Switching from Veg to Flower With Cannabis: Everything You Need to Know

Timing is everything, and growing cannabis is no different. Knowing when to flip your precious plants from their vegetative stage to their flowering stage can significantly impact your yield come harvest time. 

For most cannabis strains, the standard 12 hours of light and 12 hours of uninterrupted darkness (12L/12D) photoperiod works well for switching from vegetative to flowering stages. 

However, studies have shown that if you're growing a high-CBD strain like Cannatonic, you might want to try starting with 14 hours of light and 10 hours of darkness (14L/10D). This has been shown to boost CBD production by 50-100%.

Nailing this transition is crucial, and we’re here to share everything we’ve learned to help you achieve massive buds.

In this guide, we'll cover the exact steps to transition your plants seamlessly, advanced tips to boost your yield, and personal insights that highlight what works (and what doesn’t). 

Let’s get to it!

Understanding Cannabis Growth Stages

The journey from seed to harvest is filled with distinct stages that each play a crucial role in the development of your cannabis plants.

Let’s break down these stages in detail.

Germination Stage (3-10 days)

This is where it all begins. Your seeds sprout, and tiny roots start to develop. Kyle Kushman has already written a full guide on how to germinate seeds for optimal success, so check it out on our site here! 

Seedling Stage (2-3 weeks)

Your plants develop their first true leaves and begin to establish a root system.

You'll notice the first set of true leaves—those iconic serrated cannabis leaves—unfurl. This stage is crucial because your plant is very delicate and vulnerable to environmental stresses. 

Ensure your seedlings get plenty of light (18-24 hours of light per day), a gentle breeze to strengthen their stems, and a consistent supply of water and nutrients. Avoid overwatering, as this can lead to damping off, a common fungal problem that can kill young plants.

Vegetative Stage (3-16 weeks)

Your plants focus on growing leaves, stems, and roots. This is where you can shape and train them.

This is the phase where your cannabis plants develop most of their foliage. The more leaves they grow, the more energy they can produce through photosynthesis. 

This stage can last anywhere from a few weeks to several months, depending on your goals and space. 

You'll want to provide 18-24 hours of light per day, plenty of nutrients (especially nitrogen), and ample water. Don’t maintain this light cycle for extended periods as your plant still needs rest periods. 

This is also the best time to train your plants using techniques like topping, low-stress training (LST), and pruning to shape them and maximize light exposure to all parts of the plant.

Flowering Stage (8-10 weeks)

The magic happens here—buds start to form, and your plants show their true potential.

Now you can switch your light cycle to 14 hours of light and 10 hours of uninterrupted darkness (for a Cannatonic strain) or 12 hours of light and 12 hours of darkness (12L/12D) for regular plants. Your plants receive the signal that it’s time to flower. 

Over the next several weeks, you'll see bud sites form and swell, producing resin-rich flowers. During this stage, you should switch to a nutrient mix lowering in nitrogen and higher in phosphorus and potassium, specifically meant for flowering plants. 

Keep a close eye on your plants for signs of pests or nutrient deficiencies, as any issues can impact your final yield.

The Science Behind the Switch From Veg to Flower

Cannabis plants are photoperiodic, which means they flower based on light cycles. Outdoors, happens naturally with the changing seasons. Indoors, you control this by switching your light schedule from 18 hours of light (veg) to 12 hours (flower).

Why does this matter? Because timing is everything. By mimicking the natural reduction of daylight hours, you signal to your plants that it's time to reproduce before the end of their lifecycle. 

This process triggers hormonal changes within the plant, leading to the development of flowers. Understanding this natural rhythm helps you create optimal growing conditions indoors, ensuring your plants transition smoothly and produce abundant, high-quality buds.

Factors to Consider Before Flipping From Veg to Flower

When to switch your cannabis plants from vegetative to flowering is an important decision that can have a big impact on your final production. Here are some important considerations to consider.

• Plant Height and Space

Measure your plants. They can double or triple in height during flowering so make sure you have enough vertical space.

Before flipping, consider how much vertical space you have in your grow area. Most cannabis plants will double or even triple in height during the flowering stage, a phenomenon known as “the stretch.” 

