The distinct leaf of cannabis sativa.
How to Start Growing a Weed Plant From Seed
Are you curious about how cannabis grows? An annual herb, often called a weed, it’s been cultivated since the earliest human civilizations for fiber, food, and wellness. Cannabis thrives with lots of light and proper care—similar to basil or tomatoes. Our growing guide explains how to plant, grow, and harvest this crop.
Cannabis is a flowering herb valued for its distinct aroma and beneficial properties. Growing wild as a weed in many parts of the world, the plant has many therapeutic uses that have been known for centuries, based on ancient texts from Indian Hindus, Assyrians, Greeks, and Romans, as well as in the Judaic religion during the time of Jesus.
Throughout this guide, we’ll use the term cannabis—the legal, horticultural, and medicinal name of the plant. “Weed” and “herb” are everyday slang, while “hemp” generally refers specifically to its fiber and food applications.
How Do You Grow Cannabis (Weed)?
Cannabis grows like other annual herbs but has specific nutrient and light requirements. Its dense flowers need extra care as they mature to ensure a successful yield. Once fully developed, they must be properly dried and cured. Depending on the variety and climate, cannabis is typically planted in early spring and harvested between late September and October.
The two most known species of cannabis are Cannabis sativa and C. indica. There are three seed types: regular, feminized, and autoflowering. As with most plants, you can choose to grow indoors or outdoors. These variables will influence the length of your growing season, ranging from 3 to 8 months, typically 5 to 6. Learn more about selecting and sourcing cannabis seeds in the Varieties section below.
Is Cannabis Legal?
As laws and attitudes shift, cannabis is legal for medicinal use in Canada and 47 U.S. states as of this writing. This has sparked interest in home growing, much like other herbs and useful plants. However, not all states allow home cultivation; consult local laws governing the number of plants allowed and rules on visibility and access.
Planting
Cannabis shares similar nutrient and soil requirements with tomatoes, so if you’ve grown tomatoes successfully, cannabis should feel familiar. Choose a spot with full sun (6 to 12 hours of direct sunlight), good airflow, and some wind protection (such as fencing, walls, or shrubs).
Like most crops, cannabis thrives in light, loamy soil with good drainage and moisture retention. A standard mix is 40% silt, 40% sand, and 20% clay, with an ideal pH of 6.0 (acceptable range: 5.8–6.3). Get a soil test to find out your soil pH.
If you’re fretting about the quality of your native soil, it can be improved with compost and amendments like worm castings to provide long-term nutrients.
When Do You Plant Weed?
Your planting timeline depends on your growing method—whether you start seeds indoors, grow entirely indoors, or plant outdoors. Beginning seeds indoors is common in colder climates since early spring may be too chilly for outdoor growth, just as we commonly start tomatoes indoors.
- Growing 100% Indoors:
Start seeds in late winter or early spring (February–March). Note that you’ll need to provide at least 18 hours of light daily. Grow lights are recommended. See the information below about grow lights. - Starting Seeds Indoors (to Transition Outdoors)
Start seeds indoors 4 to 6 weeks before the last frost date to ensure your seedlings are robust enough to survive outdoors. Again, grow lights are recommended. Solar-powered garden string lights can also be an affordable alternative. - Direct Sowing or Transplanting Outdoors
Plant after the last frost when nighttime temperatures consistently stay above 55°F (13°C), ideally 3 to 4 weeks before the summer solstice. This timing allows plants to acclimate gradually to natural daylight without triggering early flowering, as most cannabis strains begin flowering when daylight hours decrease after the solstice.
Before transitioning any vegetable or herb seedling from indoor to outdoor conditions, remember to “harden off” your seedlings for 1 to 2 weeks, bringing plants outside slowly—a little more each day. Learn more below.
Growing Weed Indoors vs. Outdoors
There’s no single best way to grow cannabis—both indoor and outdoor cultivation have pros and cons.
- Outdoor growing exposes plants to pests and extreme weather, whereas indoor growing gives you control over lighting and the environment. Also, some seed types have a growing season that is too long to allow outdoor seeding and harvesting before the frost.
- But no indoor setup can fully replicate nature. With more space, outdoor plants typically yield larger harvests—hence the saying, “Bigger roots, bigger fruits.” Additionally, outdoor conditions enhance flavor, aroma, and medicinal benefits.
