How to Grow Cannabis
Cannabis sativa
When to Start
Sow indoors 3 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
- High-nitrogen feed during vegetative growth; switch to high-phosphorus/potassium feed once flowering begins. Reduce feeding in the final 2 weeks before harvest.
- Legal status varies by jurisdiction — check local laws before growing. Photoperiod varieties require 12/12 light cycle to trigger flowering; outdoors this happens naturally as days shorten in late summer. Autoflower varieties flower regardless of light cycle and are faster but typically smaller.
Companion Planting
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Growing Conditions
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- Sow indoors
- —
- Transplant out
- —
- First harvest
- —
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Spacing & Planting
| Plant spacing | 60 cm |
| Row spacing | 90 cm |
| Sow depth | 1 cm |
| Mature height | 150 cm |
| Mature spread | 60 cm |
Wide spacing improves airflow and reduces bud rot risk. Autoflower varieties can be grown closer (45 cm) due to smaller stature.
Care Guide
- Feeding
- High-nitrogen feed during vegetative growth; switch to high-phosphorus/potassium feed once flowering begins. Reduce feeding in the final 2 weeks before harvest.
- Watch for
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- Spider mites
- Aphids
- Fungus gnats
- Bud rot (Botrytis)
- Powdery mildew
Pests & Diseases
Pest Aphids
Identification: Clusters of small soft-bodied insects on new growth and undersides of leaves; sticky honeydew residue
- Insecticidal soap spray
- Strong water jet to dislodge
- Introduce ladybirds or lacewings
- Pyrethrin-based spray (check local regulations)
Pest Spider Mites
Identification: Tiny moving dots on leaf undersides; fine webbing between leaves; stippled, bronzed foliage
- Neem oil spray
- Predatory mites (Phytoseiulus persimilis)
- Increase humidity temporarily
- Miticide spray (check local regulations)
Pest Fungus Gnats
Identification: Small dark flies hovering around soil; larvae damage roots in wet compost
- Allow soil surface to dry between waterings
- Yellow sticky traps
- Beneficial nematodes (Steinernema feltiae)
- Bacillus thuringiensis israelensis (Bti) drench
Disease Powdery Mildew Golovinomyces cichoracearum
Symptoms: White powdery coating on upper leaf surfaces; leaves curl and yellow
Treatment: Remove affected leaves; apply potassium bicarbonate or dilute milk spray
Prevention: Good airflow, avoid overhead watering, keep humidity below 50% during flowering
Disease Bud Rot (Botrytis) Botrytis cinerea
Symptoms: Grey-brown mould inside dense buds; affected tissue turns slimy and collapses; spreads rapidly in humid conditions
Treatment: Remove and destroy affected buds immediately; do not compost. Improve airflow urgently.
Prevention: Keep humidity below 50% during flowering, ensure good airflow through canopy, avoid dense overcrowded buds through defoliation
Growing Conditions
| Min. soil temperature | 15°C |
| Germination temperature | 20–25°C |
| Base growth temperature | 10°C |
| Photoperiod sensitivity | short day |
Frequently Asked Questions
- How far apart should I plant Cannabis?
- Plant Cannabis 60cm apart with 90cm between rows.
- When can I harvest Cannabis?
- Cannabis is ready to harvest approximately 90 days after transplanting.
- Is Cannabis frost hardy?
- Cannabis is classified as Half Hardy.
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