If you’re growing in a tent or indoor grow room, make sure you have enough space for your plants to grow upwards without hitting the lights. 

It all depends on several factors like the strain, light intensity, and difference in temperature between day and night, but the general rule is to flip your plants when they are about a third the height of your grow space.

This is because you’ll need to leave plenty of room to avoid having your plants grow too close to your hot grow lights. 

• Growing Environment

Indoor growers have the advantage of potentially controlling every aspect of the growing environment. Ensure your temperature, humidity, and light conditions are optimal for flowering. 

Temperatures should be slightly lower than during the veg stage (around 68-82°F), and humidity should be reduced to 40-60% to prevent mold and mildew. 

If you’re growing outdoors, you can use light deprivation techniques—covering your plants with a blackout tarp for 12 hours a day—to induce flowering early.

This is especially useful if you want to control the plant’s eventual size or possibly complete multiple harvests within a single season. 

• Plant Health

Ensure your plants are healthy and stress-free before flipping. If you’ve recently transplanted or pruned heavily, give them time to recover.

To make sure you’re transplanting right, here’s a practical guide on how to transplant cannabis plants.

Healthy plants are more likely to thrive during the flowering stage. Before flipping, make sure your plants are in peak condition. 

Look for vibrant green leaves, sturdy stems, and a robust root system, and apply all your preventative measures against pests and mold. 

If you’ve recently transplanted or done some heavy pruning or training, give your plants a couple of weeks to recover. Stressed plants can struggle to transition smoothly, leading to lower yields and potentially more problems with pests and diseases. 

A little patience now can pay off with a bigger, healthier harvest later.

• Growing Techniques and Timing

Different growing techniques can significantly impact when and how you should flip your plants from veg to flower. Let’s explore some of the most popular methods.

• Sea of Green (SOG)

Sea of Green, or SOG, is a technique that maximizes space by growing many small plants. This method is ideal if you have limited vertical space and want quick turnarounds.

How It Works: In SOG, you grow a larger number of smaller plants close together. This technique allows you to flip to flower earlier, typically when the plants are about a foot tall. 

Why so soon? Because these plants will focus their energy on producing one main cola rather than multiple branches, leading to a faster harvest.

Last summer, we experimented with SOG in a cramped indoor space. We packed a dozen small plants into a tiny grow tent and flipped them at just 12 inches tall. 

The result was a forest of compact, dense buds ready for harvest in no time, proving that SOG is perfect for growers looking to maximize yield in a limited space.

• Screen of Green (ScrOG)

ScrOG, or Screen of Green, is all about maximizing light exposure and bud sites by training your plants to grow horizontally through a screen.

How It Works: In ScrOG, you place a screen or net above your plants and weave the branches through it. 

The technique helps distribute light evenly to all parts of the plant, promoting a uniform canopy. You should flip to flower when the canopy fills about 70% of the screen.

We’ve found that ScrOG works wonders for tall sativa strains. Once, we had a sativa-dominant hybrid that was getting out of control.

By using a ScrOG net and weaving the branches through it, we created an even canopy that maximized light exposure and boosted our overall yield. 

• Lollipopping

Lollipopping involves trimming the lower growth of your plants to focus energy on the top buds. This method ensures that the plant’s resources are directed towards the most productive parts.

How It Works: By removing the lower leaves and branches that receive less light, you can help your plant focus its energy on the top, more exposed buds. This technique is particularly effective for sativa strains, which tend to stretch more. 

For indicas, you can afford to flip a bit later since they are generally shorter and bushier.

Step-by-Step Guide to Flipping From Veg to Flower

Here’s a step-by-step guide to ensure a smooth flip.

Step 1: Adjust Your Light Schedule

The first and most crucial step is to switch your light schedule to a 12/12 cycle. This means 12 hours of light followed by 12 hours of uninterrupted darkness. This change signals to your plants that it’s time to start flowering.

Why It Matters: The reduction in light mimics the natural progression from summer to fall, triggering the plant’s flowering hormones. Ensuring complete darkness during the dark period is critical, as even a small amount of light can disrupt the flowering process.

