You can grow cannabis in a closet, a tent, a spare room, or a backyard bed. The workflow is the same either way: germinate, vegetate under long days, flip to short days to trigger flower, then dry and cure what you cut. A first grow takes 3 to 5 months from seed to jar. The plant forgives temperature swings. It does not forgive bad water, wrong pH, or a light leak in the dark cycle.
How Long Does It Take to Grow Cannabis?
Start with the legal question
Where you live decides what you can grow. Many US states allow home cultivation of THC cannabis with plant count limits, and some allow it only for registered medical patients. Hemp, defined as cannabis testing at 0.3% THC or less on a dry weight basis, falls under federal farm bill rules, but state agriculture departments still license and test it. Check your state's rules before you buy a seed. If home growing is off the table where you are, hemp-derived CBD is the legal path to the same plant family.
how to grow cannabis from seed
Set up the space and control the air
Indoors, a 4x4 foot tent with a 6 inch exhaust fan and a carbon filter handles four plants in soil. Outdoors, you want six or more hours of direct sun and ground that drains.
- Temperature: 70 to 80 F with lights on, no lower than 60 F with lights off
- Humidity: 50 to 60% in veg, 40 to 50% in flower
- Air: moving across the canopy, but not hammering one leaf
Good airflow does more for you than any additive. It keeps mold away and strengthens stems.
How to Grow Cannabis Indoors: A Comprehensive Guide
Pick your starting material
Feminized photoperiod seeds give you the most control because you decide when flower starts. Autoflowers flip on their own after a few weeks, which suits small spaces and short summers, though yields run smaller. Clones save time and lock in a known chemotype, but they arrive with whatever pests or viruses the mother had. If your goal is CBD flower, buy hemp cultivars from a breeder who publishes third-party cannabinoid tests. Bag seed from THC flower is a gamble on both sex and potency.
Light and schedule
Vegetative stage runs 18 hours on and 6 off. Flowering runs 12 hours on and 12 off, and that dark period has to be truly dark. A stray LED from a power strip or a crack in a tent seam can stall flower or push a plant to produce male flowers. For indoor LED, 30 to 40 watts of actual draw per square foot is a workable target. Outdoors, the season handles the schedule for you and plants stretch hard in late summer.
Medium, water, and nutrients
Soil is the easiest place to learn. A peat or coco blend with 25 to 30% perlite drains well and buffers pH mistakes. Water when the top inch of medium feels dry, and water until you get a little runoff. Aim for pH 6.0 to 6.5 in soil or 5.5 to 6.0 in coco and hydro. Keep the feed weak at first and raise it as the plant asks for more. Dark green clawed leaves mean too much nitrogen. Brown crispy tips mean the same thing.
Train for an even canopy
Light only penetrates so far. Topping once or twice in veg splits the main stem into two or four tops. Low stress training bends those tops outward so every bud site sits at the same height. Defoliate a few leaves at a time in flower, never all at once. An even canopy beats a tall plant almost every time on weight.
Flower, then harvest
Weeks 1 through 3 of flower are stretch. Weeks 4 through 8 are when buds fill out and swell. Stop feeding nitrogen in late flower and watch the trichomes instead of the calendar. A cheap jeweler's loupe tells you more than any schedule: clear means early, cloudy means peak, amber means past peak. Cut at cloudy with a few amber for a balanced effect. Flush with plain pH-adjusted water for the last week or two.
Dry and cure
Hang whole branches in a dark room at about 60 F and 60% humidity for 7 to 10 days. Smaller stems should snap, not bend. Then trim, jar, and burp the jars twice a day for the first week, once a day for the second. Curing for three to four weeks smooths the harsh edge and brings out aroma. Skip it and you get hay.
Mistakes that cost a whole grow
- Overwatering in the first two weeks, which drowns young roots
- Ignoring pH, then guessing at a deficiency that is really a lockout
- Letting the tent get above 85 F in flower
- Harvesting early because the buds look big enough
- Jarring before the stems snap, which invites mold
Keep notes on what you fed and when. The second grow is where most people get good, and records are what make that possible.