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MythPuffers: What’s The Deal With Stems And Seeds?

We all know what it’s like to spend 60 bucks on a disappointing eighth of weed that’s way too stemm-y and chock full of seeds. While it’s not only a hassle to de-seed and de-stem the sub-par product, what you’re left with once your eighth is gone seems entirely useless — but somehow you convince yourself to save it all anyway.

It’s been posited by some potheads that seeds and stems contain no THC, taste like shit, and will make you sick or even infertile. More positive stoners, on the other hand, have faith in the byproducts’ heightening abilities and promote the smoking, drinking, and planting of stems and seeds. Obviously when it comes to drugs like marijuana, everyone reacts to these things differently, but that, my friends, is how legends are born. This week’s MythPuffers is seed-and-stem-centric — focusing on not one but three common myths and questions surrounding the two little things potheads dread most.

One of the more popular ways to rid of seeds and stems is to smoke them — un-ground in many cases. One myth that has spurred from the smoking of these stems and seeds is that they will negatively affect your fertility. What? That’s right — some people believe that smoking stems in particular will lessen a male’s sperm count and damage a woman’s ovaries.

While this may seem ridiculous at face value, according to BBC News, a study at Buffalo University has linked chronic marijuana smoking to a lower sperm count among males. Head researcher Dr. Lani Burkman claims that THC is “doing something to sperm” — something which makes the little guys swim too fast so that they end up getting tired before finishing the job. In terms of female fertility, however, results from a separate study are inconclusive.

While this may not be great news for all the pot head dudes out there, it turns out smoking stems and seeds doesn’t really matter because smoking weed in the first place is what affects sperm count. Therefore — since smoking stems tastes disgusting and your sperm is going to die anyway — why not consider something like stem tea?

Not only is stem tea easy to make but, also, if done correctly ,it’s a great way to get rid of saved stems. While some might believe that stem tea is a sham after learning last week that THC is not water soluble, there are several recipes available on the Internet (like this one) which suggest steeping your pot in something fatty, like milk, or for the hard-core tea drinkers, something alcoholic. Although stem tea will not produce a high as strong as one from smoking — leaves, not stems — there are traces of THC in the stalks and thus drinkers will experience mind alterations if the beverage is prepared correctly.

Now that your stems have been taken care of, what about your seeds? One of the most popular myths — or hopes rather — is that planting seeds found in dumpy weed will grow into beautiful marijuana plants.

It probably comes as no surprise that, yes, by planting seeds found in shake, it is possible to grow marijuana plants. While this seems like an attractive idea in theory, what many stoners don’t realize is the time and effort that goes into cultivating reefer. Especially if you’re living in New York, as a college student, there’s nowhere in the city a plant would have access to proper soil and enough sunlight to prosper — this, of course, is a lot for any smoker. Despite the fact that potheads aren’t of the most responsible breed, if your weed is shitty in the first place, why would you even want to reproduce it?

Of course, there are many other ways to deal with pesky stems and seeds that are possibly more affective and slightly more reasonable than stem tea and planting seeds. Green Dragon, for example, is a notorious weed, stem, and seed concoction that MythPuffers will be investigating in the coming weeks — so stay tuned.

Vegetative propagation of cannabis by stem cuttings: effects of leaf number, cutting position, rooting hormone, and leaf tip removal

This study evaluated the influence of several factors and their interactive effects on the propagation success of stem cuttings of cannabis (Cannabis sativa L.). Factors included (i) leaf number (two or three), (ii) leaf tip removal (one-third of leaf tips removed), (iii) basal/apical position of stem cutting on the stock plant, and (iv) rooting hormone [0.2% indole-3-butyric (IBA) acid gel or 0.2% willow (Salix alba L.) extract gel]. Cuttings were placed in a growth chamber for twelve days and then assessed on their rooting success rate and root quality using a relative root quality scale. The IBA gel delivered a 2.1× higher rooting success rate and 1.6× higher root quality than the willow extract. Removing leaf tips reduced rooting success rate from 71% to 53% without influencing root quality. Cuttings with three leaves had 15% higher root quality compared with those with two, but leaf number did not influence rooting success rate. Position of cutting had little effect on rooting success or quality. To achieve maximum rooting success and root quality, cuttings from either apical or basal positions should have at least three fully expanded uncut leaves and the tested IBA rooting hormone is preferred to the willow-based product.

