Marijuana is a flowering plant in the Cannabis genus that produces high concentrations of THC, the compound responsible for its psychoactive effects. It grows as an annual herb, completing its entire life cycle in one season, and has been cultivated for thousands of years for both recreational and medicinal use. What makes marijuana distinct from its close relative hemp is a single legal threshold: cannabis containing more than 0.3 percent THC by dry weight is classified as marijuana, while anything at or below that level is hemp.
How the Plant Is Structured
A marijuana plant has a central stalk with branches extending outward, covered in large, iconic fan leaves. Those broad, fingered leaves are the plant’s solar panels. They capture sunlight, store water, and drive photosynthesis, but they contain very few of the compounds people actually use the plant for.
The real chemical activity happens in the flowers, commonly called buds. At the base of each flower cluster sit small, teardrop-shaped structures called bracts. These carry the highest density of resin glands on the entire plant and account for most of the weight, THC, and other active compounds in harvested buds.
Covering the buds and surrounding sugar leaves are trichomes: tiny, mushroom-shaped glands that look like a frosty, crystalline coating. Trichomes are the plant’s chemical factories. They produce all of marijuana’s cannabinoids, terpenes, and flavonoids. Though trichomes appear mostly on flowers, smaller numbers also grow on stems, branches, and leaves.
Male and Female Plants
Marijuana plants come in male and female forms, and the difference matters enormously. Female plants produce the flower buds that people consume. Male plants produce pollen sacs, which look like small clusters of balls or grapes forming at the joints where branches meet the stem. Females are identifiable by their pistils, thin white hairs that emerge from the same locations.
If a male plant pollinates a female, the female shifts its energy toward producing seeds instead of resin-rich buds. That’s why growers remove male plants as soon as they’re identified. Unless someone is deliberately breeding new seed stock, males serve no purpose in a harvest-focused grow.
The Growth Cycle
From seed to harvest, a marijuana plant typically takes 15 to 25 weeks, depending on the variety and growing conditions. The life cycle breaks down into distinct stages:
- Germination (3 to 10 days): The seed cracks open and a taproot emerges.
- Seedling (2 to 3 weeks): The first sets of small, rounded leaves appear, and the plant establishes its root system.
- Vegetative growth (2 to 8 weeks): The plant puts on size rapidly, developing a thick central stem and branching outward. This is when it builds the structural framework that will eventually support heavy flower clusters.
- Flowering (6 to 8 weeks): Buds form, swell, and accumulate trichomes. The plant redirects nearly all its energy into flower production.
What triggers the shift from vegetative growth to flowering depends on the type of plant. Most traditional marijuana varieties are photoperiod plants, meaning they rely on day length to know when to flower. When nights grow longer (or when indoor growers switch their lights to a 12-hours-on, 12-hours-off schedule), the plant interprets this as late summer turning to fall and begins producing buds. Even a small light leak during the dark period can disrupt this process and prevent normal bud development.
Autoflowering varieties work differently. These plants carry genetics from a subspecies called Cannabis ruderalis, which evolved in northern climates with extreme light cycles. Autoflowers begin flowering roughly a month after germination regardless of how much light they receive. They can grow under 18 or more hours of light per day while still producing buds, which simplifies indoor growing considerably. The tradeoff is that autoflowers tend to stay smaller and yield less per plant than photoperiod varieties.
What the Plant Produces Chemically
Marijuana’s effects come from two main classes of compounds: cannabinoids and terpenes. THC is the most well-known cannabinoid and the one responsible for the “high,” but the plant produces dozens of others, including CBD, which does not cause intoxication. Researchers have identified over 100 distinct cannabinoids in cannabis, though any single plant will contain a smaller subset.
Terpenes are aromatic oils that give marijuana its wide range of scents and flavors. They also appear to influence how the plant’s effects feel. The most common terpenes each carry a distinct profile:
- Myrcene has an earthy, clove-like smell and is associated with deep body relaxation. It may also help other compounds absorb more efficiently through the skin.
- Limonene gives off a bright citrus scent. It’s linked to mood elevation and reduced anxiety.
- Pinene smells like a pine forest and acts as a natural anti-inflammatory. It also opens airways in the lungs.
- Humulene carries a woodsy, hoppy aroma (it’s also found in hops). It has anti-inflammatory properties and may act as a mild appetite suppressant.
- Eucalyptol produces a cooling, menthol-like scent and has antibacterial and antifungal qualities.
The specific ratio of cannabinoids and terpenes varies by strain, growing conditions, and harvest timing. This is why two different marijuana varieties can smell, taste, and feel dramatically different even though they come from the same species.
Hemp vs. Marijuana
Hemp and marijuana are the same plant species. The distinction is purely legal and chemical. Under U.S. federal law, cannabis with a total THC content of 0.3 percent or less by dry weight is classified as hemp. Anything above that line is marijuana. Hemp is legal nationwide following the 2018 Farm Bill, while marijuana remains federally restricted, though many states have their own legalization frameworks.
Visually, hemp and marijuana plants can look nearly identical. Some hemp varieties are bred for industrial fiber (tall, sparse plants with thin stalks), but CBD-rich hemp flower is often indistinguishable from marijuana to the naked eye. Studies from the National Institute of Justice have found that mislabeling between hemp and marijuana is a real problem in the commercial market, since the only reliable way to tell them apart is laboratory testing for THC content.
How Marijuana Is Typically Grown
Marijuana grows both outdoors and indoors, but the two approaches produce different results. Outdoor plants grow under natural sunlight and follow the seasonal light cycle, flowering as days shorten in late summer and reaching harvest in early to mid-fall in the Northern Hemisphere. These plants can grow quite large, sometimes exceeding six feet, with yields to match.
Indoor growing gives cultivators precise control over light, temperature, humidity, and nutrients. By manipulating the light schedule, growers can keep plants in the vegetative stage as long as they want, then trigger flowering on their own timeline. This allows for multiple harvests per year. Indoor-grown marijuana tends to have higher and more consistent cannabinoid and terpene concentrations because the environment is tightly controlled, though it requires significant electricity for lighting and climate management.
A third option, greenhouse cultivation, blends both approaches. Plants benefit from natural sunlight while growers maintain some environmental control. Light deprivation techniques (covering the greenhouse to simulate shorter days) let growers trigger flowering earlier than the natural season would allow.