Planting, Growing, and Harvesting Cannabis Plants
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The valuable properties of cannabis have been known for centuries. From fiber to food to medicine, these benefits have led to the worldwide cultivation of this annual flowering herb. Are you interested in adding these plants to your garden? This guide aims to streamline the growing process by focusing on growing cannabis from seed. Here is how to get started.
About Cannabis
Human fascination with flowering plants has endured through the ages, driven by their beauty and fragrance. Cannabis, while not possessing the visual appeal, has captivated human interest due to its distinct aroma and medicinal properties.
With recent shifts in cultural attitudes and laws (with restrictions) now allowing for home cultivation throughout Canada and many parts of the United States, more people have become interested in how to grow this once-taboo plant.
Cannabis is similar to other annual herbs, with slight differences in nutrient and light requirements. The dense flowers need extra care as they mature, or all of your hard work may be ruined. Once fully mature, flowers must be dried and cured correctly to achieve a quality end product.
Female Vs. Male Cannabis Plants
Cannabis is dioecious, meaning that male and female flowers are present on different plants. Identifying plant sex is essential because males need to be removed before they can pollinate the females. If pollination occurs, seeds develop, diminishing the final product’s quality. Unless you’ve grown only female clones or feminized seeds (seeds bred to produce only female plants), you’ll need to prevent this by observing plants daily as they transition from the vegetative stage to budding and flowering.
After the first male flower arrives, more roundish flowers will appear at the base, forming a cluster. In time, the male flowers will open and release pollen. Pollen can travel for miles in the wind. It’s very important to remove male plants from the garden when they are first identified!
How to Identify Male and Female Plants: Male and female flowers first appear as spheres in the node of the plant (where a leaf, bud, or branch attaches to a stem), behind the stipules (tiny, pointed, leaflike appendages at the base of the leafstalk).
The female flower takes the shape of a claw, with a tip that comes to a narrow point. A male flower is more rounded, without a narrowed end. On females, a hairlike appendage emerges from the narrow point of the young flower. This is called a “style” and is often referred to by cannabis growers as the “pistil.”
Growing
Where to Grow Cannabis
Growing cannabis can be as simple or complex as you wish. When growing outdoors, you can succeed with loamy soil, sunshine, water, and fertilizer. Growing outdoors typically provides higher yields and a greater depth of flavor in the finished product.
Whether in the ground or in large containers, plants have more space to grow, and many experts agree that environmental pressures encountered outdoors push a plant to produce a more complex balance of terpenes, which provide taste, aroma, and medicinal benefits.
However, growing outdoors can make your cannabis vulnerable to pests, extreme weather, or even theft. Planting in containers allows you to bring cannabis indoors when needed for protection. When selecting where to grow your plants, consult local laws governing the number of plants allowed and rules on visibility and access.
The Four Stages of Cannabis Growth
Cannabis cultivation, like all flowering plants, progresses through four key life stages: germination, seedling, vegetative, and flowering. Understanding and managing the care requirements at each stage is essential for a successful harvest.
Germination: 1 to 10 Days
In most zones, you will want to start seedlings indoors in the late winter. Water seedlings and provide at least 18 hours of light. During the vegetative state, plants grow substantially in size. By June 1, it’s time to move plants outside in most zones.
Effective germination is crucial for a healthy cannabis plant. Before planting, it is advisable to disinfect the seeds by soaking them in a 3% hydrogen peroxide solution for 3 to 5 minutes. To speed up germination rates, mix 3% hydrogen peroxide and water at a 1:8 ratio and soak overnight. Successful germination requires both moisture and warmth. Maintain moisture by wrapping seeds in a damp paper towel, or placing them in water. Once the tap root emerges, transfer the seed to well-draining growing media, ensuring it remains moist, but not waterlogged. You can also sow seeds directly into the growing media.
Cannabis likes loamy and light soil with good drainage and water retention. Many growers swear by a 40/40/20 combination of silt, sand, and clay. Learn how to improve your soil with soil amendments.
Seedling: 10 to 14 Days
The seedling stage commences when the stem and cotyledons (the initial round leaves) emerge. At this point, the plant requires lighting, although not excessively. A full-spectrum lightbulb providing a Photosynthetic Photon Flux Density (PPFD) of 100-300 for 18 hours daily is sufficient. Given the seedling’s limited root structure, maintain humidity levels between 65 to 70% and temperatures between 65-80°F (18-25°C) to support healthy growth.
Vegetative: 3 to 16 Weeks
Upon developing serrated true leaves, the plant enters the vegetative stage. This phase involves increased nutrient feeding and light intensity. Recommended lighting is 18 hours with a PPFD around 600. During this stage, a nutrient ratio of 3:1:2 (NPK) is optimal. Cultivators can also manipulate plant structure by pruning or topping, which promotes branching and more flowering sites. Selective leaf removal can enhance air circulation and light penetration, but avoid excessive defoliation as larger fan leaves are vital for the plant’s energy.
