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Cannabis 101

The Sexiest, Smartest, Most Useful Plant in Your Garden

Cannabis grows like—yes!—a weed. Plant the seeds of your own bliss, stress relief, and healing with this cultivation plan from the former editor of Organic Gardening magazine.

A dirty life is a happy life for me. When I was the editor-in-chief of Organic Gardening magazine in the 2000s, I spent my days visiting gardens, overseeing our own extensive test plots, and parsing the pro and cons of squash varieties. I’ve been tending my own beds full of edible, ornamental, and medicinal plants for nearly 30 years, and I can go on for hours about Lycopersicon esculentum (that’s tomato to you). But when I was researching my book, Green Weed—published in 2009 under the pseudonym of Dr. Seymour Kindbud—I discovered that cannabis is sexier, more vigorous, and more awe-inspiring than any other crop I’ve raised. And you don’t have to be a dirt lover—or even an experienced gardener—to grow and harvest a potent batch for yourself. 

Classified Information

Not to flash you back to middle-school science class, but we’re going to start with a bit of useful taxonomy. You may remember the system of classifying living things into a series of increasingly specific categories: Kingdom, Phylum, Class, Order, Family, Genus, Species. We’re going to focus here on the last two. The genus Cannabis has one species, sativa, which has three generally accepted subspecies—sativa, indica, and ruderalis—that differ in a few important ways for growers. Sativa plants reach 5 to 6 feet tall, take longer to grow, and typically bear fewer flowers than indica varieties, which tend to be shorter (under 4 feet) and bushier. Ruderalis is a smaller, weedier plant that produces little THC. Creating new strains of cannabis is relatively easy even for amateurs and many, if not most, popular strains available today are hybrids of sativa and indica. 

The plant known as hemp is Cannabis sativa, too, so it looks and grows just like any other member of the species. But, legally speaking, hemp refers to strains that have less than 0.3% THC. Hemp has long been valued as a source of fiber for rope, T-shirts, and other textiles, and its edible seeds are high in protein and healthy fats. Now farmers are also planting hemp strains that bear CBD-rich flower buds. 

Tip: Tall, sativa-dominant strains are ideal for outdoor growing, where the sky’s the limit. Indicas tend to be shorter, so they’re easier to manage when you’re growing indoors. 

Related: Garden Helpers for Your Budding Marijuana Crop

Seedy Behavior

A cannabis seed doesn’t look like much, but inside the shiny, brown, hard outer coat are the makings of a slow-motion explosion. When a bit of moisture permeates the shell, a tiny embryo—a thin stem and two tiny round leaves—bursts through the coat, unfurls and aims toward the nearest light. Cannabis seeds need only a little water to trigger the sprouting. If you push them into a light soil mix (equal parts peat, perlite, and compost) that you keep consistently damp but never soggy, seedlings will emerge in 7–10 days. The time to plant outdoors is when nighttime air temperatures are consistently at least 60 degrees. 

Plants will do best in sunny, dry conditions but remember: This plant has been a breeding success from Nepal to northern California. It can adapt, just like human beings have. If you buy from local cultivators, they’ll have a strain that works for your area, and loads of advice on how and where to plant. 

When shopping for seeds, you’ll find standard, feminized, and auto-flowering options. Standard seeds are easy to get—you can ask a friend for a few, or order them online, and then save seeds from your own plants year to year. With standard seeds, up to 50% of your plants can be males, which don’t bear any flower buds (more on this coming up). Feminized seeds are more expensive, but they promise all of your plants will be desirable females. Auto-flowering seeds are also feminized, but they’re even easier to care for because they start budding at maturity, so you won’t have to be all finicky about tracking hours of sunlight and such. Blue Dream is known to be widely adapted and resilient in less than ideal growing conditions. So that’ll simplify your quest, as well.

Tip: In most states with legalized recreational use, home growers are free to produce their own supply. Check local legal conditions, just as you’d check rainfall and temperatures. 

