BTW - just posted an article at
Covers natural ways of controlling stretch. It's a work in progress and I'll add more shortly to it. We're doing some research with cytokinins to see how they reduce stretch. Any feedback (good and bad) I'd be more than happy to hear. We're SEO optimizing the site now so the link may change. If this happens just go to
www.manicbotanix.com and you'll find it in the articles on the site. Here's an excerpt that goes through natural ways of controlling plant height and minimizing stretch. I'll be adding a bit more to this soon.
Reducing Stretch Naturally
Various factors such as plant hormones, light, carbon acquisition, and nutrients influence the amount of stretch (apical dominance) a plant will exhibit during its life cycle. Because of this, stretch can be reduced if the right practices are implemented in the grow room.
SCROG (Screen of Green)
Scrog is a term used in the indoor growing of cannabis. The plants grow up to the screen and then are "trained" or tied to the screen, resulting in a flat table of plant growth. Through this means plants can be trained/tied out to remain shorter than they normally would grow. Another advantage to scrogging is because all the buds are growing at about the same height, it is possible to get all the growth within the effective circle of light from the lamp, resulting in increasing yields within a given space.
Tipping/Topping
Apical dominance (stretch) is caused by the apical bud (top shoot of the plant) producing IAA (auxin) in abundance.
When the apical bud is removed, the source of IAA is removed. Since the auxin concentration is much lower, the lateral buds (side shoots) are stimulated to grow. Thus, decapitating (pruning) the top of the plant will cause it to branch, reducing upward growth.
Due to this tipping/topping is a good technique, along with scrogging to control plant height.
Flipping Times and Understanding the Genetics You Work With
This is a tricky one as different people will use different techniques of growing. Some people will grow small plants in numbers while others will grow just one large plant etc. Also, different plants (genetics) will do different things. One type of plant may be very explosive and another type may not have the same vigor. One strain may be far leggier than another. Getting to know your strain will help you fine-tune the finishing height.
As a rule of thumb - the plant does 80% of its growing during the 12 hr light cycle. So be wary. Don’t think that you have to grow a plant in the 18-hour light cycle for too long. As a general rule if you switch down an 8 - 10inch plant you will finish with a 2 1/2 to 3-foot plant.
Know your plant and flip at the appropriate time!
Genetics! Genetics! Genetics!
Genetics play a major role in plant characteristics. In very simple terms, sativas are a much ‘leggier’ plant than indicas and hence indicas, or indica dominant indica/sativa crosses are better suited to indoor growing environments.
Lighting
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.
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.
Night and Day Temps
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.
However, not all plants grow best under the same range between nighttime and daytime temperatures. For example, snapdragons grow best at nighttime temperatures of 55°F; poinsettias, at 62°F.
Optimum temps in cannabis have been shown to differ based on genetics, the origins of these genetics, and the environments in which they evolved. For instance, in research conducted by F.A. Bazzaz et al (1975),
