Herb · Cannabaceae
Cannabis / Hemp
Cannabis sativa
Offer it full sun, warm soil, and steady nitrogen, and Cannabis sativa will reward you, racing from seed to harvest in 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 grows from a single seed into a tall stand of stems in just one season, and that vigor makes it forgiving company for a new grower. 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 separate plants but two ends of one species, sorted simply by how much THC the flowers hold.
How you grow it really depends on what you hope to get from it, so there is no single right way to do this. Fiber and grain crops go in thick and stay unpruned, racing up to 4 m (157 inches) in good ground. Plants grown for CBD or flower are given more room, a topping or two, and their lower branches cleared so light and air can reach the buds.
Whatever you are growing it for, the plant asks for the same comforting basics: full sun, warm well-drained soil, and plenty of nitrogen. It flowers when the days grow short in late summer, and that natural rhythm sets your harvest clock for you. The one thing to settle before you plant is the law, since growing Cannabis sativa is restricted in many places.
Care
The short version: give it full sun and deep, well-drained soil that you keep evenly moist without ever letting it waterlog, feed it generously with a nitrogen-forward mix through the vegetative stretch, and you can carry it gently from spring planting all the way to a late-summer harvest.
Light
Cannabis loves full sun, and the more direct hours you can give it, the happier it will be. It will manage in partial sun, but shorter light trims both the fiber yield and the strength of the flowers, so an open, unshaded spot is the kindest place for it.
Water
Keep the soil evenly moist without ever letting it sit wet, since waterlogged ground invites root disease. A field crop drinks roughly 25 to 30 inches of water over the season, with its thirstiest stretch during establishment and the vegetative push, and once you settle into that rhythm it becomes second nature.
Soil
Plant it in deep, well-drained loam that is rich in organic matter, with the kind of aeration that lets the roots run freely. A pH between 6.0 and 7.5 suits it nicely, and good drainage matters every bit as much as fertility here.
Temperature
The plant is at its best from 59°F to 86°F (15°C to 30°C). It needs real warmth to get going and has no tolerance for frost at all, so simply wait for settled spring weather before it goes out, and you will be off to a strong start.
Humidity
Somewhere around 40% to 70% is the comfortable range. The one thing to watch is humidity that climbs and lingers inside a thick canopy, since damp, still air is exactly what lets bud mold take hold, so a little airflow goes a long way.
Feeding
This is a heavy nitrogen feeder, often wanting 100 to 150 lb of nitrogen per acre depending on what you are growing it for. Feed through the vegetative season with a nitrogen-forward balanced fertilizer, matching the rate to whether you are after fiber, grain, or flower, and the plant will tell you it is well fed.
Pruning
Fiber and grain crops are left to their own devices and never pruned, which keeps things simple. For CBD and flower production, top the plants and gently strip the lower branches so air moves freely and light reaches deeper into the canopy.
Repotting
As an annual field crop it is not repotted, so there is little to fuss over. CBD starts get one transplant out of the plug tray after hardening off, and from there they settle into the ground for the rest of the season.
Size & spacing
Plants run from 1 to 4 m (39 to 157 inches) tall depending on the type and how thickly you sow them, with a spread of 30 to 90 cm (12 to 35 inches). Fiber crops go in dense and close, while flower plants appreciate far more elbow room for airflow.
When to plant
Cannabis is a warm-season annual that simply will not tolerate frost, so let the calendar guide you. Sow your CBD transplants indoors about a month before the last frost, set plants or seed out once the soil has reached at least 50°F (10°C) in late spring, and look forward to harvesting from late summer once the shortening days have nudged the plant into flower.
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
Almost every hiccup with this crop shows up in one of two places: the lower leaves or deep inside the flowers. The reassuring part is that if you catch the early signs, you can step in well before a small issue spreads through a dense stand. Match what you are seeing to the notes below, then act while your help still counts.
Thick buds turning gray-brown and soft from within
This one is Botrytis, the gray mold that quietly moves into heavy flowers when the air stays humid and still. It begins deep inside the bud and works outward, so the fuzzy gray surface you finally notice means it has been busy for a while. Don't panic. Cut away and destroy anything affected, open the canopy so air can move, and bring in the crop as soon as it is ready, and you can save the rest of your harvest.