Tender Sprouts

The most vulnerable time in a cannabis plant’s life cycle is the sprout stage—from the time it pokes through the soil until it has established roots, about three weeks after planting. Whether you plan to grow your crop outside or inside, you increase its likelihood of survival by starting the seeds indoors in little peat or paper pots and keeping them under ordinary fluorescent lights. Ideal ratio: 18 hours of light, but if that jacks your electricity bill too much, 14 hours may work as well. (You can transplant the seedlings outdoors after the first month, once overnight temperatures reach 60ºF.) The little sprouts are particularly susceptible to a fungal disease that forms on the soil surface called “damping off,” which kills them overnight. Prevent this by setting up a small fan to blow lightly on the sprouts around the clock. To save electricity, turn on the blower only during the dark hours, when fungi proliferate. And sprinkle a pinch of cornmeal (a natural anti-fungal) on top of the soil after the sprouts come up. 

A cannabis seed doesn’t look like much, but inside the shiny, brown, hard outer coat are the makings of a slow-motion explosion.

The cotyledon (say “cot-el-eden”), the technical term for the embryo, is fed by the endosperm, a tiny packet of starch and other nutrients inside the seed. About two weeks after sprouting, the first “true” leaves appear. Unlike the little round leaves that show up first, the new ones have the familiar serrated look of mature cannabis foliage. When you see those new leaves, it’s time to begin feeding the seedlings with a very dilute liquid organic fertilizer, such as compost tea or fish-and-kelp emulsion. A small dose of nutrients—about a quarter of what’s recommended on the label for full-size plants—will help your sprouts without overwhelming them. 

Tip: For the first three weeks, mist sprouts lightly each day for the moisture they need. 

Clone Army

Once your plant begins leafing out, it’s a simple matter to expand your crop through cloning. Clones are more reliable than starting from seeds because clones already have a head start past the sprout stage. Another advantage for clones: You can be sure the new plant will have the same characteristics as the parent plant, including gender. 

But you don’t have to be a mad scientist to make cloning work for you. Simply cut a medium-size leaf and its stem from a large, healthy plant, set the stem in a glass of water or a small pot with damp peat, and wait. The stem will start growing its own roots in 7–10 days—the sign that your cloning was successful. By the way, this process, known as “asexual reproduction,” works for tomato plants and many other garden gems, too. 

If you treat your plant right, you can expect to harvest upwards of a pound of dried bud for your smoking, tincturing, and salving pleasure. 

Tip: Once you find a favorite strain, you can keep a steady supply of new plants going almost indefinitely by taking clones from each generation you grow.

The most vulnerable time in a cannabis plant’s life cycle is the sprout stage—from the time it pokes through the soil until it has established roots about three weeks after planting.

Underground Action

Cannabis plants are “bioaccumulators,” which means they draw heavy metals and other toxins out of the soil. That’s why hemp has been planted in brownfields—abandoned industrial sites that are unfit for any use. Cannabis roots pull the pollutants from the ground and cleanse the soil.

That’s cool for those of us who care about the environment. But cannabis growers—and users—should keep in mind that the chemicals the roots extract from the soil remain in the leaves and buds. Your backyard probably isn’t a toxic waste dump, but it may still contain herbicides, fungicides, and synthetic fertilizers you won’t want to ingest. The chemicals linger in only parts-per-billion amounts, but when the oils in cannabis flowers are concentrated—for vaping, dab, or wax—the toxins come along, too. 

Tip: Choose organic, whether you’re buying fertilizer and pest-control products for your grow or picking up consumable products at a dispensary. 

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Leafing Out

Cannabis plants aren’t magic beanstalks, but once they start growing, you’d better stand back. When raised outside under the summer sun, they can add 2 inches a day in height and width. The leaves form in pairs on opposite sides of the stem and each of the main leaf branches may open up to 10 leaflets along its length. Even under artificial lights, cannabis plants quickly turn into bushy plants. If you’re raising them indoors, raise the light fixtures just about every week during the 10–12 weeks of the plants’ “vegetative” stage. Keep the lights no more than 4–6 inches from the tops of the uppermost leaves to ensure the plants don’t become “leggy,” stretching toward the light with weak stems and sparse foliage. 

