How to Grow Cannabis: Seed to Harvest Guide

How to Grow Cannabis

Grow cannabis in four stages. Germinate the seed. Run the seedling under 18 hours of light. Keep the plant in vegetation. Then cut the light to 12 hours to start flowering.

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Photoperiod plants need 10 to 16 weeks indoors. Autoflower plants skip the light change and finish in 10 to 14 weeks.

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Check state law first. Several states allow home grow. Other states ban it. Plant limits range from 2 to 12 per household.

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What You Need

• Seeds or clones
• Container: 3 to 5 gallons
• LED light: 200 to 400 watts for a 2x2 or 4x4 tent
• Exhaust fan and carbon filter
• Soil, coco, or a hydro system
• Nutrients with nitrogen, phosphorus, and potassium
• pH meter, thermometer, hygrometer

Step 1: Germinate

Place seeds between wet paper towels. Keep the towel in a dark spot at 70 to 85F. A taproot shows in 24 to 72 hours. Plant the seed 0.5 inch deep with the taproot pointing down.

Step 2: Seedling (Weeks 1 to 3)

Run 18 to 24 hours of light. Keep the room at 65 to 80F. Hold humidity at 60 to 70%. Light intensity: 100 to 300 PPFD. Water in a small ring around the stem.

Step 3: Vegetative (Weeks 3 to 8)

Set the timer to 18 hours on, 6 off. Raise PPFD to 400 to 600. Keep pH at 6.0 to 7.0 in soil, 5.5 to 6.5 in coco or hydro. Feed more nitrogen. Top or train the plant at node 4 or 5 to widen the canopy.

Step 4: Flowering (Weeks 8 to 18)

Switch photoperiod plants to 12 on, 12 off. Keep the dark period free of light leaks. Flowering takes 8 to 11 weeks by strain. Raise PPFD to 600 to 1000. Hold 65 to 80F. Drop humidity to 40 to 50%, then 30 to 40% in the last two weeks to limit bud rot.

Harvest

Check trichomes with a 60x loupe. Harvest when most are cloudy and 10 to 20% are amber. Clear trichomes mean low THC.

Dry and Cure

Dry whole branches at 60 to 70F and 45 to 55% humidity for 7 to 14 days. Stems snap when dry. Trim, then seal buds in glass jars. Open each jar for 10 minutes each day for the first week. Cure 2 to 4 weeks for flavor.

Common Problems

• pH drift locks out nutrients
• Overwatering causes droop and root rot
• Light burn bleaches top leaves
• Spider mites leave webbing under leaves
• Bud rot shows grey spots inside dense colas

Yield

A beginner grows 1 to 4 ounces per plant indoors. Yield climbs with light intensity, plant count, and time in vegetation.