How Long Does It Take To Grow Weed?

Sophia Delphi July 01, 2022 - 8 min read
Fact Checked

It’s frustrating to watch and wait as plants grow.

You could be growing tomatoes, or berries, or cannabis. It doesn’t matter. When you start the process, you don’t picture the seedlings pushing up through the soil and spreading, their stems and leaves developing, their buds appearing and opening, or the flowers eventually blossoming.

You picture the crop they’ll eventually produce. And the waiting can make you crazy.

It’s particularly difficult when you’re growing cannabis. After all, you can pick up tomatoes or strawberries anywhere. But weed is…well, weed. It’s special. You’ve cared for it more diligently than the vegetables or fruit you may have growing in your backyard garden.

And damn, the process seems to take forever.

Just how long does it take to grow weed? Let’s find out.

Types Of Marijuana Plants And How Long They Take To Grow

Not all cannabis plants have the same growing cycle. Some may be ready for harvest in just two or three months, while many more will require 4-6 months of growth before their precious crop can be enjoyed.

There are several factors that determine how it takes for a weed plant to reach maturity.

Sativa vs. Indica

Generally speaking, indica plants grow faster than sativas. That’s partly because indica plants grow much shorter, spreading out to become bushy instead of tall. It’s also because indicas’ flowering stage (the final stage of growth, when buds appear, grow, and mature) is much shorter than it is for sativa plants. Many strains of indica or indica-dominant cannabis produce their crops in just 8-12 weeks.

Indicas grow fast because they originally developed in harsher, colder climates, where weather conditions only allowed for a short growing season. Sativas, on the other hand, first grew in equatorial climates where there was little pressure on them to grow quickly. Since they could “take their time,” they grew quite tall and took a long time to flower; they have retained those characteristics over the centuries. That’s why sativas may grow for as long as five or six months before they’re ready to harvest.

Autoflowering vs. Photoperiod Plants

Most cannabis plants are what botanists call “photoperiod” plants. That means their growth is heavily dependent on the amount of light they receive.

In simple terms, photoperiod plants have evolved to take advantage of the natural sunlight that’s available. They’re generally in their vegetative stage (when the plants grow substantially in size and their foliage develops) when daylight is at its peak, during the late spring and earlier summer months. But late in summer and in early fall, when the plants start to receive less sun each day, they advance to the final, flowering stage.

As you can guess, that extends the length of their growing cycle considerably. Standard weed plants grow from spring until fall, which is why they may not finish producing their crop until four, five, or six months after planting.

Fairly recently, growers decided to find a way to shorten the cannabis growing season so they could plant and harvest more than one crop per year. They crossbred some marijuana strains with the cannabis subspecies ruderalis, and came up with “autoflowering” plants.

Why ruderalis? That plant’s growth cycle doesn’t depend on the amount of light it receives. So autoflowering weed plants, just like ruderalis plants, don’t wait to flower until late summer. They only need a few weeks in the vegetative stage (compared to several months for photoperiod plants) and then automatically switch to the flowering stage – no matter what the light conditions are.

In short, autoflowering strains only need ten weeks (or even less) to produce their crops. They’re ideal for those who can’t wait – or don’t want to wait – for the typical cannabis growing cycle to run its course.

We should also mention that even though smaller plants mean smaller harvests, the weed produced by today’s autoflowering strains is usually bred to be extremely potent.

Weed Strains

We’ve already covered the most important fact to know about cannabis strains and growing time: autoflowering plants are ready to harvest much faster than most photoperiod ones. However, there are some “standard” weed plants that grow more quickly than you’d expect.

Photoperiod strains like Early Girl, OG Kush, and Critical Kush usually flower within about 8-10 weeks of planting. That’s not as fast as autoflowering strains that flower in 3-4 weeks, but it’s still earlier than the average strain of marijuana. You’ll have to spend a lot more time caring for “early” photoperiod strains than you would an autoflowering strain, but they expand the range of choices you have for plants that don’t take an entire season to grow.

Growing Methods And The Growth Cycle

Image of Hand Holding Alarm Clock and Weed Plants in the Background

Your choice of techniques will affect how long it takes to grow weed, too. For example, you can shorten the grow time by 30-50% by using a hydroponic system instead of planting in soil. You can cut the process short by starting with clones instead of seeds.

And giving plants the right type of nutrition during each stage of their growth will encourage optimal development and lead to an earlier harvest. Just throwing a little fertilizer at your plants from time to time? Expect them to take longer to grow.

The most essential factor is whether you grow your plants indoors or outdoors. An outdoor grow means the crop’s development will depend on long the sun shines each day, and how long summer lasts in your area. An indoor grow, though, gives you full control over the amount of light your plants will receive – and that allows you to “force” them to grow faster and flower earlier.

Giving weed plants 24 hours of light per day will accelerate the vegetative stage and move them through that stage faster. (Be aware, though, that many growers say keeping the lights on continuously makes plants more likely to contract diseases. They limit light exposure to 18 hours a day during the vegetative stage.) But as long as weed plants receive 14 hours of light each day, they’ll stay in the vegetative stage virtually indefinitely.

The real trick to fast growth is forcing the plants into the flowering stage, which you do by limiting the amount of light they get during the vegetative stage. Once weed plants receive 12 straight hours of darkness every night, they “believe” that the season’s end is nearing, and will begin flowering almost immediately.

Tricking the plants with light can be done at just about any time in their growth cycle. However, the less time you give them to grow and mature, the smaller your crop will be.

So How Long Does It Really Take To Grow Weed?

There’s no definitive answer to the question. It can take anywhere from 2-6 months, depending on the type of strain you choose to grow, how you grow it, and how patient you are.

The real advantage to growing an autoflowering strain or pushing your photoperiod plants to flower as soon as possible? You’ll have time to grow a second crop before winter arrives.

How Long Does It Take To Grow Weed? FAQ

Q: When should you start your cannabis seeds in order to get the plants to grow faster?
A: If you’re going to grow outdoors, you won’t be able to do too much to encourage faster growth, other than using autoflowering strains. Since it’s usually too cold outdoors until mid-to-late spring (depending on where you live), it’s best to start them indoors at least a month earlier than that. If you’re growing indoors and want to encourage rapid growth, the time of year shouldn’t matter all that much. Firm control of the lighting conditions in your grow room will give you the ability to determine when the plants will flower and be ready for harvest.

Q: Are the most popular strains available as autoflowering seeds?
A: Sorry, it doesn’t work that way. Autoflowering strains are specially bred, and you’ll have to choose one of those strains. The good news: there are more and more of them – with different characteristics and THC levels – available every year.

Q: Do you have to wait until the flowering stage is over before harvesting? Or can you collect your flower sooner than that?
A: You can harvest the buds whenever you like, but they aren’t fully developed and at their peak until the end of the flowering stage. You’re better off trying to “save time” toward the end of the vegetative stage, by forcing the plants to flower.