Inside or out, cannabis plants during their adolescent stage—from sprout to full-size—are as hungry as your average teenager. Nitrogen is the critical nutrient that plants need to produce sturdy stems and lush foliage. When you buy fertilizer, you’ll see that it comes with an N-P-K rating, which refers to the key nutrients of nitrogen, phosphorus, and potassium. During the vegetative stage, use plant food with a high ratio of nitrogen, such as 10-5-10. And take it easy. Overfeeding is as bad for your plants as it is for you. It always leads to unhealthy, unsustainable growth. Closely follow the guidelines on fertilizer packaging. 

Tip: The best fertilizers get their nitrogen from natural sources, such as guano (bird poop), worm castings (worm poop), fish, or seaweed. 

Related: Cannabis Extraction 101

Battle of the Sexes

Cannabis is a girls’ club: Only females flower. And you’ll need to weed out the males, so they don’t turn all that lovely bud into harsh and useless (for your purposes) seeds. The challenge is in identifying the males before they start releasing, or “shedding,” their pollen. Sexual expression can begin as early as four weeks into the plants’ growth and pollination can happen in just a few hours, so you need to check your crop daily for signs that puberty has begun. 

The male plants grow tiny pairs of ball-shaped sacs (yes, these males have balls, too) in the area where the leaves meet the stems. In the same spot, females produce claw-shaped “pre-flowers” with thin, hair-like “pistils” emerging from their center. Some plants become hermaphrodites, with both balls and pistils—botanists refer to these as “monoecious.” The male and female parts are tiny when they appear, so you may need to use a magnifying lens to distinguish them. Once you’ve confirmed your identification, pull out the male plants, along with any hermaphrodites, and discard them far from the females (the males can still shed pollen after they are uprooted).  

Tip: Feminized seeds and clones rarely produce males, but they can turn into hermaphrodites, so you need to be vigilant to confirm that you have only females.

Blooming Good

Female cannabis plants get in the mood for reproduction in the dark. Or rather, they begin blooming when the nights are longer than the days. This happens naturally outside at the fall equinox (on or about September 22), when the sun is up for fewer than 12 hours each day. Outdoor enthusiasts should plant eight to 10 weeks before the equinox, or in late spring. Indoor growers trigger the start of flowering by managing the on/off cycles of their artificial lights, once their plants are close to mature height. Do everything you can to keep your budding plants completely dark at night. Cannabis plants are so sensitive to light that even the smallest amount—from a flashlight or a streetlight—can disrupt the flowering process. 

A constant supply of carbon dioxide is as important to plants as oxygen is to you. If you grow cannabis inside, be sure to ventilate the room so the leaves get plenty of fresh CO2. A good venting system also helps carry away the potent aroma of the plants when they’re in bloom.  

Tip: To maximize bud growth, switch to plant foods high in phosphorus and potassium about two weeks before the plants begin to bloom. That magic moment comes when they’ll be in darkness more than 10 hours a day—either with sunlight, or because you’re switching off the lights. Look for organic fertilizers that contain bone meal, kelp meal, or other natural sources of these nutrients.

Frustrated Females

Buds—commonly sold as “flower” in dispensaries—are actually tight clusters of dozens of blooms awaiting pollination, which botanists refer to as “bracts.” The tiny flowers wave their pistils in the air, waiting to attract a little pollen from a male plant. They also secrete sticky trichomes to trap any grain of pollen that blows by. That gummy resin is the plant’s most concentrated source of cannabinoids—THC, CBD, and others—and the fragrant essential oils called terpenes. As the plant goes unpollinated, it gets more desperate to mate, producing more flowers and more resin. 

The biggest flower cluster typically forms at the top of the stalk and is known as a “cola.” I’ve seen some that weigh as much as 5 grams—a bit less than a quarter ounce—and credible photos of some that are even bigger. Smaller buds emerge in the joints where the leaf branches meet the stems; the buds’ sizes diminish lower on the stalk because the foliage above them shades them from the light. 

