Life Cycle of a Marijuana Plant

Quick answer: A marijuana plant is an annual, so it moves from seed to seed within a single season. NC A&T Extension describes four broad stages for hemp, which is the same species: sprouting and emergence, vegetative growth, flowering and seed formation, then senescence, with the whole cycle lasting somewhere between four and six months. Day length drives the switch to flowering. Indoors you control that switch with a light timer, while outdoors the shortening days of late summer make the call. Once you can place a plant in that cycle, you can see what it needs next.

Why Learn the Life Cycle of a Cannabis Plant?

Almost every choice a grower makes ties back to a stage. Light schedules, container size, feeding and the timing of the harvest all depend on what the plant is doing that week. A grower who knows the stages can spot a slow start, an early bloom or a stray male flower before it becomes a bigger problem.

Cannabis is a warm season annual. NC A&T Extension, in its hemp guide titled All About Hemp, calls it an annual herbaceous species and a short day plant that begins to flower as the days shorten. In plain terms, one plant lives one season. It does not build a woody base or come back from the roots next spring. The next generation comes from seed or from cuttings.

The rest of this guide walks through each stage in order, from a dry seed to a finished plant, then covers how indoor and outdoor timing differ, when to harvest and how to carry a favorite plant into the next season.

Before you plant anything, check the rules where you live. State and local laws on home growing vary widely across the United States and change often, so confirm what applies to your address first.

Stage One: Sprouting (24 Hours to Two Weeks)

A cannabis seed holds a tiny resting plant along with a small food supply and a protective coat. Sprouting begins when that resting plant wakes up and starts to grow again.

NC State Extension’s Gardener Handbook, in its chapter on plant propagation, lists the conditions every seed needs. Water comes first. The seed must absorb moisture and then keep a steady supply, because a dry spell after sprouting starts can end the process for good. Seeds also need some oxygen, so the material around them should stay loose and airy rather than soggy. Temperature affects both how many seeds sprout and how fast they do it.

Male, Female and Feminized Seed

Cannabis normally grows as separate plants of each sex. Oregon State Extension, in its publication Hemp sex ed, says young males and females look alike until flowers form. It notes that seed from open pollinated fields usually gives about 30 to 50 percent male plants.

Most home growers want female plants, because the females form the dense flower clusters that are harvested. Males release pollen, and pollinated females put their energy into seed instead.

Feminized seed exists to tilt those odds. Oregon State says feminized seed comes from crossing with pollen made on a genetically female plant, and that the goal is a crop of all female flowering plants. It is careful to describe the result as mostly female plants. The same publication warns that sexual expression in cannabis responds to stress, and that a genetically female plant can produce male flowers at any point in the season. So feminized seed greatly raises the share of females, yet it cannot rule out an occasional plant with both flower types. Our guide to hermaphrodite cannabis shows what those mixed flowers look like and what to do about them. The range of feminized cannabis seeds on our site lists the varieties grown from this kind of seed.

How to Sprout Seeds With Paper Towels

The paper towel method is the simplest way to watch a seed open before it goes into soil. It follows the basics in the NC State propagation chapter: steady moisture, air and warmth.

1. Dampen several paper towels with clean water and squeeze out the excess so they are moist but not dripping.
2. Lay two towels on a clean plate and spread the seeds apart from one another.
3. Cover the seeds with two more damp towels and turn a second plate upside down over the top to hold in moisture.
4. Keep the plates in a warm room away from drafts and direct sun.
5. Check once or twice a day and add a little water whenever the towels start to dry.
6. Wait for a small white root, the taproot, to push out of the shell. This can take anywhere from a day to about a week.
7. Move each sprouted seed into moist soil with the root pointing down, cover it lightly and handle it only by the shell so the tender root stays intact.

Many growers skip the towels and sow straight into a small pot of moist mix. Either route can work, so long as the mix keeps moisture and air in balance.

Stage Two: The Seedling Stage (Two to Three Weeks)

Once the root anchors, the shoot pushes up and opens a pair of rounded seed leaves. True leaves follow. In the NC A&T guide, the first true leaves carry a single leaflet, the next pair carries three, and the count keeps rising as the plant grows. Those jagged, fanned leaves are the first clear sign you are looking at cannabis.

