A Beginner’s Guide To Flowering Cannabis

17 Feb 2022

There is nothing more exciting as a beginner grower to switch your timers over, and prepare for the next few months. During this time Cannabis plants will produce flowers which will become the Cannabis buds that you will dry out and cure in jars. In this article we explain all you need to know about the flowering Cannabis.

Extended Darkness

Since your seedlings started life, they would be growing under an 18/6 lighting schedule. This is done to mimic the long days of the Summer months and for plants to remain in a vegetative state. As Long as the plants receive less than 12 hours of darkness they will remain this way and how mother plants are kept alive for so long.

As Cannabis plants are given 12 hours of darkness, this will begin a chemical change and for the plants to now produce flowers. This is what is responsible for plants stretching upwards and growing 2-3 times their initial height. Once the timer has been changed to 12/12, it is not advised to change the timer back to 18/6 as this may cause stunted plants.

  • The timer should now be set to 12 hours of light and 12 hours of dark.
  • Make sure that your timer segments are firmly pressed down.
  • It is a good idea to have a back up timer in the event of an emergency. 

More P and K

Cannabis Plants require more Phosphorus and Potassium during the flowering period. Most liquid nutrients designed for the vegetative stage will be high in Nitrogen and lower in Phosphorus and Potassium. 

During the first 2 weeks after the timer has been changed, many growers like to continue feeding a high Nitrogen liquid feed. Once the Cannabis plants have fully stretched after 21 days, it is better to use the flowering feeds which will be higher in P and K. You should be able to follow the nutrient feeding chart provided by the brand and use this as a guide to grow the best Cannabis buds.

Temperature and Humidity Levels

This plays a major role in how well your plants will perform and the quality of the Cannabis buds. Whilst growing under the 18/6 light regime, the recommended temperature and humidity levels should be 24 degrees Celsius and around 65-75% humidity. When flowering Cannabis however, the humidity levels need to reduce to the point of the environment becoming dry. Normally, this is close to the 30-35% humidity mark, and this dry zone also encourages plants to produce more resin and grow tighter Cannabis buds.

Pathogens such as mold and powdery mildew can infect a garden full of flowering Cannabis plants, and the main culprit is high humidity and poor air circulation. Once these airborne pathogens attack your plants, it can be very difficult to fully remove so operating in the safe zone of 30-35% relative humidity and a lights on temperature of 75 degrees Fahrenheit (24 degrees Celsius) is best for Cannabis buds.

  • Hygrometers will provide a digital reading of the temperature and humidity.
  • Poor air flow is one main cause of mold and mildew.
  • Spider mites prefer hot and humid conditions also.
  • Oscillating fans are the best way to keep a fresh air flow.
cannabis flowering guide

The Stretching Phase

Growth hormones inside the plant are responsible for the stretching that occurs within the first 2-3 weeks. Cannabis plants will take this time to grow as tall and wide as possible to get as close to the lights as possible. 

Indica Cannabis plants will usually stretch twice their original height and are better suited for growers with limited height. Sativas on the other hand will tend to grow tall and lanky, requiring support from bamboo canes or a trellis. 

Pre Flowers Appear

It is around the 14-21 day mark where pre-flowers will emerge revealing their sex. Males plants tend to produce pre-flowers slightly earlier than females, however when growing with feminized Cannabis seeds or clones, there is no need to worry about sexing and removing male plants.

Female pre-flowers will look like a white hair and as they cluster grow closely together. From this white hair known as a pistil, the Cannabis buds will develop, so the more pistils that can be seen can be an indicator of the production value. It is actually these white hairs that come in contact with male or feminized pollen that create Cannabis seeds.

  • Once pre flowers appear, it is advised to use a P-K nutrient.
  • Cannabis buds will form between the internodes and stems. 
  • Pistils will turn brown as the Cannabis buds mature.

Time To Flush

Once you have surpassed the first 3 weeks and are now seeing pre flowers forming into buds, you will have a 3-4 week period of feeding flowering nutrients, before flushing. This means that for the final 2 weeks of the flowering period, you will cut off all nutrients and feed only water.

The main reasons for this is to allow any built up salts around the roots to be washed away and used, and to also encourage the Cannabis plants to use their internal reserves. Flushing Cannabis buds has many benefits and will result in a much smoother and more enjoyable smoke and better tasting flavors.

When To Harvest?

You may be working with the flowering time provided by the seedbank, however there are a few checks that should be done prior. Knowing the right time to harvest your Cannabis buds should be down to the following factors:

  • Trichomes are mostly silver with some amber and red trichome heads.
  • Pistils have turned brown and there are almost no white hairs.
  • The calyx has become swollen and the buds have a hard density.
  • The terpenes are their most aromatic.
  • The plants are completely flushed and leaves have faded in color.

Mistakes To Avoid with Flowering Cannabis Plants:

  1. Cold temperatures can cause plants to become stunted and grow slowly. This can be very discouraging as a beginner grower and can be easily fixed by using a heater during the lights off period. Do not let the garden drop lower than 16 degrees Celsius and invest in a hygrometer to get a digital reading. 
  2. Poor air flow is the number one cause of rotting buds and leaves covered in powdery mildew. Spider mites will thrive in hot and humid environments so if you find you have either of these three, then the temperature, humidity, and air flow will be mainly responsible. 
  3. Rushing your crop in order to meet a deadline or just down to inexperience is not advised. Be patient and wait until the Cannabis buds are fully formed and hard to squeeze. 
  4. Hammering the Cannabis plants until the harvest date will only result in a harsh smoke that burns with charcoal-black ash. This is the main reason flushing is done and neglecting the flush is not advised. 

Also read on Soft Secrets:

10 Top Tips on Growing Auto-Flowering Cannabis Outdoors

- What Happens When Cannabis Enter Flowering?

How to Perform Monster Cropping?