We recommend starting outdoors for those eager to truly learn from the plant. Planting outside requires significantly lower setup costs and showcases the plant’s natural potential. Another option is to grow in containers, which offers flexibility and allows plants to be moved indoors when needed for protection.
| Pros | Cons |
|---|---|
| Low cost (free sun and rain) | Vulnerable to pests, mold, animals, or theft |
| Natural terpene expression | Weather can ruin yields (hail, drought, heatwaves) |
| No need for grow lights or timers | Less environmental control |
| Big plant potential (huge yields in-ground) | Long grow time (can’t rush nature) |
Germinating Cannabis Seeds
Once you obtain your seeds, you’ll need the roots to sprout. There are three methods:
- Soaking in Water: Place seeds in a glass of warm, clean water until the taproot emerges (1 to 2 cm).
- Direct Planting: Sow seeds directly into the growing medium.
- Paper Towel Method: Wrap seeds in a damp paper towel and place them in a sealed ziplock bag or container. Keep them moist (not wet) in a warm, dark place (e.g., a cupboard) for 24 to 120 hours. This method is favored by home growers for its controlled environment.
Tip: To speed up germination and prevent disease, soak seeds overnight in a 1:8 mix of 3% hydrogen peroxide and water.
Once your seed has sprouted, it’s ready to grow!
Growing
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.
Cannabis Plant Stages
1. Germination Stage (1 to 10 Days)
Once your seed has sprouted, transplant it into loamy soil, either in the ground or in containers. You can also use pre-mixed organic soil for cannabis and vegetables.
How to Plant:
- Position the taproot downward, with the seed head just below the surface (1 to 2 cm deep).
- Handle gently—use tweezers to avoid damaging the delicate root.
- Keep the soil moist but not waterlogged.
Light and Environment
Cannabis seedlings need plenty of light to thrive. Most strains are long-day plants, meaning they start flowering as daylight decreases after the summer solstice.
- Growing Indoors: Provide at least 18 hours of light using a full-spectrum bulb with moderate PPFD (100–300 µmol/m²/s). See more information about grow lights below.
- Temperature: Keep between 70°–85°F (21°–29°C).
- Humidity: Seedlings need high humidity. Use a humidity dome or plastic cover until true leaves appear.
For outdoor growers (after the last frost), a row cover or clear tote can protect young plants while maintaining humidity. Early seedlings benefit from partial sun or indirect light to prevent damage, while a shade cloth can shield them from intense sun as they establish.
2. Seedling Stage (2 to 3 Weeks)
The seedling stage begins when the cotyledons emerge; these are the first round leaves.
At the seedling stage, cannabis needs 18 hours of light daily.
Indoor Seedlings:
- Use low-intensity light—dim if possible or adjust the fixture height to prevent light stress. With grow lights, that means 200–300 μmol/m²/s.
- Maintain 65–70% humidity and 65°–80°F (18°–25°C) for healthy growth with a humidifier.
Outdoor Seedlings:
- Indirect sunlight is ideal early on.
- Outdoor growth allows plants to reach their full potential without costly equipment. If you have a sunny spot, take advantage of free sunlight!
The seedling stage lasts 2 to 3 weeks, and once serrated true leaves develop, the plant transitions to the vegetative stage!
3. Vegetative Stage: 3 to 15 Weeks
During the vegetative stage, your cannabis plants develop multiple sets of true leaves and require increased nutrients and light intensity.
Nutritional Requirements:
- Nitrogen (N): Essential for robust stem and leaf growth
- Phosphorus (P) and Potassium (K): Support overall plant health
A nutrient ratio of 3:1:2 (N:P:K) is optimal during this phase. Nitrogen-rich amendments, such as fish emulsion, are beneficial. Many nutrient companies offer formulations tailored for the vegetative stage.
Lighting Requirements:
- Indoor Cultivation: Provide 18 hours of light daily with a Photosynthetic Photon Flux Density (PPFD) around 600 µmol/m²/s.
- Outdoor Cultivation: Ensure plants receive full sun exposure. Wait to transfer plants from the inside to the outside when you are 3 to 4 weeks before the summer solstice. Insufficient daylight (13–15 hours) can stress plants and trigger early flowering. To help reduce shock, you can also reduce grow light time by about 15 minutes per day until you reach 16 hours daily.
When transplanting, don’t forget to harden off! Over 7–10 days, gradually expose plants to outdoor conditions, starting with a few hours of indirect sunlight and increasing daily.
Once outside, give plants plenty of water (about a liter daily). The soil should be moist, not waterlogged or dry.
Pruning and Training:
- Pruning: Encourages branching and increases potential flowering sites.
- Selective Leaf Removal: Like tomatoes, some leaf removal enhances air circulation and light penetration. Avoid excessive defoliation, as larger fan leaves are vital for energy production.
4. Flowering: 6 to 8 Weeks
Outdoors, cannabis plants naturally begin flowering in late summer (August to September). Indoors, flowering is triggered by reducing light hours to 12 hours daily. Cannabis plants fall into two categories:
- Photoperiodic: Require a decrease in light hours to initiate flowering.
