Marijuana is grown: it is an organic material from the plant genus Cannabis. It is grown as a tall herb from seed (one of its street names is 'herb').
Most grass is raised outdoors, during the summer growing season. However, some is grown indoors under artificial light, with the 'hydroponic' method, which entails planting in vessels filled with gravel, which can drain easily into a collection trough. A nutrient solution is pumped into the vessels at certain intervals.
When the plant is harvested, it is hung upside down in a dark room for up to a week, and then the buds are trimmed from the stems. These buds contain the highest levels of THC (delta 9 Tetra-Hydro-Cannabinol), the psychoactive substance in hemp.
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"Marijuana' is an Hispanic term for the bud of the hemp plant. The species Cannabis sativa has generally higher THC levels than other species of hemp.