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From Seed to Harvest: The Life Cycle of Cannabis

By Monica Mansfield | Last updated: June 1, 2021
Key Takeaways

Knowing how to care for your cannabis plants at each of the four distinctive stages of their life cycle will provide a solid baseline of knowledge and healthy, productive gardens.

Caption: Cotton Candy Grapes Source: Kyle LeGrow for High Voltage Extracts

It can take four to eight months to grow a cannabis plant. During this time, it goes through four distinct stages: germination, seedling, vegetative, and flowering. It is essential for cannabis growers to understand each stage in the life cycle so they can properly care for their plants. Each phase requires different nutrients, hours of light, and type of light. There are also different tasks that can help make each stage more successful.

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Germinating cannabis seeds.Germinating cannabis seeds.

Germination Stage

It all begins with a seed. If stored in cool, dark conditions, a cannabis seed can remain viable for years. The best seeds are hard and dry and will be light to dark brown in color. Underdeveloped seeds tend to be soft and either white or green. It’s very unlikely these seeds will germinate.

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The seed lies dormant until it is exposed to warmth and moisture. You can germinate your seeds by planting them in a moistened seedling starter mix, covered with plastic and placed on a heat mat. It is important to use a seed-starting mix instead of potting soil.

There is enough nutrition in a seed to feed a sprout for about two to three weeks. Any additional fertilizer can burn your plants at this tender age. Once planted, a seed can take five to 10 days to sprout.

Once your seeds have sprouted, the two seedling leaves will be the first to appear. Place a fluorescent grow light about two inches from the top of your plants for 18 hours per day. You don’t need a powerful light for them in the beginning. When the true leaves appear, your little plants can officially be considered a seedling.

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Cannabis plant in its seedling stage.Cannabis plant in its seedling stage.

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Seedling Stage

The seedling stage of cannabis plant lasts three to six weeks, depending on environmental factors and the strain you’re growing.

During this time, your seedlings are focusing their energy on growing roots and foliage. Because the roots are so small, be careful not to overfeed or overwater. Use a fertilizer high in nitrogen and be sure to dilute it so you don’t harm your plants.

Fluorescent lights still work well at this point. Set your timer so the lights are on for 18 hours and off for six.

Seedlings are susceptible to pests and disease at this age, so this is a good time to apply a preventative neem oil treatment. It’s much easier to prevent spider mites and powdery mildew than to treat them while your plants are so young. If they do get infested or infected at this age, the stress on your plants will likely produce a smaller harvest down the line.


Cannabis in the vegetative stage.Cannabis in the vegetative stage.

Vegetative Stage

After a few weeks as seedlings, your cannabis plants will outgrow their starter pots and start demanding more food and light. The roots and foliage grow rapidly during this stage, which allows the plant to take in more nutrients and carbon dioxide. Don’t be surprised if your plant shoots up two inches in one day!

If you don’t already know, this is when you’ll be able to identify whether you are growing an indica or sativa. Indicas tend to be short and bushy, while sativas are lanky with less foliage.

You will also be able to identify the sex of your plants. About four weeks into the veg cycle, pre-flowers start to appear. By six weeks in, you should be able to determine whether those new buds are male or female. Most growers remove the males from their garden, so they don’t pollinate the females and cause seeds to form.

(Read also: Anatomy of a Cannabis Plant)

When growing indoors, the vegetative stage can last one to four months, or even indefinitely in the case of mother plants. You control the length of this phase by the number of hours of light you give your plants. As long as they receive 18 hours, they will remain in this stage.

During the vegetative stage, you’ll need to trade in your fluorescent lights for a metal halide or powerful LED. This blue light mimics the light in spring and sends the message to grow roots and foliage to prepare for the flowers.

If you haven’t already, transplant your cannabis into larger pots and start feeding them more. As they grow, be mindful you will need to increase the PPM of your nutrient solution and transplant them into larger pots as needed.

At this age, your plants need high levels of nitrogen and modest amounts of phosphorus and potassium. Silicon is also beneficial at this stage because it helps to build strength in the stalk and stems, which you’ll need to support those big buds that will soon grow.

As your plants grow taller and fill out, you’ll need to start pruning and training them. This focuses their energy on growing large colas, opens up the plant so light can reach all the leaves, and prevents fungal diseases by increasing air flow.

The general rule of thumb is to flip the lights to 12/12 and trigger the bloom cycle when your plants are about one third of the size you want them to be at harvest.


Flowering cannabis plant.Flowering cannabis plant.

Flowering Stage

You imitate autumn in your garden when you reduce the light to 12 hours on and 12 hours off, and switch to a red high-pressure sodium bulb. This triggers your cannabis plants to start blooming so they can procreate before they die at the end of the season.

The flowering stage lasts six to 10 weeks, depending on the strain you’re growing. During this time, dense buds covered in a sweet-smelling, sticky resin will form on your plants. This resin is where the THC and terpenes are, and so growers do whatever they can to grow the stickiest colas possible.

Your fertilizing schedule will change during this stage. Start feeding your plants minimal amounts of nitrogen, moderate amounts of potassium, and high amounts of phosphorus. This is the time to add bloom boosters and sugars to your regimen.

Be on the lookout for nutrient deficiencies or toxicities during this phase. Brown leaf tips can signal nutrient burn, while yellowing leaves may indicate a nutrient deficiency. It is normal, however, for the lower leaves to turn yellow towards the end of the flowering cycle, when your plants feed on themselves for more efficient nutrition.

(Read also: 5 Flowering Stage Tips for Cannabis)

Keep feeding your plants until about 10 days before harvest, and then stop fertilizing and flush your crop. This clears your plants of excess nutrients and is crucial to making sure your end product is smooth instead of harsh.

As your buds grow large and dense, environmental conditions and poor air flow can cause bud rot. If you don’t catch it in time, you can lose all of your plants. Keep a close eye on your buds as harvest time approaches. Inspect your buds often and harvest immediately if you see signs of rot. If you catch it early, you can cut the rot out of your buds and salvage most of your crop. You’ll know your cannabis is ready to harvest when the pistils, or the hairs, turn the color of rust and the resin changes from clear to a milky white.

If you understand the life cycle of cannabis, you’ll be able to care for your plants the right way in each stage of their life and anticipate problems before they occur. You’ll be a better grower and have top shelf smoke to prove it.

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Written by Monica Mansfield | Homesteader, Owner & Writer of The Nature Life Project

Profile Picture of Monica Mansfield

Monica Mansfield is passionate about gardening, sustainable living, and holistic health. After owning an indoor garden store for 5 1/2 years, Monica sold the business and started a 6.5-acre homestead with her husband, Owen. She writes about gardening and health, as well as her homestead adventures on her blog at thenaturelifeproject.com.

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