Cannabis Cultivation

Preventing Flowering in Marijuana Plants

preventing flowering in marijuana plants. This image showcases a healthy indoor marijuana grow setup with vibrant plants under full-spectrum LED grow lights.

Growing marijuana plants can be quite an adventure, but sometimes you might want to delay or prevent flowering to ensure your plants grow big and strong. In this article, we’ll cover the essentials of preventing flowering in marijuana plants, discuss the best techniques, and answer common questions. So, let’s dive in and learn how to keep your plants in the vegetative state for as long as you need.

Understanding the Basics

 infographic-style image illustrating the cannabis lifecycle and the concept of preventing flowering

Before we dive into the how-tos, it’s important to understand why and how marijuana plants flower. Flowering is a natural part of the cannabis lifecycle, triggered by changes in light exposure. When the days get shorter and the nights longer, the plant’s internal clock signals that it’s time to start flowering and produce buds.

Why Prevent Flowering?

There are several reasons you might want to prevent or delay flowering in your marijuana plants:

  • Maximize Growth: Keeping plants in the vegetative state longer allows them to grow larger and stronger.
  • Timing: If you’ve planted too early or need to align your grow schedule with a specific timeline, preventing flowering can help.
  • Issues with Early Flowering: Sometimes plants start flowering too early, which can be problematic. This is sometimes the case with Autoflowering Cannabis Plants.

Light Schedules and Flowering

image illustrating the ideal light schedule for vegetative growth in marijuana plants.  It visually represents the concept of photoperiodic plants and the importance of maintaining an 18-hour light and 6-hour darkness schedule to mimic long summer days.

Light is the most crucial factor in controlling the flowering of marijuana plants. Cannabis plants are photoperiodic, meaning their flowering cycle is controlled by the light they receive.

Ideal Light Schedule

For vegetative growth, marijuana plants need more light. The standard light schedule is 18 hours of light and 6 hours of darkness. This mimics the long days of summer and signals to the plant that it’s time to grow, not flower.

Techniques to Prevent Flowering

Let’s get into the nitty-gritty of how to keep your plants from flowering.

Adjusting Light Schedules

 image illustrating techniques to prevent flowering in marijuana plants. It visually represents adjusting light schedules, showing a marijuana plant under grow lights with a timer set to 16 to 18 hours of light per day, and highlights the importance of uninterrupted periods of darkness.

One of the simplest ways to prevent flowering is to adjust your light schedule. Keeping your plants under grow lights for 16 to 18 hours a day will signal them to stay in the vegetative state. Make sure they get uninterrupted periods of darkness, as light leaks can trigger flowering.

Temperature Control

image illustrating temperature control for preventing flowering in marijuana plants. It visually represents a controlled grow room with temperature settings, showing the importance of maintaining stable temperatures and avoiding sudden drops or prolonged exposure to cold.

Maintaining the right temperature is also key. Keeping your grow room between 70-85°F (20-30°C) during the day and slightly cooler at night can help. Sudden temperature drops or prolonged exposure to cold can stress plants and induce flowering.

Use of Supplementary Lighting

image illustrating the use of supplementary lighting for outdoor marijuana plants. It visually represents how supplementary grow lights can extend the daylight period to ensure plants receive the required light, even as days get shorter.

If you’re growing outdoors and the days are getting shorter, you can use supplementary lighting to extend the daylight period. Simple outdoor grow lights can be set up to ensure your plants get the required light.

Pruning and Training

image illustrating pruning and training techniques for marijuana plants to delay flowering. It visually represents how pruning and topping encourage bushier growth and delay the flowering process.

Pruning and training your plants can also help delay flowering. Techniques like topping, where you cut off the top growth, can encourage bushier growth and delay flowering.

Common Questions and Answers

Here are some frequently asked questions about preventing flowering in marijuana plants.

Is growing seeds under grow lights 16 hrs on 8 hrs off enough light to stop flowering?

image illustrating a marijuana plant under grow lights with a timer showing a 16-hour light and 8-hour dark schedule. It visually represents the importance of maintaining this light schedule to prevent flowering and keep the plants in a vegetative state, emphasizing the need for uninterrupted darkness.

