Cannabis Veg Room Design

The Veg Room is where baby plants from the Nursery become teen plants and are grown to maturity before being moved into the Flower Room. The majority of the cannabis plants leafy growth and elongation will occur in Veg, however stretching will continue for 2-3 weeks into a 12/12 photoperiod (Flower) where they’ll grow another 30% in size before shifting energy to flower mass production.

Written By Celia Daly
June 11th, 2015

The Veg Room is where baby plants from the Nursery become teen plants and are grown to maturity before being moved into the Flower Room. The majority of the cannabis plants leafy growth and elongation will occur in Veg, however stretching will continue for 2-3 weeks into a 12/12 photoperiod (Flower) where they’ll grow another 30% in size before shifting energy to flower mass production.

Veg Room Set Up

Not allocating enough space for the Veg Room is a typical mistake new commercial growers make. A good rule of thumb is that between 10-20% of your total light wattage in the Flower Room will be used in vegetative growth. This means that if there are 50,000 watts in the Flower Room, there should be between 5,000 and 10,000 watts in the Veg Room.

Ideally, the Veg Room should be set up to include a mixture of two level pallet racking and single level pallet racking. This allows plants to be moved around as they grow and save space at the same time.

The two level pallet racking should be equipped with three to four t5 light fixtures or 800 watts of LEDs per 4×8’ tray. The single level pallet racking should include 4×8’ trays with two m1000w dimmable MH lights, four ceramic MH or 1200-1500 watts of LED per tray.

Light Cycle

While in Veg, as in Nursery, a light cycle of 18 hours on and 6 hours off is the traditional approach. This mimics the natural light cycle a cannabis plant would receive in the wild during this stage of growth which keeps the plants from generating flowers. The problem with this light cycle is that some plants stress under strong lighting for 18 straight hours (this is not a problem in the Nursery because the lights are not as strong). Alternatively we recommend a 6 hours on, 2 hours off cycle 24 hours a day.

This gives the plant a 2 hour break from intense lighting every 6 hours. The flower cycle trigger is 12 hours of darkness, so you shouldn’t see any early flowering problems reducing the dark cycle from 6 hours to 2 hours. As an added benefit, plants can be given more intense lighting with this light cycle and will ultimately be healthier from a less stressful environment.

If there is, or is potential for, heat troubles in the veg area, this 6 on, 2 off light cycle can really help – the 2 hour break gives the cooling system a chance to cool the space back down before the lights come back on.

Moving Plants

When the plants are transferred to the Veg Room from the Nursery, they should be up-planted into one-gallon pots and placed under a light on the double level racks in the Veg Room. At this stage, plan for a one square foot area per plant – this means that a double level area with a 4×8’ tray can hold 64 plants. These plants should be ready for transplant again in 1-2 weeks. 30-40 percent more plants should be moved from Nursery to Veg than will ultimately be needed for Flower.

After the one to two week growth period, up-plant again to 5-gallon containers and move plants to single level racks. Due to growth, only 18 plants will now fit on each 4×8’ tray. Once again, plan for 20-30 percent more plants than will be needed in the Flower room.

When up-planting in a soil/soilless medium, always break up the root ball; this is very important for new root growth and is a technique that has been used in big ag for decades.  Taking care not to break roots or stress the root ball, gently break up the dirt and roots with your hands so that the root system no longer maintains the shape of the previous container.  This is also a good time to introduce mycorrhizal fungi and bacteria to the root zone to promote rapid healthy growth.

Plants should remain in the 5-gallon pots for another one to two weeks before they are up-planted once again to 10-gallon pots. This is the final stage before they head to Flower in another 1-2 weeks. While in 10-gallon pots, 8-10 plants will take up an entire 4×8’ tray and there should be 10-20 percent more plants than are needed for the Flower room.   During this stage of growth, the roots are allowed to fill the new container volume which provides the potential for a high yield in Flower.

The final plant culling happens just before plants are moved to Flower. At this point, only keep the healthiest, heartiest plants and discard anything that remains. If you are doing a great job, then you will be throwing away healthy plants (which is always the goal because you have consistently kept more than were needed for the next stage of growth). All plants that move onto the Flower room should be extremely healthy, not showing signs of deficiency/toxicity or pest/bacterial/fungal infestation in order to produce the best possible buds.


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