Step 2: Modify the Environment

As your plants transition to flowering, they require different environmental conditions. Lower the humidity to 40-60% to prevent mold and mildew, and maintain temperatures between 68-82°F. If possible, increase CO2 levels, as this can boost bud growth.

Flowering plants are more susceptible to mold and mildew, especially as buds become denser. Controlling humidity and temperature helps create an optimal environment for bud development.

We once neglected to adjust the humidity during a particularly humid summer. The result was a minor mold outbreak that could have been disastrous. Since then, we’ve been diligent about monitoring and adjusting environmental conditions during the flip.

Step 3: Nutrient Management

Switching your nutrient mix is crucial during the flip. When your plants start to flower, switch to a nutrient mix lower in nitrogen and higher in potassium and phosphorus. 

Nitrogen supports vegetative growth, while phosphorus and potassium are critical for flowering. Check out some of our bestselling nutrient mixes here! 

Step 4: Monitor and Protect

Regularly check your plants for pests and diseases. Early detection is key, as problems are easier to manage before your plants are fully into the flowering stage.

Pests and diseases can severely impact yield and quality. Regular monitoring ensures you can address issues promptly, keeping your plants healthy and productive.

Advanced Tips for Maximizing Yield

If you want to take your switch to the next level, here are a few more advanced tips for better results.

• Mid-way photoperiod switching

Consider experimenting with mid-way photoperiod switching. For example, starting with 14L/10D for the first 28 days of flowering and then switching to 12L/12D can provide the same total light exposure as a standard 12L/12D cycle but may increase your overall yield. 

• Optimize Light Intensity

Ensure your plants receive even light distribution. Use reflectors and supplemental lighting if necessary to prevent shadowed areas and promote uniform growth.

Light is the primary energy source for your plants. Ensuring all parts of the plant receive adequate light helps maximize photosynthesis and bud development.

• Watering Techniques

Make sure your plants have the appropriate amount of water as your plants enter the flowering stage. Ensure good drainage to prevent root rot and other water-related issues.

Flowering plants need more water to support bud growth. Proper watering techniques help maintain plant health and prevent issues like root rot.

• Pruning and Training

Use a combination of high-stress training techniques like topping and super cropping and low-stress training like tying down the branches to prune and train your plants. 

The main goal of pruning and training is to achieve an even canopy that maximizes light absorption, promoting health and bud growth and reducing the risk of mold and mildew. 

Frequently Asked Questions (FAQs)

Have a few more questions? We’ve gathered some of the most common inquiries to help you along the way.

How long should I veg my plants for optimal yield?

The vegetative period can last anywhere from 3 to 16 weeks, depending on your goals and growing conditions. For larger yields, consider a longer veg time, but ensure you have enough vertical space to accommodate the plant’s growth during the flowering stretch.

Can I switch back to veg if I accidentally flipped to flower too early?

Yes, it is possible to revert your plants back to the vegetative stage by returning to an 18/6 light schedule. However, this can stress your plants and may affect their overall health and yield. 

If you find yourself in this situation, proceed with caution and monitor your plants closely for any signs of stress.

What are the signs that my plant is ready to be flipped to flower?

Look for healthy, vibrant plants with strong stems and an established root system. 

Your plants should be at least a third of the final desired height, and if you’ve been training or pruning, ensure they’ve had time to recover. Nodes should be alternating rather than opposite, indicating sexual maturity.

Final Thoughts

We’ve shared our own experiences, tips, and lessons learned to help you avoid common pitfalls when switching from veg to flowers. Every garden is unique, and what works for one setup might need tweaking for another. 

Keep experimenting, stay vigilant, and most importantly, enjoy the process.

At Homegrown Cannabis., we’re dedicated to supporting growers like you with top-quality cannabis seeds and expert advice. Go shop for our premium seed selection, tailored to ensure robust plants and generous yields. 

Visit Homegrown Cannabis. to browse our catalog of high-THC cannabis seeds that are easy to grow and take your cultivation to the next level!