Herb · Cannabaceae
Cannabis / Hemp
Cannabis sativa
Given full sun, warm soil, and steady nitrogen, Cannabis sativa drives from seed to harvest within a single 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 builds a tall stand of stems in one season. It has a long record as a fiber and grain crop, and the very same species is also grown for CBD and for its intoxicating flowers. Hemp and marijuana are not separate plants but two ends of one species, sorted by how much THC the flowers carry.
The way you grow it follows from what you want out of it. Fiber and grain crops are sown thick and left unpruned, and in good ground they reach up toward 4 m (157 inches). Plants raised for CBD or flower get more space, a topping or two, and their lower branches cleared so light and air can move to the buds where it counts.
Whatever the end use, the basic requirements hold steady: full sun, warm well-drained soil, and ample nitrogen. The crop flowers as days shorten in late summer, and that response is what sets the harvest clock. Before you plant, settle the legal question, because growing Cannabis sativa is restricted in many places.
Care
The short version: full sun, deep well-drained soil kept evenly moist without waterlogging, and a generous, nitrogen-forward feed through the vegetative stretch, running from a spring planting to a late-summer harvest.
Light
Cannabis wants full sun, and the more direct hours it gets the better. It will tolerate partial sun, but reduced light lowers both fiber yield and flower strength because the plant has less energy to build them, so give it an open, unshaded spot.
Water
Keep the soil evenly moist and never let it sit wet, since waterlogged ground starves the roots of air and breeds root disease. A field crop draws roughly 25 to 30 inches of water over the season, with the heaviest demand falling during establishment and the vegetative push.
Soil
Plant into deep, well-drained loam rich in organic matter, with the aeration roots need to run deep. A pH between 6.0 and 7.5 keeps nutrients available to the crop, and here good drainage counts for as much as fertility.
Temperature
The plant performs best from 59°F to 86°F (15°C to 30°C). It depends on warmth to get moving and has no frost tolerance at all, so hold it back until spring weather has settled.
Humidity
Around 40% to 70% is the comfortable band. The real hazard is humidity that climbs and lingers inside a thick canopy, because damp, still air is exactly the condition bud mold needs to take hold.
Feeding
This is a heavy nitrogen feeder, frequently calling for 100 to 150 lb of nitrogen per acre depending on the end use. Feed through the vegetative season with a nitrogen-forward balanced fertilizer, and match the rate to whether the crop is bound for fiber, grain, or flower.
Pruning
Fiber and grain crops are left untouched and never pruned. For CBD and flower production, top the plants and strip the lower branches so air moves freely through the stand and light reaches deeper into the canopy where the buds form.
Repotting
As an annual field crop it is not repotted. CBD starts get one transplant out of the plug tray after hardening off, and from there they finish the season in the ground.
Size & spacing
Plants range from 1 to 4 m (39 to 157 inches) tall depending on type and sowing density, with a spread of 30 to 90 cm (12 to 35 inches). Fiber crops go in dense for tall, straight stems, while flower plants need far more room for the airflow that keeps mold off the buds.
When to plant
Cannabis is a warm-season annual with no tolerance for frost. Start CBD transplants indoors about a month before the last frost, move plants or seed outside once the soil reaches at least 50°F (10°C) in late spring, and harvest from late summer once shortening days have triggered 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 in this crop tends to surface either in the lower leaves or deep inside the flowers. Read the early signs and you can intervene before a small problem moves through a dense stand. Match what you see to the cases below, then act while action still changes the outcome.
Dense buds rotting gray-brown from within
This is Botrytis, the gray mold that establishes inside thick flowers when the air stays humid and still. The fungus advances outward from the core of the bud, so the fuzzy gray sporulation on the surface only appears after the interior is already lost. Cut out and destroy every infected piece, open the canopy to move air through it, and bring the crop in as soon as it is mature.