Fix:
- Remove and destroy infected material
- Increase airflow and reduce canopy density
- Harvest promptly when mature
Tiny seedlings pinching at the soil line and tipping over
Losing seedlings this way stings, but it has a clear cause: damping-off from soilborne fungi such as Pythium, Fusarium, and Rhizoctonia, which take hold in cold, wet ground. The stem goes dark and water-soaked right where it meets the soil, and the little plant simply falls. The good news is that prevention is easy. Sow into warm, well-drained beds with clean, treated seed, and ease back on the water so the surface never stays soggy.
Fix:
- Improve drainage
- Avoid overwatering
- Plant into warm soil
Older leaves softening to yellow while the plant keeps climbing
Take a breath, because this is almost always just nitrogen deficiency, and it turns up a lot since hemp eats so hungrily. The plant pulls nitrogen from its oldest leaves to feed the fresh growth up top, so the pale tone starts low and creeps upward. A simple tissue or soil test will confirm it, and once you side-dress or fertigate to suit your crop and stage, the plant recovers and presses on.
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 gently but firmly away from animals. 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 do check the law where you live before you plant.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Severe
Cats take the THC harder than most. You may notice deep lethargy, a wobbly and uncoordinated walk, vomiting, dilated pupils, a dropping body temperature, and dribbling urine, and at higher doses the picture can turn into seizures or coma.
Dogs Severe
A dog that gets into any part of the plant or a dried product will seem dull and unsteady on its feet, often vomiting, leaking urine, and flinching at sound and touch. A slow heart rate and a low body temperature come up often, and the most severe cases can bring seizures or coma.
Horses Toxic
Horses feel that same THC. A horse that grazes the plant grows sluggish and unsteady, often loses interest in feed, and shows a slowed heart rate alongside clear depression.
Rabbits Toxic
There is no safe nibble for a rabbit. The THC works on them much as it does on other mammals, leaving them dull, off-balance, and sluggish, so it helps to keep every part of the plant well out of reach.
Livestock Caution
Cattle, goats, and sheep usually steer clear of the bitter plant on their own, yet an animal that does eat it can turn lethargic and unsteady from the THC. Fencing stock away from any planting keeps everyone safe.
Birds Caution
Pet birds are small and sensitive, so even a little plant material or smoke can leave them dull and off balance. The kindest choice is to treat it as off-limits.
People Caution
The plant's THC is psychoactive and intoxicating, and it runs stronger in marijuana types than in low-THC hemp. Cultivation is legally restricted in many places, so it pays to check the laws where you live, and to 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 jobs, from fiber and grain all the way to high-CBD flower. These three give you a clear sense of the range worth knowing.
Fedora 17
A monoecious French fiber and grain cultivar prized for its low THC and for the even, reliable stands it puts up.
Futura 75
A dioecious dual-purpose variety that growers across Europe trust for both fiber and grain.
Cherry Wine
A photoperiod CBD type chosen for its high cannabidiol while keeping THC within legal limits.
How to propagate
Cannabis takes happily from seed for field crops, or from cuttings when you want exact copies of a plant you have come to love.
SeedEasy
Direct sow after last frost into warm soil for fiber and grain crops · 7 to 14 days to emergence
Seed is the friendliest path for fiber and grain crops, and it is hard to get wrong. Direct sow after the last frost once the soil has warmed, and you can expect the seedlings to break ground in 7 to 14 days. Starting from seed brings genetic variability and the natural mix of male and female plants in 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 copy their finest plants, and the method is well within reach with a little patience. Take them from vegetative mother plants before flowering starts, and they root in 2 to 3 weeks into uniform, high-cannabinoid females that mirror the parent.
Myths
Industrial hemp will get you high like marijuana.
You can relax on this one. The law defines hemp as Cannabis sativa carrying no more than 0.3 percent delta-9 THC, and that is far too little to be intoxicating, which is precisely why the line is drawn where it is.
Hemp and marijuana are two different plant species.
Both are the same species, Cannabis sativa. What separates them is a legal line drawn by THC concentration, not any botanical difference between two kinds of plant.