How to Grow Cannabis
Cannabis sativa
Cannabis is a fast-growing warm-season annual that thrives in full sun with fertile, well-drained soil. Start seeds indoors 3 weeks before last frost, then transplant out once nights stay above 10°C. Photoperiod varieties flower naturally as days shorten below 12-14 hours in late summer; autoflower varieties flower on their own schedule regardless of light. Feed heavily with nitrogen during vegetative growth, then switch to phosphorus and potassium once flowering begins. Good airflow is essential — bud rot and powdery mildew thrive in humid, stagnant conditions. Harvest when trichomes turn milky to amber; dry and cure slowly for best quality.
When to Start
Start seeds indoors 3 weeks before your last frost date. Transplant outdoors once night temperatures stay above 10°C and soil has warmed to at least 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.
Growing Conditions
- Min. soil temperature
- 15°C+
- Germination temperature
- 20–25°C
Enter your last frost date to see your dates
- 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.
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 Tender.
