Herb · Cannabaceae
Cannabis / Hemp
Cannabis sativa
Hand it full sun, warm soil, and steady nitrogen, and Cannabis sativa sprints from seed to harvest in one season.
Full sun
Every 2–7 days
59–86°F · 15–30°C
90–120 days
Overview
Cannabis sativa is a fast, hungry annual that shoots from seed to a tall stand of stems in a single season. It carries deep roots as a fiber and grain crop, and the very same species also grows for CBD and for its intoxicating flowers. Hemp and marijuana are not two plants but two ends of one species, sorted by how much THC the flowers hold.
How you grow it follows what you want from it. Fiber and grain crops go in thick and stay unpruned, rocketing up to 4 m (157 inches) in good ground. Plants raised for CBD or flower earn more room, a topping or two, and clean lower branches so light and air reach right into the buds.
Whatever the end use, the plant chases the same basics: full sun, warm well-drained soil, and plenty of nitrogen. It flowers as the days grow short in late summer, and that sets the harvest clock ticking. Settle one thing before you plant, though, since growing Cannabis sativa is restricted in many places: know the law.
Care
The short version: full sun, deep well-drained soil kept evenly moist without waterlogging, and a generous, nitrogen-forward feed right through the vegetative stretch, from spring planting to a late-summer harvest.
Light
Cannabis craves full sun, and the more direct hours it banks the better. It will manage in partial sun, but short light trims both the fiber yield and the strength of the flowers, so hand it an open, unshaded spot.
Water
Keep the soil evenly moist without ever letting it sit wet, since waterlogged ground breeds root disease. A field crop drinks roughly 25 to 30 inches of water over the season, with the heaviest pull coming during establishment and the vegetative surge.
Soil
Plant into deep, well-drained loam rich in organic matter, with the aeration that lets roots run freely. A pH between 6.0 and 7.5 suits it well, and good drainage counts every bit as much as fertility here.
Temperature
The plant powers along from 59°F to 86°F (15°C to 30°C). It needs real warmth to get rolling and holds no tolerance for frost, so wait for settled spring weather before it heads outside.
Humidity
Aim for the comfortable band of 40% to 70%. The sharper risk is humidity that climbs and hangs inside a thick canopy, because damp, still air is exactly what lets bud mold take hold.
Feeding
This crop is a heavy nitrogen feeder, often calling for 100 to 150 lb of nitrogen per acre depending on the end use. Feed it through the vegetative season with a nitrogen-forward balanced fertilizer, matching the rate to whether you are chasing fiber, grain, or flower.
Pruning
Fiber and grain crops stay untouched and never get pruned. For CBD and flower production, top the plants and strip the lower branches so air sweeps through and light drives deeper into the canopy.
Repotting
As an annual field crop it skips repotting. CBD starts earn one transplant out of the plug tray after hardening off, and from there they stay in the ground for the season.
Size & spacing
Plants stretch from 1 to 4 m (39 to 157 inches) tall depending on the type and how thickly they are sown, with a spread of 30 to 90 cm (12 to 35 inches). Fiber crops crowd in dense, while flower plants want plenty of elbow room for airflow.
When to plant
Cannabis runs as a warm-season annual that takes no frost at all. Start CBD transplants indoors about a month before the last frost, move plants or seed out once the soil hits at least 50°F (10°C) in late spring, and gather the crop from late summer once shortening days have switched on flowering.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 4 to 6 weeks before last frost for CBD transplants
- Plant: After last frost when soil reaches at least 50°F, typically late spring
- Harvest: Flowering triggered by shortening daylength in mid to late summer; fiber harvested at early flower, grain at seed maturity, CBD at peak cannabinoid
Hardiness
USDA hardiness zones: 3–10
Temperature: down to -40°C
Troubleshooting
Trouble with this crop tends to surface in two spots: the lower leaves or deep inside the flowers. Spot the early signs and you can step in before a small problem races through a dense stand. Match what you see below, then act while action still pays off.
Dense buds rotting gray-brown from the inside out
Watch for Botrytis, the gray mold that moves into thick flowers when air turns humid and stops moving. It eats outward from the core of the bud, so once that fuzzy gray fuzz reaches the surface the harm is already done. Cut out and destroy every infected piece, open the canopy so air flows through it, and bring the crop in the moment it is ready.