Yes, a light schedule of 16 hours on and 8 hours off can help prevent flowering. It’s enough light to keep the plants in a vegetative state, but ensure there are no interruptions during the dark period.

Will reducing the temperature to 16-18 degrees Celsius and using a low-effect 6500 K 20W tubelight keep them alive?

Lowering the temperature to 16-18 degrees Celsius can help slow down the plant’s metabolism, but it’s essential to provide enough light and warmth to keep the plants healthy. A 6500 K 20W tubelight might not be sufficient; consider stronger grow lights for better results.

Should I use a 20 W heat mat under the soil to boost microbiological life?

image illustrating the use of a 20W heat mat under the soil for marijuana plants. It visually represents how the heat mat maintains soil temperature, promotes healthy root development, and increases microbial activity, especially in colder environments.

Using a heat mat can help maintain soil temperature, promoting healthy root development and microbial activity. It’s especially useful in colder environments.

How should I manage watering during this period?

During the vegetative stage, maintain a consistent watering schedule. Ensure the soil stays moist but not waterlogged. Overwatering can lead to root rot and other issues.

What if the plant has started to bud and it’s still 2’ tall?

 image illustrating how to revert a marijuana plant to the vegetative state if it has started to bud prematurely. It visually represents increasing the light hours to 18 hours on and 6 hours off, or even setting the lighting to 24 hours a day, along with removing buds to encourage vegetative growth.

If your plant has started to bud prematurely, you can try to revert it to the vegetative state by increasing the light hours back to 18 hours on and 6 hours off. This process can take some time, and you may need to remove any buds to encourage vegetative growth. If this doesn’t work they you can even try setting your lighting to 24 hours a day to get it to go back to it vegatative growing state.

Tips for Successful Vegetative Growth

Here are some additional tips to ensure your plants stay in the vegetative stage and grow healthy:

 image illustrating tips for successful vegetative growth in marijuana plants. It visually represents nutrient management with high nitrogen fertilizers and avoiding high phosphorus fertilizers, as well as regular monitoring for signs of stress, pests, or diseases.

Nutrient Management

Provide your plants with the right nutrients. During the vegetative stage, focus on high nitrogen fertilizers. Avoid high phosphorus fertilizers, as they promote flowering.

Regular Monitoring

Keep an eye on your plants daily. Look for any signs of stress, pests, or diseases. Early detection and treatment are key to maintaining healthy growth.

Pros and Cons of Preventing Flowering


  • Larger Plants: Delaying flowering allows plants to grow bigger and stronger.
  • Controlled Timing: Align your grow cycle with your needs.
  • Better Yield: More vegetative growth can lead to higher yields.


  • Energy Costs: Extended light periods increase energy consumption.
  • Potential Stress: Constant changes in light schedules and temperatures can stress plants if not managed properly.

Specifications for Grow Lights and Equipment

image illustrating the specifications for grow lights and equipment needed for marijuana plants. It includes visual representations of various grow lights, a 20W heat mat, a digital thermometer with hygrometer, and a programmable light timer, each clearly depicted to indicate their purpose.

Here’s a quick guide on the specifications of grow lights and equipment you might need:

Grow Lights6500 K, 200W LEDEnsures sufficient light for growth
Heat Mat20WMaintains soil temperature
ThermometerDigital with HygrometerMonitors temperature and humidity
Light TimerProgrammableAutomates light schedule

Frequently Asked Questions (FAQ)

How long does it take to revert a plant to the vegetative state?

Reverting a plant to the vegetative state can take a few weeks. Patience and consistent light schedules are key.

What kind of light is best for preventing flowering?

Full-spectrum LED lights with a color temperature of 6500 K are ideal for vegetative growth.

Can pruning help prevent flowering?

Yes, pruning can delay flowering by encouraging bushier growth and more vegetative activity.

Is it too late to start using a night light to prevent flowering?

It’s never too late to try using supplementary lighting. However, the earlier you start, the better the results.

What should I do if my plants start flowering too early?

Increase the light hours to 18 hours on and 6 hours off, remove any buds, and monitor for stress.


Preventing flowering in marijuana plants requires a bit of know-how and patience, but with the right techniques, you can keep your plants in the vegetative state and ensure they grow big and strong. Remember to maintain proper light schedules, control temperatures, and provide the necessary nutrients and care. Happy growing!

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