NC A&T tracks the early weeks of field hemp closely. Emergence, from sowing until the seed leaves appear, takes four to 10 days, with soil moisture setting the pace. The next phase, which it calls implantation, lasts about three weeks. During that time the plant puts more growth into roots than into stems and leaves. By the end of it, field hemp stands one to two feet tall with three pairs of leaves.

Seedlings need bright light right away. NC State’s handbook advises moving garden seedlings into strong light as soon as they sprout, with daytime temperatures of about 65 to 70°F and cooler nights. That guidance covers garden seedlings in general, yet it matches what young cannabis plants respond to. Weak light at this stage leads to thin, stretched stems.

Keep watering light and even. A seedling has a small root system that sits near the surface of the container, and soggy mix starves those roots of air.

Cannabis Life Cycle at a Glance

Stage Three: Vegetative Growth

Once the seedling stage is behind it, the plant picks up speed. NC A&T calls this the active growth phase, running from the end of implantation until flowering starts. Most of the stem, branch and leaf mass forms now, and the root system spreads to support it.

Day length controls how long this phase lasts. NC A&T puts the critical photoperiod for hemp at about 14 hours once the young plant has passed its juvenile phase. Give a plant longer days than that and it keeps building leaves and branches. Shorten the days below that line and it starts to flower.

Indoor growers use that rule on purpose. Researchers at NC State grew floral hemp in a greenhouse under 16 hours of light, then cut it to 12 hours to start flowering. UF/IFAS Extension, in its report on supplemental lighting for hemp in Florida, describes trial plots lit from 6 p.m. to midnight for roughly the first two or three months after the plants went into the ground. In that trial, unlit hemp flowered within 20 days of transplanting in fall and 27 days in spring, while lit plots held off for up to 67 and 91 days. Many home growers run 18 hours of light in this stage for that reason. Our walkthrough of veg growth and the move into flowering explains training and the timing of the switch in more depth.

Outdoors, vegetative growth runs from spring planting until the days shorten after the summer solstice. A plant set out early has many long days to grow before it flowers, while one planted in midsummer has far fewer.

Stage Four: The Flowering Stage

Flowering is the stretch most growers have been waiting for. For hemp, NC A&T Extension reports that most cultivars are ready for harvest 55 to 70 days after flowering begins, or about eight to 10 weeks. When nights grow long enough, the plant stops putting most of its energy into leaves and starts forming flowers.

This is when the sexes finally show. Oregon State describes male plants turning slender, with stretched growth at the top and loose clusters of small flowers that hang like ornaments before they open and shed pollen. Female flowers form dense, candle shaped clusters at the tip of each branch, the clusters growers call colas.

If you are growing regular seed, check plants often in early bloom and pull any males before their flowers open. NC A&T reminds growers that fertilized female flowers go on to develop seeds, which is the goal for seed crops but not for growers who want seedless flowers. Keep scouting even with feminized seed. Oregon State points out that stress near harvest can bring on male flower parts in dense female canopies, and it notes that many hemp growers scout weekly, with some crews checking every three to four days as harvest nears.

Comfortable conditions help the plant through this demanding stage. NC A&T lists an optimal growth range of 66 to 77°F for hemp. Steady temperatures, good airflow and an even watering routine all reduce stress during bloom.

Cannabis Life Cycles Indoors and Outdoors

The plant follows the same stages in either setting. What differs is who gets to set the calendar.

Indoors. You decide when flowering begins. Plants can stay in vegetative growth until they reach the size you want, then switch to 12 hours of light. Autoflowering varieties follow a different timing pattern from the photoperiod plants described in this guide, and our page of autoflower seeds describes those types. Plants started from cuttings skip the seed stages entirely. NC A&T points out that floral hemp started from clones has no sprouting or implantation stage, which shortens the cycle.

Outdoors. The sun sets the schedule. Plants grow through the long days of late spring and early summer and begin to flower as days shorten. In North Carolina, most hemp reaches harvest in September or October, NC A&T reports. Location matters too. UF/IFAS notes that day length seldom goes past 14 hours anywhere in Florida, so hemp there tends to flower early under natural light. Growers in Florida may see plants bloom sooner than the same variety grown farther north.

