You can grow cannabis indoors with four things: a light, a space that holds it, moving air, and a way to keep temperature and humidity in range. Everything else is tuning. The core mechanic is photoperiod. Give a plant 18 hours of light a day and it stays in vegetative growth. Drop to 12 hours and it starts flowering. That single switch drives your whole calendar.
How Long Does It Take to Grow Cannabis? Seed to Harvest Timeline
The gear that earns its place
You do not need much, but you do need the right things. A 2x2 foot tent is a fine first size, and it is easier to control than a whole room.
how long does it take to grow cannabis
- Grow tent or a closet you can seal off from household light
- LED fixture sized to the footprint, roughly 30 to 40 watts of draw per square foot
- Inline exhaust fan with a carbon filter, vented outside the room
- One small oscillating fan inside the tent, not pointed straight at the canopy
- 24-hour mechanical timer
- Fabric pots, plus a medium such as coco coir or a peat-based mix
- pH meter, thermometer, and hygrometer
Light is the variable you cannot fake
Weak light produces tall, thin plants with loose buds, which is the most common first-grow disappointment. Hang the fixture so the canopy sits 12 to 18 inches below most modern LEDs, then raise it as the plant stretches. Leaf tips curling up and bleached patches mean you are too close. Slow, spindly growth means you are too far or too dim.
Keep a strict 18/6 schedule in veg and 12/12 in flower. A single light leak during the dark period can stall flowering or push a plant back into leaf growth.
Air, heat, and humidity
Plants breathe, and in a sealed tent that air goes stale. Run the exhaust continuously and let the passive intake pull fresh air in. Aim for roughly 70 to 80 F and 60 to 70 percent humidity during veg, then 68 to 78 F and 40 to 50 percent during flower. High humidity late in flower is how bud rot starts.
Medium and feeding
Soil or a peat mix is the forgiving choice: it buffers mistakes. Coco coir drains fast and rewards a steady, measured feed. Whatever you pick, keep the pH in range, about 6.0 to 6.5 for soil and 5.8 to 6.2 for coco, and feed at half the label strength the first few times. Overfeeding looks like burnt leaf tips. Underfeeding looks like pale lower leaves. The first is easier to fix than the second, so start light.
Week by week
- Weeks 1 to 2: seedling. Low light, high humidity, minimal water.
- Weeks 3 to 8: veg. Bright light, steady feed, top or bend the plant to shape it.
- Flip to 12/12 whenever you want, but expect the plant to roughly double in height.
- Weeks 1 to 8 of flower: buds form, swell, and ripen.
- Harvest when trichomes look milky with a few amber, then dry 7 to 14 days at about 60 F and 60 percent humidity.
- Cure in jars for 2 to 4 weeks, burping daily at first.
Mistakes I see most
- Watering on a schedule instead of by weight. Lift the pot. Light means dry.
- Adding more nutrients to fix a problem that is actually a pH problem.
- Skipping the exhaust fan to save money, then fighting heat and odor all grow.
- Harvesting by the calendar instead of by trichome color.
If you are growing for CBD
CBD-dominant and hemp cultivars grow the same way as high-THC ones. The difference is in the chemistry, not the horticulture. Cannabinoid levels shift through flowering and peak at different points depending on the cultivar, so check the trichomes rather than trusting the seed pack's day count.
Check your rules first
Indoor growing rules vary by state and by country, and they change. Hemp and cannabis are treated differently under federal law in the US, and some states allow home cultivation while others do not. Confirm what applies where you live before you buy a light.