Growing marijuana comes down to four things: a female plant, a light schedule that moves from long days to 12 hours of light and 12 of darkness to trigger flowering, a warm room that is not too humid, and patience until the resin glands mature. Everything else, from training to nutrients, is a way of getting more out of those basics. This guide covers the fundamentals that research supports, and it is honest about what varies from garden to garden.
Cannabis is an annual plant, so every grow runs the same cycle: germination, vegetative growth, flowering and harvest. A 2026 plant-science review describes the same four phases for the plant’s own life cycle, with seed formation in place of harvest (Betancourt et al., Plants, 2026). The rest of this page turns that cycle into a practical sequence.
Growing at Home: Washington and Oregon Law
Home growing is legal for adults 21 and older in Oregon, up to 4 plants per household, kept out of public view; see the statute (ORS 475C.305) and our Oregon marijuana laws guide. In Washington, home growing is legal only for registered medical patients. Under RCW 69.51A.210, a patient entered in the state medical cannabis authorization database may grow up to six plants by default, or up to fifteen if a health care professional recommends it. Adults who buy only at retail stores may not grow. See our Washington marijuana laws guide. Cannabis remains illegal under federal law, and local rules and landlord or HOA restrictions can add limits.
Basic Marijuana Growing at a Glance
| Stage | What changes | Conditions the research points to | Source |
|---|---|---|---|
| Seedling and clone | Roots and first leaves develop | Recommended relative humidity of 65 to 75% in the literature | Corredor-Perilla et al., 2025 |
| Vegetative growth | Stems and leaves build the plant’s structure | Relative humidity 50 to 70%; an indoor schedule of 16 hours of light and 8 of dark | Corredor-Perilla et al., 2025; Ijoma et al., 2025 |
| Flowering | Buds form and resin glands fill | 12 hours of light, 12 of dark; relative humidity 40 to 60% | Backer et al., 2019; Corredor-Perilla et al., 2025 |
| Harvest | Resin glands turn cloudy to amber | Roughly 60 to 70% amber trichomes is a common benchmark | Ijoma et al., 2025 |
Start With Genetics: Seeds, Clones and Plant Sex
Cannabis plants are usually either male or female. Researchers describe the plant as predominantly dioecious, with female plants carrying two X chromosomes and males an X and a Y, although hermaphrodite and monoecious plants do occur (Babaei and Torkamaneh, Plant Genome, 2026). That matters because only the female flower produces the resin-rich buds growers want. The National Cancer Institute notes that cannabinoid concentration is highest in the female flower (NCI PDQ, Cannabis and Cannabinoids).
Pollination also lowers quality. In the 2026 landrace study, researchers separated males from females before flowering began because pollination is known to reduce cannabinoid content (Babaei and Torkamaneh, 2026). For a home grower, the practical lesson is to remove any male plant as soon as it is identified, and to buy seed from a reputable seller who sells seed marketed as feminized, meaning bred to produce female plants.
A strain name is not a guarantee of identical plants. A 2019 meta-analysis noted that variety names do not always correspond to a plant’s genotype, which is why results from one garden do not always transfer to another (Backer et al., Frontiers in Plant Science, 2019).
Light: The Switch That Controls Everything
Cannabis is a short-day plant. Flowering is induced when day length falls below 12 hours, according to the meta-analysis above, and a 2025 review adds that the plant needs day lengths in roughly the 9 to 15 hour range to start flowering (Backer et al., 2019; Corredor-Perilla et al., 2025). That is why indoor growers keep plants on a long-day schedule while they build size, then cut the light to 12 hours to start flowers. One indoor protocol describes 16 hours of light and 8 of dark in vegetative growth, then a switch to 12/12 for flowering (Ijoma et al., J Cannabis Research, 2025).
A few cautions follow from the same research:
- Interrupting the night with light extends the perceived day length, which delays flowering in short-day plants (Grover et al., Plants, 2025). Keep the dark period dark.