Fix:
- Remove and destroy infected material
- Increase airflow and reduce canopy density
- Harvest promptly when mature
Young seedlings collapsing at the soil line
This is damping-off, driven by soilborne fungi such as Pythium, Fusarium, and Rhizoctonia that take hold in cold, wet ground. The pathogens attack the tender stem at the soil line, where the tissue turns water-soaked and dark and can no longer hold the seedling upright, so it topples. Sow into warm, well-drained beds using clean, treated seed, and ease off the watering so the surface never stays saturated.
Fix:
- Improve drainage
- Avoid overwatering
- Plant into warm soil
Older leaves turning yellow from the bottom of the plant up
What you are seeing is nitrogen deficiency, and it appears readily because this is such a hungry feeder. Nitrogen is mobile inside the plant, so when supply runs short the crop strips it from the oldest leaves to fund new growth, which is why the pale color starts low and climbs. Confirm the cause with a tissue or soil test, then side-dress or fertigate at a rate matched to the crop and its growth stage.
Fix:
- Side-dress or fertigate with a nitrogen source
- Match N rate to end use and growth stage
Toxicity
This is a plant to keep away from animals. Its principal active compound is THC, which is toxic to pets and produces 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 planting.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Severe
Cats respond strongly to the THC. The clinical picture includes deep lethargy, a wobbly, uncoordinated walk, vomiting, dilated pupils, a falling body temperature, and dribbling urine, and at higher doses it can progress to seizures or coma.
Dogs Severe
A dog that eats any part of the plant or a dried product becomes dull and unsteady on its feet, frequently vomiting, leaking urine, and overreacting to sound and touch. A slowed heart rate and a low body temperature commonly follow, and the worst cases bring on seizures or coma.
Horses Toxic
Horses are affected by the same THC. One that grazes the plant grows sluggish and unsteady, often refuses feed, and shows a slowed heart rate alongside clear depression.
Rabbits Toxic
There is no safe nibble for a rabbit. The THC acts on them as it does on other mammals, leaving them dull, off-balance, and sluggish, so keep every part of the plant out of their reach.
Livestock Caution
Cattle, goats, and sheep tend to refuse the bitter plant on their own, yet an animal that does eat it can turn lethargic and unsteady from the THC. Fence stock well away from any planting as a precaution.
Birds Caution
Pet birds are small and sensitive, so even a trace of plant material or smoke can leave them dull and off balance. Keep it entirely off-limits to them.
People Caution
The THC in the plant is psychoactive and intoxicating, and it runs stronger in marijuana types than in low-THC hemp. Cultivation is legally restricted in many places, so confirm the laws where you live, and store 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 are bred for distinctly different jobs, from fiber and grain through to high-CBD flower. These three mark out the range worth knowing.
Fedora 17
A monoecious French fiber and grain cultivar bred for low THC and the even stands a uniform crop depends on.
Futura 75
A dioecious dual-purpose variety planted widely across Europe where growers want both fiber and grain from one crop.
Cherry Wine
A photoperiod CBD type selected for high cannabidiol while keeping its THC inside legal limits.
How to propagate
Cannabis comes readily from seed for field crops, and from cuttings when a grower needs exact copies of one chosen plant.
SeedEasy
Direct sow after last frost into warm soil for fiber and grain crops · 7 to 14 days to emergence
Seed is the standard route for fiber and grain. Direct sow after the last frost once the soil has warmed, and emergence follows in 7 to 14 days. Because seed carries genetic variability, the result is the mixed stand of male and female plants that a dioecious crop naturally produces.
Stem cuttingsModerate
Take cuttings from vegetative mother plants before flowering · 2 to 3 weeks to root
Cuttings let CBD and floral growers reproduce a chosen plant exactly. Take them from vegetative mother plants before flowering starts, since flowering shifts the plant away from the growth needed to root well, and they root in 2 to 3 weeks into uniform, high-cannabinoid females that match the parent.
Myths
Smoking industrial hemp will get you high the way marijuana does.
By law, hemp is Cannabis sativa carrying no more than 0.3 percent delta-9 THC. That concentration is far too low to be intoxicating, which is precisely where the legal threshold is set.
Hemp and marijuana belong to two separate plant species.
Both are the same species, Cannabis sativa. The line between them is a legal one defined by THC concentration, not a botanical difference between two distinct plants.