Cannabis takes 3 to 6 months from seed to harvest. Indoor photoperiod plants finish in 10 to 16 weeks, autoflowering plants in 8 to 12 weeks, and outdoor plants run 16 to 24 weeks because they follow the seasonal light cycle. Add 2 to 4 weeks for drying and curing before the flower is ready to use.
Those ranges move with genetics, light, and pot size. A fast autoflower in a small container under a strong light can be cut at week 9. A long-flowering sativa grown outdoors may need 24 weeks or more.
How to Grow Cannabis from Seed
How long does each cannabis growth stage last?
- Germination: 1 to 7 days
- Seedling: 1 to 3 weeks
- Vegetative: 3 to 8 weeks (photoperiod plants)
- Flowering: 7 to 10 weeks
- Drying: 7 to 14 days
- Curing: 2 to 4 weeks
Add it up and you get 8 to 12 weeks for autoflowers, 10 to 16 weeks for indoor photoperiod plants, and 16 to 24 weeks for outdoor plants.
Germination: 1 to 7 days
A seed cracks and pushes out a taproot once it takes in water. Most seeds sprout in 24 to 72 hours in a warm, dark spot at 70 to 80 degrees Fahrenheit. A seed that sits for 10 days with no taproot is a dud, and more waiting will not fix it.
Seedling stage: 1 to 3 weeks
The sprout breaks the surface and opens its first round leaves, called cotyledons, then the first true serrated leaves. Roots are thin at this point, so light and water stay mild. Growth above the soil looks slow while the root system builds underneath.
Vegetative stage: 3 to 8 weeks
Here the plant adds leaves, branches, and height. Indoor photoperiod growers choose when to flip the lights to 12 hours on and 12 hours off, which starts flowering. A longer veg period means a bigger plant and a bigger harvest.
Autoflowers run this stage on their own clock. They begin flowering 3 to 4 weeks after sprouting no matter what light schedule you use, so the veg window stays short.
Flowering stage: 7 to 10 weeks
Buds form, swell, and ripen during the flowering weeks. Most photoperiod hybrids need 8 to 9 weeks of a 12/12 light schedule. Sativa-leaning strains can run 10 to 12 weeks, while many indicas finish near week 7 or 8.
Autoflowers flower for about the same stretch, 6 to 9 weeks, but the timer starts on its own.
Drying and curing: 3 to 6 weeks
Harvest is not the finish line. Hang plants to dry for 7 to 14 days at about 60 degrees Fahrenheit and 60% humidity until small stems snap instead of bend. Then cure the flowers in sealed jars for 2 to 4 weeks, opening the lids each day at first, to smooth out the smoke.
Is autoflower or photoperiod cannabis faster?
Autoflowers finish first. A healthy autoflower goes from seed to harvest in 8 to 12 weeks because it flowers on a genetic timer instead of waiting for short days. Photoperiod plants need 10 to 16 weeks indoors, and the grower decides how long veg lasts.
The trade-off comes down to control. Photoperiod plants handle topping and training with no risk to a fixed finish date, and you can clone a keeper mother plant. Autoflowers do not clone well and give you one harvest per seed.
Indoor vs outdoor grow times
- Indoor: 10 to 16 weeks for photoperiod plants, 8 to 12 weeks for autoflowers. You control the light, so you control the calendar.
- Outdoor: 16 to 24 weeks or more. Plants veg through long summer days, start flowering as daylight drops below about 12 hours, and finish in fall.
- Greenhouse: Somewhere between the two. Many growers use light-deprivation tarps to force flowering earlier than the season allows.
What changes the timeline?
- Genetics: Flowering time is strain-specific. Breeders list a range, and real plants often run a week or two past it.
- Light intensity: Weak light slows growth. A 12/12 flip is what triggers flowering indoors.
- Container size: Small pots root-bind plants and stall them before they reach full size.
- Temperature and humidity: Cold slows everything down. Heat stress stalls flower development.
- Nutrition: Too much nitrogen during flower delays ripening. Too little of any nutrient slows growth.
- Training: Topping and low-stress training add a week or two of veg but raise yield.
How do you know cannabis is ready to harvest?
Trichomes are the clearest signal. Check the resin glands on the buds with a jeweler's loupe or a phone microscope. Clear heads mean early, cloudy heads mean peak potency, and amber heads mean the cannabinoids are breaking down.
Pistils, the hairs on the flower, curl in and turn orange or brown as a second clue, but they are less reliable than trichomes. Breeder flower times and your own grow notes fill in the rest.
Check the buds, not the sugar leaves. Leaf trichomes ripen weeks ahead of the ones on the flower itself, so a leaf check can fool you into cutting early.
Does CBD hemp take the same time to grow?
Yes. Hemp grown for CBD follows the same stages as THC cannabis and runs a similar 10 to 16 weeks indoors. Field hemp goes in the ground in late spring and comes down in fall, often after 16 to 20 weeks.
One key difference: hemp must be harvested while THC stays at or under 0.3% on a dry weight basis under US federal law. That limit can force an earlier cut than the plant's peak CBD window, which is why lab testing drives the harvest date on hemp farms.
Frequently asked questions
Can you speed up a cannabis grow?
Yes, to a point. Autoflowers, an early 12/12 flip once the plant is big enough, steady temps, and strong light can shave weeks off a run. You cannot rush the flowering genetics themselves.
How long from seed to smoke?
Plan on 3 to 5 months in most cases, including 3 to 6 weeks of drying and curing. A fast autoflower with a short dry can get you there in about 10 weeks.
How long do clones take?
Clones skip germination and the seedling stage, so they save 1 to 3 weeks. A rooted clone vegged for 4 weeks and flowered for 9 weeks is ready to cut at about 13 weeks.
Do cannabis plants need 12 hours of light to flower?
Photoperiod plants do. They stay in veg under long days and switch to flower when the dark period reaches about 12 hours. Autoflowers flower on their own schedule regardless of light hours.