Flowering: 6 to 8 Weeks
The flowering stage is triggered by reduced light hours and plant age. Cannabis plants fall into two categories: photoperiodic and autoflowering. Photoperiodic plants require a decrease in light hours to initiate flowering, while autoflowers begin to flower based on age, typically around 5-6 weeks. Nutrient requirements shift during this phase, with a reduced need for nitrogen and increased demand for phosphorus, reflected in an NPK ratio of 1:3:2.
Providing optimal environmental conditions—temperature, humidity, and lighting—throughout each growth stage is fundamental for achieving a bountiful and high-quality cannabis harvest.
| Life Cycle | Optimal Lighting Length and PPFD | Optimal Temperature | Optimal Humidity | Optimal Nutrients NPK ratio | Notes |
|---|---|---|---|---|---|
| Germination | No light needed | 70-85 F 21-28 C | 70-90% | No nutrients needed | Temperature and moisture are the most important |
| Seedling | 18 hours 100-300 µMol/m2/S | 74-78 F 23-26 C | 60-80% | No nutrients needed for soil. Diluted 3:1:1 for inert media | Keep humidity high and intensity of light at low to medium. |
| Vegetative | 18 hours 400-600 µMol/m2/S | 70-85 F 21-28 C | 55-70% | 3:1:2 | Pruning stage, pest management. Watch for nutrient deficiencies and toxicities. |
| Flowering | 12 hours 600-1000 µMol/m2/S | 65-80 F 18-27 C | 35-55% | Early 1:3:2 Late 0:3:3 | Watch for mold and pests. Trellis plants. Defoliate and lollipop if desired |
The Importance of Light
Most cannabis strains are long-day plants, meaning that the plant will enter the flowering stage when the days begin to shorten following the summer solstice. Growers desiring large yields start seedlings inside in late winter and provide at least 18 hours of light—usually a combination of natural and artificial—until the last frost, after which the plants can be placed outside.
However, plants that are started indoors under 18-plus hours of light may receive only 13 to 15 hours of daylight once moved outdoors, depending on location, which can cause stress and temporarily prompt the plant to enter the flowering stage. To prevent this, plant plants should be permanently planted outside a little later in spring, 3 to 4 weeks before the summer solstice.
You could also use supplemental lighting outside to extend light hours or break up the dark cycle by bringing the plants inside at sunset to be placed under lights. Learn more about the benefits of grow lights.
Fertilizing Cannabis
Nutrient requirements for the vegetation and flowering stages differ. To support the growth that occurs during the vegetative stage, high amounts of nitrogen and phosphorus are needed. During the flowering stage, growth slows as the plant concentrates on developing buds and building flowers. At this time, the grower should reduce nitrogen and increase potassium to aid the plant in flower development. Nutrient companies create perfect solutions for both the vegetative and bloom stages, usually labeled as such.
A grower should be on the lookout for toxicities and nutrient deficiencies. One of the most common issues is too much or too little nitrogen. If lower leaves are yellowing, nitrogen is most often needed. If the leaves turn a glossy dark green and curl under, then most likely, the plant has too much nitrogen. Watering with no nutrient supplement—a process known as “flushing”—would then be required.
Harvesting
The most crucial step in growing cannabis occurs at the end of the process when it’s time to harvest and dry the flowers. You can produce high-quality cannabis and then destroy it in the last steps by drying it too quickly or not providing enough ventilation.
A grower needs to plan well in advance for harvesting, drying, and storing. You’ll need enough space to hang and dry your crop— essentially, an area that matches the size of your cultivation plot. Drying your harvested flowers slowly ensures a smooth and aromatic product.
Harvesting Cannabis
Once flowers form and the pistils darken, it’s time to check more closely for maturation. Using a phone camera, magnifying glass, or jeweler’s loupe at 30x magnification, you can see the trichomes, which look like tiny hairs on the flower. They will be transparent at first and then become clouded. When they are milky white, it’s time to harvest.
Cut plants at the stem and hang them upside down in a dark, dry, well-ventilated location. Trim as much green leafy matter from the flowers as possible. It’s best to dry cannabis in an environment that provides 60 percent relative humidity and a temperature of at least 60°F (15°C).
Drying the plant material takes from 5 to 7 days up to 2 weeks. Test for dryness by bending a stem; when it snaps, it’s ready.
Curing Cannabis
Curing is a preservation technique that removes moisture and renders a more shelf-stable herb. After drying your cannabis, remove any remaining fan leaves and move cannabis into closed containers. Periodically open containers to remove moisture and promote curing, which commonly takes 3 to 8 weeks—although some growers cure their crop for up to 6 months.
This initiates metabolic processes that change the chemical components of the cannabis plant to promote a smooth smoke. After a few weeks, the time between airings should be lengthened, while that of the airings themselves should be shortened.
Storing Cannabis
To store cannabis properly and reduce the degradation of cannabinoids and terpenes, place it in an airtight container out of direct sunlight. A hygrometer is used to measure relative humidity inside the container, maintaining it at around 55 to 65 percent.
Melissa Moore
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