Tricks and Tips to Ensure Optimum Flower Yields

To get optimum flower yield from your plants several important factors need to be considered. These are:

  • Genetics must work for you. Don’t speculate on taking a chance with some seeds that you’ve had lying around forever. Source good plant genetics. This is the most important factor of all because this is where it all begins.
  • Uninterrupted Dark Hours. THIS FACTOR IS VERY IMPORTANT!  Much of the flowering process occurs during the plant’s night time hours. Photoperiod plants require uninterrupted dark hours. What this means is the flowering process will be interrupted if any light enters the room during the plant’s night time hours. For this reason, it is important that you do not interrupt the night cycle by entering the room during the lights off period. In addition to this, ensure that light (artificial or sunlight) is not finding its way into the growing environment during the lights off period.
  • Healthy root systems promote healthy flowers. (read more on this here)
  • Balanced nutrition promotes healthy growth.
  • Environmental conditions (light, humidity, air movement, CO2 availability, temperature, water/oxygen ratio of medium) must be ideal to achieve genetic potential.
  • Flowering additives used with careful consideration can add density and weight to flowers. Please, however, don’t go too crazy with additives. One of the most common mistakes that indoor growers make is mixing too many additives without even understanding what is in them. Don’t get sucked in by flavour of the month additives that some supplier is talking up. Establish why the additive can help the plant before you purchase it. I highly recommend using P-K (Potassium and Phosphorous) additives during the flowering cycle. Use only after the stretch cycle (1-2 weeks after switching to 12/12) and when bud set has begun. Additionally, I highly recommend using silica throughout grow and bloom. Other additives that can/will aid optimum flower yields are Triacontanol an plant hormones such as brassinosteroids. The latter two are only required at extremely low levels. (read more about beneficial additives here)
  • Photosynthesis. Don’t go cutting leaves off your plant in the misguided notion that this will allow more light to the flowers – hence give you a healthier yield. Leaves are sugar production factories for the plant. Cutting them off reduces the plant’s capacity to photosynthesise. Only when the leaves are yellowing and dying should they ever be removed.
  • Increased CO2 Levels: As of November 2011, carbon dioxide in the Earth’s atmosphere is at a concentration of 390ppm by volume. However, plants benefit from much higher levels of CO2 than is naturally present in the atmosphere. Research has shown that C3 plants have a CO2 saturation point of between 1000- 1500ppm, with 1200- 1250ppm likely being the most suitable range for indoor crops. Suman Chandra et al (2008) demonstrated that cannabis sativa yields were significantly enhanced at even 750ppm of CO2.

  • Tie your plants down (SCROG). Keep them at a reasonable height. Generally plants are kept relatively close together and as they get bigger they compete for light. In addition to this HID lighting has limited depth of penetration where lumen output (light intensity) is concerned.  The most effective way of bending or tying your plants is by covering their grow area with taut flower net (a frame to hold the net tightly in place is handy for this). The net should be placed approximately 6 – 8 inches above the system. As the plants grow bend them under the net to take advantage of the lit area. By bending the plants this way the secondary nodes take off towards the light and become rods of flowers. The 6 – 8 inch measurement is suitable for plants that will finish at 2 – 2 1/2 foot. Adjust accordingly for larger plants.
  • Flower development = light availability (depth of penetration and intensity). A common mistake that beginner growers make is growing plants too high and/or growing too many plants within too small an area. Too many plants competing for light will receive high light levels only on the very tops of the plants. As a result of this there will be flower mass on top of the plant/s with very little flower development lower down. It is more productive to have fewer plants that are receiving adequate light levels to promote even flower set from the bottom to the tops of the plants. Similarly, plants that are too tall for the available light will receive high light levels (levels that they need) only high up on the plant. Again, flower-mass will only occur high up on the plant. This is why experienced indoor growers generally grow shorter plants, or where large plants are grown they are tied down to keep them short and wide.
  • Lighting to Optimize Yields: The light energy required by plants is confined almost entirely to the visible spectrum of light (400nm – 700nm). While there are key points within this spectrum (435nm and 675nm etc), growth is optimized under the entire range of the spectrum. This is because different color wavelengths stimulate different biochemical reactions within the plant. As a result of this, different physiological functions are activated and energized, which – in turn – determine plant growth rates and formation characteristics.Photosynthesis depends on the energy created by a combination of both light intensity and color. Growers who have experimented with different lighting combinations can/will tell you that different lighting configurations can produce very different results. For instance, plants that are flowered under a combination of red spectrum (HPS) and blue spectrum (MH) lighting form very differently than plants that are flowered under red spectrum light alone. For instance, a plant that is flowered under HPS light alone typically ‘stretches’ (becomes unnaturally elongated). This is because, while HPS provides large amounts of yellow and red light it tends to be lacking in other key areas of the visible color spectrum. This means that the required stimulus for the various biochemical responses is not adequate. By introducing blue spectrum light into the red spectrum we are able to cater more adequately for these biochemical responses. In short, blue spectrum light promotes a better plant structure (shorter/stockier plant, smaller gaps between nodes) while the red spectrum light provides stimulus for flower growth.
  • Night and Day Temps (Thermoperiod) The differences in temperature during the day/night (light/dark) period, known as “thermoperiod”, have a major effect on plant growth. It is assumed that through a raise in temperature early in the night period, more energy is put in generative growth (flower development). However, higher temperatures during the night period, compared to the day period, will stretch internodes and vice versa. Therefore, it is critical to reduce night temperatures to that of day temperatures during the stretch and bloom period. It is generally asserted that plants produce maximum growth when exposed to a day temperature that is about 10 to 15°F higher than the night temperature. This allows the plant to photosynthesize (build up) and respire (break down) during an optimum daytime temperature, and to curtail the rate of respiration during a cooler night. High temperatures cause increased respiration, sometimes above the rate of photosynthesis.
  • Plant Spacing: One of the most common mistakes made by indoor gardeners is that they fail to appreciate that fewer plants can mean more yield. Too many plants crowded into a small space will compete for available light and as a result stretch as they compete. Other than this, plant crowding will result in all of the plants shading the bulk of one another out, which in turn will result in each and every plant performing well below optimum photosynthetic potential/levels.
  • Healthy plants throughout Grow and Bloom. Ensuring that your plants remain disease free, insect free and fungus free, with healthy root systems, optimum environmental conditions, balanced nutrition and careful use of additives from cloning to finish will greatly aid your final yield.
  • Don’t pick too soon. Flower weight increases in the last 2 weeks of flowering. That is, the flowers may look big but cellular activity may still be taking place. The flowers increase in density and weight as long as cellular activity is taking place.


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