Cannabis is a photoperiodic plant. Outdoors, cannabis plants initiate flowering after the summer solstice when the days start becoming shorter. Indoors, it takes more effort. When growing cannabis indoors, few things are more exciting than seeing your plants start to flower.
Indoor grows let you control when plants start flowering since you decide the light/darkness schedule. With power comes responsibility, and while flipping too soon means wasted space and reduced yields, leaving it too long means your cannabis plant may outgrow its tent and/or get too close to the lights.
Like most aspects of cannabis cultivation, there’s no exact method or one-size-fits-all approach, although there are some recommendations. Your setup, cultivar selection, and grow techniques can all impact the decision of when to move plants to flower. In this article, we’ll review simple methods that ensure the smoothest flip to the flower stage.
TL/DR | Key Takeaways:
Keep your plants in the vegetative state for 2-8 weeks or an average of 60 days.
Get to know what you grow: plant type (Sativa/Indica), age, height, and whether you are growing from clone or seed all matter.
Low and high-stress training techniques help keep your plant size in control
How Long Should You Veg Your Weed Plants?
During vegetation, roots and shoots grow constantly, gathering nutrients for growth and photosynthesis to produce beautiful flowers. Keeping the lights on for 18 hours (and off for 6) creates an environment that mimics long sunny days, helping the plants thrive and mature. While this can be continued for quite some time to create monster plants, most growers don’t have the luxury to grow trees. Space and resource constraints mean you can only push plants so far in an enclosed area before they need to be flowered.
Flipping your plants, or switching the light cycles, reduces the hours of light. It’s similar to fall weather because it signals the end of the season is near. The change in light exposure kickstarts flowering, transitioning the plant’s main focus to creating buds instead of vegetation growth.
In general, the vegetative stage should be 2-8 weeks (~60 days), but it can continue for many weeks after that if needed. It’s not a clear-cut answer because your specific environment limits the ultimate plant size.
Remember, cannabis plants aren’t done growing just because you’ve switched them to flower. Expect your plants to at least double in height during the flowering stage. However, you need to time it right. Making the decision too late could ruin a harvest as the plants will outgrow their enclosure.
Below are some factors to take into account when flipping your cannabis plants.
Did You Plant Cannabis Seeds or Clones?
Your methods of propagation impact veg timing. You can flip well-rooted clones almost anytime. Gently pull on the clone internodes at the base of the stem to ensure they are ready and/or check the bottom of the cubes for good white healthy root development. If you pop seeds, they need 2-4 weeks to develop a root system that can support flowering.
Cannabis plant in a soil block with exposed roots.
Are Your Weed Plants Sativa, Indica, or Hybrid
The type of cannabis cultivar you’re growing will also impact the decision of when to flip plants. Indoor space is usually limited by height and light distance. It’s also important to take different genetic makeups into account. Depending on what you are growing, the amount of stretch will vary when flowering:
A dominant sativa strain will grow up to 250% of its veg size during flower. It’s important not to let it veg out too much so you don’t run space under your lights.
Indica cultivars can be left to veg longer. A strong indica will grow during flower but only up to 50% of its original size.
Hybrids will reflect different traits based on their lineage. As a rule of thumb, plants should almost double in size during the flower cycle.
Should I Flip my Autoflowering Strains?
While you can do this, it is not recommended. Autoflowering plants don’t need the darkness to signal flowering, as they flower based on age. It’s best to let your autos continue blooming through an 18/6 light cycle. You can find our Autoflower seeds here.
Consider the Size of Your Grow Tent When Timing the Flip
Plant height must be controlled for most home growers and even some professional setups. While it’s great to have massive plants, it’s sad when you run out of space before flowering is complete. The size of your grow space is extremely important and cannot be ignored when making this decision.
Expect your Cannabis Plants to Stretch After Flipping
Again, your plants are not done growing just because you flipped the light schedule. Most cannabis plants will double in size during flower.
You can use height to determine the right time to flip plants into flower. Taking your maximum canopy height into account, you want to flip a cannabis plant to flower before they reach just below 50% of that height, potentially earlier if they’re sativa dominant.
Marijuana plants set to transition to the flowering phase.
Can you Train Your Cannabis Plants After the Flip?
High-Stress Training techniques (HST) are great ways to keep the canopy and plant size under control. If needed, perform this well before the flip. You should only use low-stress training (LST) methods (if necessary) once you have switched to flower. You want your cannabis plant to focus all its energy on flower development instead of bouncing back from stress.
If you notice your plants are getting too tall for your grow space, there are different ways to train them.
The Sea of Green
The Sea of Green (SOG) method lets you grow multiple smaller plants on a shorter veg cycle. This means there’s much less potential for outgrowing your environment when running SOG.
Sea of Green (SoG) Method for Cannabis plants.
Screen of Green
Screen of Green (SCROG) lets growers set their canopy height by using a screen or net across their plants. This provides tie-down points and the option to weave and train the plant across the screen, reducing the impact of vertical growth while in flower. SCROG makes it easier to grow bigger plants in tents.
Screen of Green Technique for Cannabis Plants.
Lollipopping
Lollipopping or undercutting your plants is a great way to direct their resources toward the most important growth: the buds! The plant’s lower branches can be pruned clean in the early flowering stage. This means any extra growth happening during flowering is all in and around the nugs. It also has the added benefit of providing good airflow while reducing popcorn buds.
Pruning a Marijuana Plant by Lollipopping.
Super Cropping
This high-stress training technique should only be done in veg. When super cropping, the stems of the plant are bent or crushed without snapping or breaking them completely. This reduces plant height and adds some healthy stress to the plant while opening up the canopy to the lower branches. Doing this is a little risky, but it can increase yields by up to 20%.
Optimizing Cannabis Growth with Super Cropping.
Topping
Topping can be a great way to reduce vertical growth for your plants and promote fuller development of mid and lower branches. It will also increase yields, but it needs to be done in early veg, not flower.
Comparing the Difference Between Apical and FIM Topping Techniques
Checklist to Flip Your Cannabis Plants from Veg to Flower
Flipping from veg to flower might seem as simple as changing the settings on your light timers. However, there are a few factors to consider besides the light schedule. Here’s a checklist that helps ensure a smooth flip of your weed plant:
Should I Flip My Outdoor Weed Plants?
Outdoor plants don’t need flipping as they’ll respond naturally to the growing season. However, you can consider light deprivation techniques for outdoor grows to potentially get two harvests or more out of a season. Do this by building a structure over your plants or by pulling tarps over them to provide 12 hours of darkness even when they wouldn’t normally get it.
Flipping your Cannabis Plants Early Will Avoid Common Issues
Timing the flip is part art and part science. The biggest mistake that can happen is underestimating plant growth during flower. Your plants will grow, and in some sativa cases, they’ll grow a lot. So, to be safe, flip early, not late!
Cannabis plants overgrowing in a grow room
Conclusion
While it’s common to say ~60 days or 2-8 weeks is the right time to flip plants from veg to flower, your environment, plant genetics, and context control when this decision needs to be made for each cultivar. Plant age and plant height are also key to timing the flip.
Plan for at least a doubling in height and an increase in plant mass during flowering, and use HST or LST to manage your available canopy. Please share any questions or methods that worked well for you, leaving a comment below!
Keep on Growing!
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