In cold climates, many growers start seeds indoors several weeks before the last spring frost and move the young plants outside once nights warm up. Plants kept in containers can be moved under cover quickly when a cold snap or a storm rolls in.

When Is the Best Time to Harvest Cannabis?

For a long time, growers have judged harvest timing by eye. Growers watch the pistils, the fine hairs on female flowers, darken and curl, and they watch the tiny resin glands change color.

NC State Extension’s visual guide to floral hemp maturation calls that coloring method rather vague. It notes that seed companies and breeders increasingly recommend harvesting a set number of weeks after flowering begins, since that timing is largely set by the plant’s genetics. Its greenhouse photos track two hemp varieties from two to 10 weeks after flowering started, which shows how gradual the change is.

For home growers, the practical approach combines both methods. Note the date you switch the lights or the date you first see flowers, look up the flowering time listed for your variety, and use the pistils and resin glands as a final check. Our page on the final weeks of flowering covers what to watch for as harvest nears.

Trimming and Drying After Harvest

Once the plants are cut, the job shifts from growing to finishing. Trimming removes the large fan leaves and the smaller leaves tucked around each flower. Many growers trim right after cutting while the leaves are still soft, since dry leaves curl inward and are harder to reach.

Resin makes the job sticky, so gloves and a small pair of sharp scissors help. Pick a clean, cool spot to work in and go slowly.

Drying comes next. NC A&T advises drying hemp indoors at 60 to 70°F in moderate humidity for seven to 15 days, with whole plants hung or flowers spread on a rack.

Getting Ready for the Next Growing Season

When the season ends, an annual plant is finished. To grow the same plant again you need new seed or living cuttings taken before harvest.

Cuttings are the most reliable way to carry a favorite plant forward. The propagation chapter from NC State says asexual propagation, which grows a new plant from a piece of stem, root or leaf, produces a plant genetically identical to its parent with few exceptions. Oregon State lists cloning from known female plants as one way growers keep males out of a crop.

Take cuttings from a vigorous plant while it is still in vegetative growth, root them under long days and keep one or two as the start of the next round. Our step by step guide to making cannabis clones walks through the process.

If you would rather start next season from fresh seed, our site groups its varieties into several collections. The 710 seed collection is one of them, and larger gardens can look at bulk seed orders.

Seed options by state: Minnesota, Oregon, South Carolina, Texas and Washington.

Troubleshooting Common Life Cycle Problems

Seeds do not sprout. Old seed, a dry spell or soggy towels are the usual reasons. NC State’s propagation chapter says seeds need steady moisture plus oxygen, so keep towels damp but not dripping.

Seedlings stretch and flop over. The lamp is too dim or hangs too far above them. Move seedlings into brighter light as soon as they sprout.

An indoor plant starts flowering too soon. Check the timer and look for long dark periods. Days shorter than about 14 hours can trigger flowering once the juvenile phase has passed.

Outdoor plants bloom before they size up. They were likely planted late, or the region has short summer days. Get them in the ground earlier next season.

A feminized plant shows male flowers. Stress is a common trigger. Remove the plant or the male flower parts quickly and look for causes such as light leaks, heat or irregular watering.

Sources

• NC A&T Cooperative Extension, All About Hemp: https://www.ncat.edu/caes/cooperative-extension/files/all-about-hemp.pdf
• Oregon State University Extension, Hemp sex ed: a primer on pollination (EM 9279): https://extension.oregonstate.edu/catalog/em-9279-hemp-sex-ed
• NC State Extension, Extension Gardener Handbook, Chapter 13 Propagation: https://content.ces.ncsu.edu/extension-gardener-handbook/13-propagation
• NC State Extension, Visual Guide to Floral Hemp Maturation: https://hemp.ces.ncsu.edu/visual-guide-to-floral-hemp-maturation/
• University of Florida IFAS Extension, Using Supplemental Lighting to Grow Hemp in Florida (HS1452): https://ask.ifas.ufl.edu/publication/HS1452