- Continuous light is not better. In fiber-type plants, 24 hours of light damaged chloroplast membranes, while 16 hours of white light followed by 8 hours of dark improved photosynthetic efficiency (Corredor-Perilla et al., 2025).
- More light is not always more efficient. In the meta-analysis, higher light intensity raised THC per square meter but lowered yield per watt of lighting (Backer et al., 2019).
- LED fixtures give off little heat and can sit closer to the plants than older lamps, which lets light reach the lower canopy (Backer et al., 2019).
Temperature and Humidity
The 2025 review puts optimal growth at 25 to 35 degrees Celsius, or about 77 to 95 degrees Fahrenheit. Hotter is not better for flowers: in THC-rich and CBD-rich plants, raising day and night temperatures from 25/21 degrees to 31/27 degrees cut total cannabinoid yield sharply in one study, and the authors concluded that heat disrupted flower development (Corredor-Perilla et al., 2025).
Humidity matters just as much, and it is easy to overlook. The same team grew a plant at 37 to 58% relative humidity and another at 78 to 98%. The high-humidity plants flowered later, with flowering not seen until week 13, and had lower cannabinoid concentrations, which is why the paper’s title says elevated humidity decreases cannabinoid levels (Corredor-Perilla et al., 2025). High humidity also invites mold, so keep flowering rooms toward the dry end of the 40 to 60% range the literature recommends.
Shape the Plant: Training Basics
Left alone, cannabis tends to grow one dominant main stem and top bud, a trait called apical dominance. Growers interrupt it to build a flatter canopy with more bud sites. Gentle bending and tying is called low-stress training; cutting the growing tip is called topping (Ijoma et al., 2025). The 2025 review says growers commonly wait until a seedling has about five or six nodes before topping, and advises sterilizing scissors and washing hands, since every cut is an entry point for infection.
We cover the two main methods in detail in our guides to scrogging and trellising and to trimming cannabis plants.
When to Harvest
Timing is judged by the plant, not the calendar. The 2025 mainlining review says colas are typically ready when about 60 to 70% of the trichomes have turned amber, and notes that the exact timing depends on the cultivar, environment and technique (Ijoma et al., 2025). The 2026 landrace study used browning stigmas and a trichome shift from clear to amber or brown as its maturity signals (Babaei and Torkamaneh, 2026). A jeweler’s loupe or small magnifier is the usual tool for checking.
What This Guide Cannot Give You
Soil pH, feeding schedules and watering frequency vary with the growing medium, container size and cultivar, and we did not find reliable published numbers that apply to every home garden. Follow your seed company’s instructions and your nutrient maker’s chart, and adjust based on how the plant looks. For strain choices, see our list of the top strains to grow indoors and our strain directory. For the full plant cycle, read the cannabis plant life cycle.
Basic Marijuana Growing FAQ
How long does it take to grow marijuana?
It depends on the cultivar and the schedule, so there is no single number. Our strain guides list typical flowering times, such as 7 to 9 weeks for Northern Lights and 9 to 10 weeks for Blue Dream. Add the time spent in vegetative growth, which the grower controls.
How many hours of light does marijuana need?
Indoors, one protocol uses 16 hours of light and 8 of dark in vegetative growth, then 12 hours of each to flower. Flowering is triggered when days are shorter than about 12 hours.
What temperature is best for growing marijuana?
A 2025 review puts optimal growth at 25 to 35 degrees Celsius (77 to 95 degrees Fahrenheit), but flower quality can fall when temperatures climb toward the top of that range.
Can I grow marijuana at home in Washington or Oregon?
In Oregon, adults 21 and older can grow up to 4 plants per household, out of public view. In Washington, only registered medical patients may grow at home. Check our state guides before you start.
Why do growers remove male plants?
Males pollinate females, and pollination is known to reduce cannabinoid content. Only females produce the resinous flowers most people want.
Where do I buy marijuana legally while my plants grow?
Use our directory of licensed stores in Washington and Oregon.
For adults 21+ in legal states. General information, not medical advice.