Tip: Judiciously trimming a few of the larger upper leaves can help the lower-placed buds bulk up by exposing them to more light. 

Post-Harvest Plan

When you see buds starting to fill out on the plants you’ve grown, you’re likely to feel the irresistible temptation to snip them off and sample them. No harm done if you try a small one or two, but waiting pays big dividends. The buds continue gaining weight and producing more resin as they mature. They reach their peak about 6–8 weeks after the plants start blooming. At about four weeks from when the buds begin appearing, cut off the fertilizer and give the plants water alone—just enough to keep the soil moist but not saturated. This allows time for the plants to absorb and use up the nutrients before you harvest. 

When the leaves begin to yellow and the buds remain the same size for a few days, it’s time to reap what you have sown. But the buds still aren’t yet ideal for consumption: Just-picked, they are too moist to burn. They need a couple weeks to air-dry in a cool, dark place. Hanging the plants upside down or spreading them out on a screen in a garage, attic, or another dry room, allows them to “cure” and prevents mold from forming on the buds while you’re storing them. (If you do this inside, ventilate the room so your home doesn’t smell like a field full of skunk cabbage.) After the curing period, snip off any large leaves still attached to the buds, trim the buds down to roll-able pieces, then store your homegrown stash in airtight containers. The leaves contain small amounts of cannabinoids, so you can consume them, too, if you like. The remaining leaves and stems are an ideal addition to a compost pile, where they break down and become—almost like magic—nutrient-rich soil for your next crop. 

Tip: Check out the color of the pistils (which look like tiny hairs) on the buds. When the pistils have changed from white to red, purple, or gold, the buds are ready to harvest. Thank your plants as you yank them out, and look forward to harvesting more next year, when you’ll employ all you learned this growing season, and apply it to the next. It’s worth the investment. 

5 Success Strategies 

Avoid rookie mistakes by remembering these simple tips. 

  1. See the light. Full sun makes for robust plants. Check at different times of the day to be sure that the spot you’ve selected to plant is not shaded by nearby buildings or trees for extended periods, especially during long summer afternoons. 
  2. Prep the soil. Just any old dirt won’t do for a vigorous cannabis crop. Before planting outside, loosen the soil with a shovel down to 12 inches deep. Mix in an equal amount of compost—homemade or bagged—with the soil you dug up. Give those roots room to grow down below and the plants above will take off, too. 
  3. Water deeply and infrequently. Light daily sprinkling discourages deep, sturdy root growth. Soak the ground around the plants—not the leaves—thoroughly, then wait until it dries up (check by pushing your index finger in up to the second knuckle) before watering well again. 
  4. Watch the boys. One day the plants all look the same, the very next some have tiny dangling sacs of pollen in the crotches of their branches, preparing to immediately shed pollen and spoil your harvest with seedy buds. Check all of your plants daily and banish (kill) those boys immediately. 
  5. Wait, and wait some more. Experienced growers notice that buds double (or more) their weight and amp up their production of THC in the final few weeks of growing. As long as there’s no chance of frost, you can leave the buds on the plant so they bulk up before you harvest. 

Timeline: Seed to Savor

This timing is approximate. Northern latitudes have shorter, more intense growing seasons, so the process is compressed.

  • 4–6 weeks before outdoor temperatures stay above 60ºF overnight
    : Sow seeds inside.
  • 7–10 days later
    : Sprouts emerge.
  • 1 week later: When “true” leaves appear, begin fertilizing weekly, but weakly.
  • 3–4 weeks later: Look daily for male and female reproductive parts and remove males immediately.
  • When temps stay above 60ºF overnight
    : Transplant outside and begin fertilizing twice a week.
  • 3 weeks later
    : Trim top leaves and branches.
  • 2 weeks before nights extend longer than 10 hours
    : Switch to a fertilizer with higher ratios of phosphorus and potassium.
  • 4 weeks later
    : Stop fertilizing. Trim back upper leaves to let more light reach lower buds. 
  • Beat the frost, or else!
    Harvest crop!