- Autoflowering: Begin flowering based on age, usually around 5 to 6 weeks.
Indoors, after light reduction, plants may double in size. Outdoors, the change in daylight hours is more gradual.
During flowering, nutrient needs shift as the plant focuses on bud and flower development. Cut back on nitrogen now, and give flowers a “PK booster” with phosphorus and potassium. If you’re buying fertilizer, look for an NPK ratio of 1:3:2. Or, organic options like kelp meal or bat guano are good choices. You can also find bottled “grow” and “bloom” nutrients to apply every 1 to 2 weeks.
In the outdoors, adding silica helps strengthen cell walls, making plants more resistant to temperature extremes and pathogens. Mulching aids water retention in the root zone, and using shade or frost cloth can protect plants from harsh conditions.
You might notice some bigger fan leaves yellowing, especially at the bottom of the plant: This is normal at the end of the plant’s lifecycle. You can trim these off during the flowering stage; it leads to better yields.
| 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 |
Grow Lights for Cannabis
Whether starting with a small 2x2-foot plant area or setting up a dedicated grow room, choosing the right grow light—and using it correctly—is crucial. Full-spectrum LED lights mimic natural sunlight, supporting your plants through their entire life cycle with just one fixture. They’re cost-effective, offering lower energy usage and better heat efficiency. Most importantly, LEDs help produce healthier plants and higher yields.
Good LED lights provide the specific wavelengths cannabis plants need at different growth stages:
- Blue light (400–500nm): Supports vegetative growth
- Red light (600–700nm): Promotes flowering and budding
When choosing an LED grow light, focus not just on wattage but also on its coverage area:
For a 4x4-foot area with 4 to 6 medium plants, you’ll need at least 600 to 800 watts of LED power. Check the PPFD (Photosynthetic Photon Flux Density) and PAR maps provided by manufacturers to ensure even light distribution. Use programmable timers to automate light cycles for consistency.
How to Set Up LED Grow Lights
Height Adjustment
- Seedling stage: Keep LEDs at 24–30 inches above your plant canopy.
- Vegetative stage: Drop to 18–24 inches for more intensity.
- Flowering stage: Maintain 12–18 inches, depending on the light’s strength.
Always check the manufacturer’s recommendations, as high-intensity LEDs can scorch plants if placed too close.
Selecting and Sourcing Seed
For cannabis seeds, choose reputable breeders! Get insights from online communities like social media groups and forums on where to obtain top-quality seeds.
Three Types of Cannabis
Cannabis has three main species, often called “strains” within the Cannabis genus: C. sativa, C. indica, and C. ruderalis.
- C. sativa: Native to equatorial regions worldwide, C. sativa plants are tall (10 to 20 feet) with narrow leaves, ideal for outdoor growing. They have long flowering times (10 to 16 weeks) and a higher THC-to-CBD ratio and are often used medicinally for depression, fatigue, and focus.
- Popular strains: ‘Sour Diesel’, ‘Jack Herer’, ‘Durban’
- C. indica: From the Hindu Kush Mountains, Indica is shorter (2–6 feet), with broad leaves and dense buds. It has a faster flowering time (7–10 weeks) and is perfect for indoor growing. C. indica is high in CBD, offering sedative effects for insomnia, pain, and relaxation.
- Popular strains: ‘Granddaddy Purple’, ‘Northern Lights’, ‘Bubba Kush’
- C. ruderalis: A small, hardy strain from harsh climates near the Poles (Eastern Europe, Siberia), C. ruderalis is autoflowering, completing its cycle in 8–10 weeks. It has low THC but higher CBD, making it useful for medicinal purposes and often bred with C. sativa for autoflowering varieties.
- Popular strains: ‘Lowryder’, ‘Auto Northern Lights’, ‘Auto Blueberry’
Modern cannabis strains are often hybrids, balancing effects and benefits. Understanding their flowering cycles and harvest times is key.
Types of Seeds
There are three main types of seeds: autoflowering, regular, and feminized.
- Autoflowering Seeds: Ideal for beginners, these plants complete their cycle in 8–10 weeks, regardless of light exposure, and are small, perfect for limited space.
- Regular Seeds: These result from natural male-female crosses, producing a 50/50 ratio of male and female plants. Males contribute to genetic diversity but don’t yield consumable flowers.
- Feminized Seeds: Produced by stressing a female plant, these seeds result in almost entirely female plants, offering convenience as only females produce consumable flowers.
