Transitioning From 18/6 to 12 and What to Know
When an indoor grower switches their timer from 18/6 to 12/12, the plants will respond to the difference in darkness by beginning to flower. It is during this time when cannabis plants will make one final effort to stretch for the sky before they start producing pre flowers and buds. In this article, I will explain all you need to know about the transition stage, what nutrients to use, what to expect from different strains and my top tips to help prepare you to grow the ultimate crop!
What is the transition phase, and what should I expect?
This basically refers to the time when plants begin to stretch and will double or treble in height. As cannabis plants respond to the reduction in the darkness period by 6 hours, they will be triggered to release growth hormones and auxins in an attempt to grow as close to the light source as possible.
Not all plants will react the same once they start flowering, and below is a better explanation of how certain strains will respond to 12/12.
Indica
Indica cannabis plants have a tendency to stay low and squat during the vegetative stage, and will usually double in height by the end of the third week of flowering. Short indica plants will be best suited for growers with limited height and space, as they will usually finish around 125 cm tall.
Sativa
Out of all the different cannabis plants, sativa strains will stretch and grow excessively tall during the flowering period. In some cases, indoor sativa plants can grow up to 9 feet tall, and demand between 11–13 weeks before they are ready for harvesting. Only growers with experience, and the room to grow should attempt flowering a sativa.
Hybrids
A mix of indica and sativa genetics, hybrid cannabis plants will typically stretch enough to cause plants to double in size. Combined with plant training late in the vegetative period, it is possible to keep hybrids relatively low and close to 125–150 cm tall.
Autos
Autoflowering cannabis seeds will grow to around 120 cm tall. When grown indoors, autos are an excellent choice for growers who want solid yields, and a low profile crop.
Do I need to change the light intensity during the transition phase?
Cannabis plants will be able to use more light during the transition and flowering phase, compared to the vegetative period. This means if you are using dimmers, then providing full power is a good idea.
If you are not using dimmers, then you can always lower the lights to make them closer to the top of the canopy, increasing light intensity. You should aim to have your grow light 60-75 cm away from the top of the plants for the best results.
What about changing the nutrients?
I find that using the same nutrients that were used during 18/6 until the start of week 3 of 12/12, is the ideal feeding regime. Remember at this time the plants are using all their energy to grow as tall, bushy and wide open as they can, and won’t be focusing on flower production, until week 3 onwards.
Using liquid nutrients or powdered feeds designed for the flowering period from day 21 of the flowering period, from my experience, is the ideal time to switch. By this time, the high amounts of P and K will encourage a massive amount of pre flowers, resulting in fast flowering plants.
Lowering the humidity levels down to 50%
When flowering cannabis plants, it is important to keep the temperature and humidity level within a certain range. Relative humidity can be reduced down to 50% over the flowering period. Additionally, there should be a good quality of air flow, providing a consistent air current and plenty of fresh air.
Top tips for when you transition to flower
If you are a first time grower and have no experience stretching cannabis plants, then below are some of my top tips that should be considered. These will help you get the most out of your indoor grow space and produce the best plants.
Top tip #1 - Train plants before 12/12
This tip is for sativa dominant plants that want to stretch as tall as the ceiling. You can train the plants one week before flowering them by tying them down and topping them. This simple but highly effective technique will help significantly reduce the final plant height, making it easy to work with and maintain.
Top tip #2 - Do not overfeed
Changing your timers over to 12/12 is one of the most exciting times for a grower, and can often be a reason why first time growers may overfeed their plants. My tip here is to use the same amount of water and nutrients as during 18/6 for the first 14 days of the transition phase. Do not overfeed or over water, and make sure you provide all the nutrients and trace elements they require.
Top tip #3 - Flower your plants at nighttime
Running your flowering room at nighttime from 10pm until 10am is a great way to ensure cooler temperatures. This tip is particularly beneficial to growers who suffer with high temperatures during the daytime or are battling Summer heat waves. Electricity tariffs are also cheaper, so there are several benefits to flowering your cannabis plants in the nighttime.
My conclusion
Growing healthy, strong and bushy plants with a well established root zone during the vegetative stage, is very important and will play a massive role in how they flower. Growers with limited height and grow space should choose to work with indica or auto-flowering genetics.
Experienced growers will be able to grow hybrids and sativa strains, however should be well-equipped to deal with excessively tall plants. Every plant will react differently, and my advice is to grow out as many different strains as possible, and learn about each that way. Good luck flowering your indoor plants and growing the ultimate harvests!
S
Stoney.Tark