Fix:
- Remove and destroy infected material
- Increase airflow and reduce canopy density
- Harvest promptly when mature
Seedlings pinching at the soil line and tipping over
Suspect damping-off when young plants collapse, the work of soilborne fungi such as Pythium, Fusarium, and Rhizoctonia that surge in cold, soggy ground. The stem goes water-soaked and dark right at the soil line, and the seedling drops over. Sow into warm, well-drained beds with clean, treated seed, and back off the watering so the surface never stays wet.
Fix:
- Improve drainage
- Avoid overwatering
- Plant into warm soil
Lower leaves turning pale and yellow while the plant is still climbing
Reach for the nitrogen when the bottom leaves drain to yellow, because this crop eats hard and runs short fast. The oldest foliage fades first, then the color loss marches upward as the plant pulls nitrogen toward fresh growth. Pin it down with a tissue or soil test, then side-dress or fertigate to match the rate to your crop and its stage.
Fix:
- Side-dress or fertigate with a nitrogen source
- Match N rate to end use and growth stage
Toxicity
Keep this one well clear of animals. The plant's main active compound is THC, which is toxic to pets and brings on clear neurological signs in cats, dogs, and horses. For people, the THC is psychoactive and runs stronger in marijuana types than in low-THC hemp, and growing the plant is legally restricted in many places, so check the law where you live before you plant.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Severe
Cats take the THC badly. Look for deep lethargy, a wobbly, uncoordinated walk, vomiting, dilated pupils, a dropping body temperature, and dribbling urine, and at higher doses the picture can tip into seizures or coma.
Dogs Severe
A dog that gets into any part of the plant or a dried product turns dull and unsteady on its feet, often vomiting, leaking urine, and reacting to sound and touch. A slow heart rate and a low body temperature show up commonly, and severe cases bring on seizures or coma.
Horses Toxic
The same THC reaches horses too. A horse that grazes the plant grows sluggish and unsteady, often off its feed, with a slowed heart rate and clear depression.
Rabbits Toxic
No safe nibble exists here. The THC works on rabbits much as it does on other mammals, leaving them dull, off-balance, and sluggish, so keep every part of the plant out of reach.
Livestock Caution
Cattle, goats, and sheep tend to pass over the bitter plant, but an animal that does eat it can turn lethargic and unsteady from the THC. Fence stock well away from any planting to stay safe.
Birds Caution
Pet birds run small and sensitive, so even a scrap of plant material or a whiff of smoke can leave them dull and off balance. Treat it as strictly off-limits.
People Caution
The plant's THC is psychoactive and intoxicating, running stronger in marijuana types than in low-THC hemp. Cultivation is legally restricted in many places, so check the laws where you live, and keep all plant material and any product well away from children and pets.
Keep all plant material, dried product, and edibles away from pets; THC is the primary toxic principle.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Cultivars get bred for wildly different jobs, from fiber and grain to high-CBD flower. These three map out the range worth knowing.
Fedora 17
A monoecious French fiber and grain cultivar bred for low THC and stands that come up beautifully even.
Futura 75
A dioecious dual-purpose variety grown across Europe for fiber and grain alike.
Cherry Wine
A photoperiod CBD type chosen for its high cannabidiol while keeping THC within legal limits.
How to propagate
Cannabis takes off readily from seed for field crops, or from cuttings when a grower wants exact copies of a chosen plant.
SeedEasy
Direct sow after last frost into warm soil for fiber and grain crops · 7 to 14 days to emergence
Seed leads the way for fiber and grain crops. Direct sow after the last frost once the soil has warmed, and the seedlings push up in 7 to 14 days. Starting from seed brings genetic variability and the mixed male and female plants of a dioecious stand.
Stem cuttingsModerate
Take cuttings from vegetative mother plants before flowering · 2 to 3 weeks to root
Cuttings let CBD and floral growers clone their best plants exactly. Take them from vegetative mother plants before flowering starts, and they root in 2 to 3 weeks into uniform, high-cannabinoid females that match the parent.
Myths
Industrial hemp will get you high like marijuana.
Hemp carries a legal definition: Cannabis sativa with no more than 0.3 percent delta-9 THC. That amount is far too little to be intoxicating, which is precisely why the law sets its line right there.
Hemp and marijuana are two different plant species.
They share one identity, the same species, Cannabis sativa. What divides them is a legal cutoff drawn by THC concentration, not any botanical gap between two kinds of plant.