What’s the proper Veg PPFD. Well, depends on your goals – according to this study 600 – 900 ppfd or even higher (1000+ ppfd) if you want compact plants (Vertical Growers). Study HERE
If you are attempting to keep your plants compact, before the flower stretch, a blue enhanced spectrum, such as the Mammoth Veg Series, + Heavy Light will maximize the plants morphology to be compact with the most bud sites.
Few lighting companies recommend the correct lighting (ppfd) targets. That is either because (1) their lights are not bright enough, (2) they do not understand the latest academic research or (3) they work with novice growers. All ok - but Mammoth Lighting will continue to present research to maximize the growth of this plant for the experienced and pro growers.
We work with the world’s largest Vertical Growers and this is the type of research and analysis that is presented. Yours for free. Enjoy.
Light Intensity, Spectrum and Plant Morphology.
Light intensity is one of the most important environmental factors for plant growth. We have shown multiple studies of Cannabis yield being Linear to Yield (Zhen 2021; Eaves 2019; Bugbee). For the most part, light intensity effects yield and spectrum effect plant morphology and cannabinoid production. However, we can steer the plants morphology with light intensity.
If you are a Vertical Grower or have limited space – you should be pushing your plants with heavy light in Veg and with a Blue enhanced spectrum to maximize your space. Vist the website for this full study.
In contrast with high-intensity light, low-intensity light is frequently reported as a factor for photoinhibition (Long et al., 1994). In addition, the effect of low light levels on plant growth and photomorphogenesis is well known; for example, they can lead to plant stretch or increase height (Fan et al., 2013; Steinger et al., 2003).
It’s preferable to utilize a light that has both cool (5000k) and warm light (3000k). A larger proportion of blue light has an inhibitory effect on cell elongation, which leads to shorter stems and thicker leaves. Conversely, a decrease in the amount of blue light will cause a larger leaf surface area and longer stems. Too little blue light will negatively affect the development of plants.
Numerous studies have shown that increasing blue light can reduce stem length and leaf area and increase leaf mass area for different crop species (Cope and Bugbee, 2013; Hogewoning et al., 2010a, 2010b; Li and Kubota, 2009; Trouwborst et al., 2010)
Blue light has been shown to decrease internode length and enhance compactness of various species (Dong 2014, Khan 20111), whereas far-red and green wavelengths have been shown to induce shade avoidance syndrome symptoms, including stem and leaf elongation and premature flowering [Franklin 2015].
In Cannabis, plants grown under LED were shorter and more compact compared to those grown under the red HPS treatment (Magagnini 2019).
Previous studies by Tibbitts et al. [Tibbitts 1983] and Wheeler et al. [Wheeler 1991], who reported that plants grown under sole HPS light may suffer from unbalanced morphology expressed by excessive leaf and stem elongation.
This is due to the low R:FR ratio (i.e., the ratio between red and far-red light) and low blue light emission of the HPS lamp. The low R:FR ratio increases the activity of several transcription factors that activate genes involved in auxin biosynthesis leading to faster stem elongation [Ballaré, 2014]. Blue light regulates morphological responses such as shoot and internode elongation, shoot dry matter, and leaf area expansion [Huché-Thélier L, 2016].