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Find Out Why Your Cannabis Is Not Flowering

Cannabis not flowering

Your first time growing cannabis is exciting and fun and something we strongly suggest all marijuana enthusiasts try at least once. However, it can also be a time of anxiety and stress. While they don’t always happen, many potential issues can keep you up at night. Your cannabis not flowering is one of the most common concerns for first-timers.

If you’re worried about your cannabis not flowering or you want to learn how to make a weed plant bud, stick around. Keep reading, and you’ll learn about the stages of growth in marijuana and how to start flowering cannabis.

With a solid knowledge of the growth cycle of your plants, you won’t need to worry about your cannabis not flowering. You’ll find out how and why marijuana flowers below, along with how to identify issues and prevent potential problems from occurring.

Knowing is half the battle when cultivating productive crops of cannabis, so let’s jump in and start learning.

Marijuana plant in veg stage
Marijuana plant in veg stage

Vegetative vs. flowering stage

Cannabis cultivation begins with germinating your seeds. Once germinated, marijuana seeds move through three distinct growth phases; seedling, vegetative growth, and flowering. Let’s take a look at each stage of growth.


Cannabis seeds send out a delicate stem topped with two tiny round leaves called cotyledons. This first pair of leaves absorb light to provide the seedling with energy to produce its first ‘true’ leaves.

Your first pair of distinctly shaped leaves emerge within a week. Once the plant is established and has 6–7 pairs of leaves, the cotyledons wilt and die. This point marks the end of the seedling phase and the transition to true vegetative growth.


The vegetative stage sees your plants rapidly grow in size. As the days and weeks progress, more and more sets of fan leaves develop from the quickly thickening central stem. With each set of leaves, the space between the nodes on the central stem increases.

Under natural conditions, cannabis plants remain in the vegetative phase until the arrival of Fall. Shorter days signal winter’s arrival to the plants, which kickstarts their flowering period. Indoor growers control the photoperiod of their crop, remaining in the vegetative stage as long as they receive enough light. This control means indoor growers can initiate or delay the switch to flowering as desired.

Various other factors affect the length of vegetative growth. Pure sativa or sativa-dominant strains usually take longer than their indica counterparts. Temperature, humidity, and photoperiod length also affect the length of the vegetative phase. Cannabis not flowering during this time is normal.

Marijuana cultivated commercially usually spends 60 days in vegetative growth. For home growers, you need to consider the space available. A common mistake made by new gardeners is to assume the plants stop growing once flowering begins. Switching too late results in a cramped grow room or tent and other potential problems like light-burn or foxtailing buds.

Most cannabis strains experience a huge ‘stretch’ in the early weeks of flowering. Account for this when growing in a vertically-limited space. Plants can double or triple in size, so planning ahead is crucial. To give yourself an idea of when to switch from veg to flower, measure the distance from your light in its highest position to the base of the plants.

For example, let’s say you have a vertical space of 100 inches. You’ll want your lights 12 inches above your plants at all times. Subtract twelve from the total height of 100in for 88in. Take this maximum height and divide by three for 29.3 inches (2.4 feet). When your plants reach this height, switch to flowering, knowing you have the space to accommodate the stretchiest of stretches.


Flowering is, as they say, where the magic happens. You can break down this stage of growth into further sub-stages. Knowing these phases helps you better identify how far along your plants are and ease your worries over cannabis not flowering.

The first few weeks of the flowering stage are when the marijuana plants begin exhibiting sex. If you’re using regular cannabis seeds, this is when you’ll need to identify and remove any male plants from your crop quickly. This pre-flowering phase sees continued plant growth and the formation of female pistils or male pollen sacs.

Once sexed, female crops proceed through their early flowering phase. Small buds appear at the nodes of the plants. Growth begins to slow over the next 2–3 weeks as they enter peak flowering. Check our report on the first signs of the flowering stage for detailed info.

Once the plants enter peak flowering mode, their focus will switch entirely to bud production. The huge, dense nugs and colas you’ve been waiting for begin to swell in size and increase in weight.

The final stage of flowering occurs when the buds are all fully formed, and the maturation process begins. As harvest approaches, the white pistils become less spiny, curling up and turning a yellow or orange color. When about half the pistils are a deep orange, it’s time to reap the rewards.

Early flower stage
Early flower stage

When do cannabis plants start to flower?

So, how to make marijuana plants bud? In most cases, cannabis plants start to flower when they experience a daily, uninterrupted 12-hour period of complete darkness. However, there’s an exception to be addressed; autoflower seeds.

