Herb · Cannabaceae
Cannabis / Hemp
Cannabis sativa
Given full sun, warm soil, and steady nitrogen, Cannabis sativa carries a garden 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 rises from seed to a tall stand of green within one season, lending real architecture to the back of a sunny plot. It carries a long history 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 a single species, sorted by how much THC the flowers hold.
The shape it takes in your garden depends on what you want from it. Fiber and grain crops are set in thick and left to themselves, climbing toward 4 m (157 inches) in good ground and reading as a dense green screen. Plants raised for CBD or flower are given room to breathe, a topping or two, and their lower branches cleared so light and air can settle around the buds.
Whatever its purpose, the plant asks for the same foundations: full sun, warm well-drained soil, and ample nitrogen. It comes into flower as the days draw short in late summer, and that turn of the light sets the rhythm of the harvest. The first thing to settle, well before a seed goes in, is the law, since growing Cannabis sativa is restricted in many places.
Care
The short version: full sun, deep well-drained soil kept evenly moist but never waterlogged, and a generous, nitrogen-forward feed through the vegetative stretch, carrying the plant from a spring planting to a late-summer harvest.
Light
Cannabis lives for full sun, and the more direct hours it draws the better it shows. It will manage in partial sun, yet shorter light thins both the fiber yield and the strength of the flowers, so give it an open, unshaded place in the garden.
Water
Keep the soil evenly moist and never let it sit wet, since waterlogged ground invites root disease. Across a season a field crop draws roughly 25 to 30 inches of water, leaning hardest on it through establishment and the vegetative push.
Soil
Set it in deep, well-drained loam rich in organic matter, with the aeration that lets roots reach down freely. A pH between 6.0 and 7.5 suits it well, and here good drainage counts every bit as much as fertility.
Temperature
The plant is at ease from 59°F to 86°F (15°C to 30°C). It wants warmth to find its feet and holds no tolerance for frost, so let settled spring weather arrive before it moves outdoors.
Humidity
A range of 40% to 70% keeps it comfortable. The real concern is humidity that rises and lingers within a thick canopy, since damp, motionless air is what opens the door to bud mold.
Feeding
This plant is a heavy nitrogen feeder, often calling for 100 to 150 lb of nitrogen per acre depending on what it is grown for. Feed through the vegetative season with a nitrogen-forward balanced fertilizer, tuning the rate to whether the goal is fiber, grain, or flower.
Pruning
Fiber and grain crops are left undisturbed, never pruned at all. For CBD and flower production, top the plants and clear the lower branches so air moves freely and light reaches deeper into the canopy.
Repotting
As an annual field crop it is never repotted. CBD starts take one transplant out of the plug tray after hardening off, and from there they settle into the ground for the season.
Size & spacing
Plants reach from 1 to 4 m (39 to 157 inches) tall, shaped by the type and by how thickly they go in, carrying a spread of 30 to 90 cm (12 to 35 inches). Fiber crops are sown close and dense, while flower plants want far more room for the air to move.
When to plant
Think of cannabis as a creature of the warm season that has no patience for frost. Start CBD transplants indoors about a month ahead of the last frost, move plants or seed outdoors once the soil holds at least 50°F (10°C) in late spring, and look to late summer for harvest, when shortening days have already called the flowers into being.
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 gather in one of two places: the lower leaves or the heart of the flowers. Read the early signs well and you can step in before a quiet problem travels through a dense planting. Find what matches your garden below, then act while the timing still counts.
Flowers spoiling quietly from within as the season turns damp
This is Botrytis, the gray mold that moves into heavy flowers when the surrounding air goes humid and refuses to stir. It begins deep inside the bud and works outward, so the gray-brown rot has usually done its damage by the time anything shows on the surface. Cut away and dispose of every affected piece, open up the planting so air can travel, 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
Young seedlings collapsing at the soil line in a cold spring bed
This is damping-off, the work of soilborne fungi such as Pythium, Fusarium, and Rhizoctonia that take hold when the ground stays cold and wet underfoot. The stem darkens and turns water-soaked right where it meets the soil, and the seedling tips over without warning. The answer is a warm, well-drained bed sown with clean, treated seed, and a lighter hand with water so the surface never stays soggy.
Fix:
- Improve drainage
- Avoid overwatering
- Plant into warm soil
A summer stand losing its lower leaves to a creeping yellow
When the older leaves down low go pale while the crop is still putting on height, you are looking at nitrogen deficiency, and it turns up readily because hemp is a hungry plant in a season that asks a great deal of it. The fade begins at the bottom and climbs as the plant moves nitrogen toward fresh growth. A tissue or soil test settles the question, after which you side-dress or fertigate to suit the crop and the moment in its cycle.
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 at a distance from animals in the home and garden. Its 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 look into the law where you live before anything is planted.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Severe
Cats take the THC badly. The signs to know are a deep lethargy, an unsteady and uncoordinated walk, vomiting, dilated pupils, a body temperature that drifts downward, and dribbling urine, and a larger dose can carry the animal into seizures or coma.
Dogs Severe
A dog that finds any part of the plant or a dried product turns dull and shaky on its feet, often vomiting, leaking urine, and overreacting to sound and touch. A slow heart rate and a low body temperature tend to follow, and the worst cases reach seizures or coma.
Horses Toxic
Horses answer to the same THC. One that grazes the plant grows sluggish and unsteady, loses interest in feed, and shows a slowed heart rate alongside plain depression.
Rabbits Toxic
There is no harmless nibble for a rabbit. The THC acts on them as it does on other mammals, leaving them dull, off balance, and sluggish, so every part of the plant belongs well out of reach.
Livestock Caution
Cattle, goats, and sheep usually pass over the bitter plant, but any animal that does eat it can turn lethargic and unsteady on the THC. Fence the stock away from a planting and leave nothing to chance.
Birds Caution
Pet birds are small and easily affected, so even a trace of plant material or smoke can leave them dull and off balance. Keep it firmly off-limits.
People Caution
The THC in the plant is psychoactive and intoxicating, and it runs stronger in marijuana types than in low-THC hemp. Growing it is legally restricted in many places, so look into the law 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 are bred for very different purposes, from fiber and grain through to high-CBD flower. These three trace the range worth keeping in mind.
Fedora 17
A monoecious French cultivar grown for fiber and grain, prized for its low THC and for the even stand it brings up across a field.
Futura 75
A dioecious dual-purpose variety planted widely across Europe, valued where a single crop has to serve both fiber and grain.
Cherry Wine
A photoperiod CBD type chosen for its high cannabidiol, all while keeping THC inside legal limits.
How to propagate
Cannabis takes readily to seed for a field planting, and to cuttings when the aim is an exact copy 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 is the customary path for fiber and grain crops. Direct sow once the frost has passed and the soil has warmed, and the seedlings break ground in 7 to 14 days. A start from seed brings genetic variability and the mix of male and female plants that makes up a dioecious stand.
Stem cuttingsModerate
Take cuttings from vegetative mother plants before flowering · 2 to 3 weeks to root
Cuttings are the route CBD and floral growers take to copy a favored plant exactly. Take them from vegetative mother plants before flowering sets in, and they put down roots in 2 to 3 weeks as uniform, high-cannabinoid females that mirror the parent.
Myths
Industrial hemp will leave you intoxicated the way marijuana does.
The law defines hemp as Cannabis sativa carrying no more than 0.3 percent delta-9 THC. That is far too little to bring on any high, which is precisely where the legal line is drawn.
Hemp and marijuana belong to two separate plant species.
They are one and the same species, Cannabis sativa. What separates them is a legal threshold set by THC concentration, not any botanical distance between two different plants.