Understanding Cannabis Sex and Pollination
Cannabis is dioecious, meaning male and female flowers grow on separate plants. Identifying plant sex early is crucial, as male plants must be removed before they pollinate females. Only females produce buds, but males are essential for breeding. Outdoors, sex is typically visible in early flowering, though genetic tests or controlled indoor flips can identify it earlier.
Pollination results in seed production, lowering the final product’s quality. Unless growing only female clones or feminized seeds (which produce only females), monitor plants daily as they transition from vegetative to flowering stages.
How to Identify Male and Female Plants
Male flowers appear as small round buds at the plant’s nodes and develop into clusters that release pollen, which can travel miles. Remove males as soon as identified to prevent pollination.
Both male and female flowers start as small spheres at the nodes, just behind the stipules. Over time, they differentiate:
- Female flowers: A narrow tip from which a hair-like “style” or “pistil” emerges
- Male flowers: Rounder with no narrowed tip or pistil
Recognizing these differences ensures a seed-free, high-quality harvest.
Harvesting
Harvesting is the most crucial step, as improper drying or ventilation can ruin even the best crop. Plan ahead for harvesting, drying, and storing, ensuring you have enough space to hang and dry your crop indoors.
Timing the Harvest
Harvesting typically occurs in September or October. Monitor trichomes for maturation (see picture of female plant above). Trichomes are tiny, filament-like growths that resemble minuscule crystals on the flowers, leaves, and stems. As the pistils (hairs) on the plant darken to orange, use a magnifying glass or jeweler’s loupe to check the trichomes.
When the trichomes turn from clear to milky white and finally amber, it’s time to harvest! Some gardeners way to aim for an 80/20 mix of cloudy to amber.
Optional: As the trichomes turn amber, some gardeners will do a “flush” watering to remove the nutrients from the plant. Saturate your plants with 2 to 3 liters of water. Let the plant dry out (2 to 3 days). Then, repeat a couple more times until you’re about a week from harvest.
How to Harvest
Most gardeners harvest the plant by cutting the entire plant at once. With clean gardening sheers, chop off the main stalk close to the soil level, keeping the buds attached to the stems. This tends to work best with smaller plants.
Some gardeners will harvest in stages, as the buds at the top of the plant (which get more light) mature faster. In this case, you can cut the stems from the top half of your plant. Look to the central stalk and the crotch where two branches come together and cut off each side stem; leave an angle, which makes drying easier.
After you cut down the plant stems, trim off the leaves. Some gardeners trim after the plant dries, but it’s probably easier for beginners to trim now (wet trim) since all of the leaves are visible (before some curl up). Try NOT to touch the buds.
We advise wearing gardening gloves for harvesting. Sometimes, the gardening sheers will get sticky. You can clean them with a sponge or paper towel with isopropyl alcohol to keep them sanitized.
Drying Cannabis (5 to 14) days.
Hang the plants upside down from a clothesline or hanger. It’s essential to dry out the moisture in the plant to preserve aroma, smoothness, and potency.
As with drying any kind of herb, you’ll need a dark place with lots of airflow (or you can use a gentle oscillating fan). Temperature should be 60°–70°F (15°–21°C) and humidity at 50–60%.
The plant is properly dried when the stem snaps cleanly, and the buds feel dry outside while remaining slightly sticky inside. Avoid drying too quickly (which causes harshness) or too slowly (which risks mold).
The buds should easily separate from their stems, like a tomato when it’s ripe on the vine. If you pull a bud from the stalk and some other fibers come with it, it’s not dry enough.
Curing Cannabis (2 to 3 weeks)
The final stage is curing your harvested buds. Curing draws out most of the remaining moisture. It enhances taste, texture, and aroma. We tend to use glass jars, such as large mason jars. They must have an airtight seal. Drop the dried buds into the container, leaving about an inch at the top. Space the buds loosely so they have plenty of air.
If you are using glass jars, you need to control humidity. For beginners, we recommend adding a tiny humidity pack like this. (Another option is a hygrometer to maintain humidity around 55–65%.)
During the first week, open the container daily to release a little air and moisture. This is called “burping.” For the next 2 to 3 weeks, burp every few days. Note: If the scent is moldy when you open the jars, that’s not good! It should smell a little sweet. You may be able to save your harvest if you leave the lids off for an entire day to release more moisture. Then try again.
Storing Cannabis
You’re done! Store your jars in a dark, dry, cool place like a cupboard or drawer. If your cannabis buds are stored in an airtight jar properly, your harvest should keep its quality between 12 and 18 months.
Congratulations! Enjoy your harvest! You’ve not only learned how to grow cannabis, but you’ve probably discovered a lot more about being a good gardener—from soil pH to sunlight, patience to precision. Keep experimenting, keep learning, and most of all, enjoy your homegrown success.
Melissa Moore
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