: Good ventilation, avoid overcrowding, water at soil level
Disease Grey Mould (Botrytis) Botrytis cinerea
Symptoms: Fuzzy grey mould on leaves and stems
Treatment: Improve air circulation, remove affected parts
Prevention: Good ventilation, avoid overwatering, remove dead material
Disease Damping Off
Symptoms: Seedling collapse at soil level, stems become thin and weak
Treatment: Remove affected seedlings, improve growing conditions
Prevention: Use sterile compost, avoid overwatering, ensure good ventilation
Growing Conditions
| Min. soil temperature | 18°C |
| Germination temperature | 20–25°C |
| Base growth temperature | 10°C |
| Min. daylength to start | 11h |
| Photoperiod sensitivity | day neutral |
Frequently Asked Questions
- How far apart should I plant Basil?
- Plant Basil 20cm apart with 25cm between rows.
- When can I harvest Basil?
- Basil is ready to harvest approximately 40 days after transplanting.
- What grows well with Basil?
- Basil grows well with tomato, pepper, chilli.
- Is Basil frost hardy?
- Basil is classified as Tender.