Auto cannabis seeds aren’t reliant on photoperiod to begin flowering. Autoflowering variants start blooming regardless of the light schedule once they’ve sufficiently established themselves with a few weeks of vegetative growth.

If you’re growing autoflower seeds, there’s no need to worry over how to start flowering cannabis. Give these plants enough food, keep them well lit, and they’ll take care of the rest, flowering once they’re ready.

For those using regular, non-auto strains, providing the correct amount of darkness is the sole decider in how to make marijuana plants bud. Remember, flowering won’t happen overnight, so be patient, and don’t panic if your cannabis plants are not flowering immediately.

Why your cannabis is not flowering: 5 reasons and what to do

If your cannabis plants are not flowering, there are a few reasons why this might be happening. 

Let’s take a look.

Plants need more time

Cannabis not flowering may mean that your plants simply need more time. The pre-flowering stage can take several weeks before signs of buds appear. Maintain a consistent nutrition and lighting schedule and remain calm. Don’t be tempted to change around the photoperiod once you’ve switched to a 12/12 schedule if you have a weed plant not flowering.

Light leaks

Indoor growers must ensure that absolutely no light enters their grow room or tent during the plants’ ‘nighttime.’ Even a small sliver of light is enough to confuse the plants and lead to cannabis not flowering.

Ideally, you’ll have checked for light leaks before starting by going into your grow area during the ‘nighttime’ and checking for light. Seal up any cracks or holes you find so that it’s pitch black when the lights are off.

Cannabis in the vegetative stage under LED lights
Cannabis in the vegetative stage under LED lights

Incorrect photoperiod

Consistency is key when flowering marijuana plants. While it might not seem a big deal, missing the window for turning on or off your grow lights by even a half-hour throws off the plants. This may also lead to the cannabis not flowering.

A continued lack of consistency in lighting may also result in hermaphroditism which is best avoided at all costs. Invest in a high-quality timer setup to control your photoperiods. Avoid interrupting the plants at night. If you absolutely must do something during the plant’s dark period, use only a green light.

Lighting malfunction

Cheap, low-quality mechanical timers have a nasty habit of malfunctioning, running slowly, or breaking entirely, causing problems for your plants. A timer failing to work properly may result in plants returning to vegetative growth or displaying hermaphroditic tendencies.

Incorrect seeds

This last one is highly unlikely and applies to autoflower vs. photoperiod cannabis seeds. Let’s say a friend threw you what they thought were some auto seeds, when in fact, they’re photoperiod. This could result in the cannabis not flowering as you won’t have been growing it like a photoperiod.

How to make marijuana plants bud?

When it comes to how to make a weed plant bud, there’s no magic tricks or secret tips. All you need to do is mimic the natural conditions outdoor plants experience.

This means planting at the right time of the year for outdoor growers. Outdoor crops need enough time to grow but have to finish before the winter comes. For most strains grown in the Northern Hemisphere, harvest time comes around September–October.

For indoor cultivators, you need to provide your plants with 12 hours of pure darkness every day. Ensure there aren’t any light leaks in your grow room or tent, and maintain a strict, consistent lighting schedule for the best results.

Those raising autoflowers can kick back and relax. Your miniature marijuana plants begin flowering after a few weeks of vegetative growth. Photoperiod management isn’t required, and cannabis not flowering is rarely an issue.

Cannabis flowering
Cannabis flowering

Don’t worry, grow cannabis

Hopefully, your worries over cannabis not flowering and any questions of how to make marijuana plants bud have been answered above.

There’s, unfortunately, no shortcut to cultivating enormous crops of cannabis, but at the same time, all it requires is time, patience, and some TLC. By removing some mystery around how the plants work, you’ll have an easier time growing regular or feminized cannabis seeds.

If you’re not sure you can provide the consistency required for photoperiod strains, autoflower cultivars are always an option. Auto crops grow shorter and produce smaller yields than their photoperiod counterparts, but eliminate light management and concerns over cannabis not flowering. Check out our selection of autoflower seeds, pick up a pack, and get growing.

Whatever you decide, be sure to check out our Grow Your Own with Kyle Kushman blog series. Hit the link for a wealth of helpful tips and growing insights from one of the masters of growing.

About the author: Parker Curtis

Parker Curtis has around a decade of cannabis-growing experience, specialising in soil-less and hydro grows. He’s mastering outdoor, greenhouse, and indoor grows.

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