Résumé

L’étude portait sur l’influence de plusieurs facteurs et des conséquences de leur interaction sur la multiplication du cannabis (Cannabis sativa L.) à partir de boutures. Ces facteurs étaient les suivants : (i) le nombre de feuilles (deux ou trois), (ii) la suppression de l’extrémité des feuilles (retranchement du tiers du bout des feuilles), (iii) l’origine basale ou apicale de la bouture et iv) l’usage d’une hormone pour accélérer l’enracinement [gelée à 0,2 % d’acide indole-3-butyrique (IBA) ou gelée d’extrait de saule (Salix alba L.) à 0,2 %]. Les boutures ont été placées douze jours dans un phytotron, puis évaluées en fonction de leur enracinement et de la qualité des racines selon une échelle exprimant la qualité relative de ces dernières. Comparativement à l’extrait de saule, la gelée d’IBA améliore l’enracinement par un facteur de 2,1 et la qualité des racines par un facteur de 1,6. Supprimer l’extrémité des feuilles réduit l’enracinement de 71 à 53 %, sans que la qualité des racines en souffre. La qualité des racines des boutures de trois feuilles était de 15 % supérieure à celles des boutures à deux feuilles, mais le nombre de feuilles n’exerce aucune influence sur l’efficacité de l’enracinement. L’endroit d’où venait la bouture a eu peu d’effet sur l’enracinement ou la qualité des racines. Pour obtenir le meilleur enracinement et les racines les plus robustes, les boutures prélevées à la base ou au sommet du plant devraient avoir au moins trois feuilles entièrement développées qui n’auront pas été entamées; on privilégiera aussi l’IBA à l’extrait de saule comme hormone d’enracinement. [Traduit par la Rédaction]

Introduction

Cannabis (Cannabis sativa L.) production for legal markets in North America, including both medical and recreational, is quickly becoming a profitable industry. North American spending on legal cannabis was estimated at 6.7 billion USD in 2016 and is projected to reach 21.6 billion by 2021 (ArcView Market Research 2017).

Cannabis is an annual herbaceous species that has been widely cultivated and used as a medicinal plant since ∼2800 B.C.E. (Russo 2007). Its medicinal value is attributed mainly to a group of secondary metabolites called cannabinoids, which are concentrated mostly in the essential oils of unfertilized female cannabis flowers (Potter 2014). Cannabis cultivation and possession were outlawed in the United States in 1971 and much of the world followed suit soon after (Potter 2009). Since then, some countries including Canada and the Netherlands have relaxed their regulations and implemented programs allowing access to cannabis for medicinal purposes. In these programs, strict safety standards are enforced to control the quality of cannabis being distributed to patients; however, there is little guidance for growers regarding horticultural management. For growers, horticultural guides and online resources are available, but few are based on peer-reviewed scientific research (Potter 2009; Caplan et al. 2017a; Caplan et al. 2017b).

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Based on our communications with Canadian medical cannabis producers and recent reviews on the state of global cannabis production (Leggett 2006; Potter 2014; Farag and Kayser 2015), modern day cannabis production occurs primarily in controlled environments using artificial lighting and either soilless growing substrates (Caplan et al. 2017a; Caplan et al. 2017b) or solution cultures. Furthermore, some medical cannabis growers favour organic production practices because consumers and regulating bodies often demand pesticide-free cannabis. Cannabis is propagated by seed (Potter 2009; Farag and Kayser 2015), vegetative stem cuttings (Coffman and Gentner 1979; Potter 2009), and in vitro propagation (Lata et al. 2009a, 2009b, 2011). Propagation using vegetative stem cuttings is often preferred by cannabis growers. It is a low-cost method that delivers genetically uniform plants with consistent rates of growth and cannabinoid production compared with propagation from seed (Coffman and Gentner 1979; Potter 2009).

To our knowledge, no peer-reviewed research exists on optimizing propagation by stem cuttings in cannabis; however, this method has been investigated in other economically important species such as Pisum sativum L. (Eliasson 1978), Lippia javanica (Burm. f.) Spreng. (Soundy et al. 2008), some timber crops (Ofori et al. 1996; LeBude et al. 2004), and some ornamental nursery crops (Grange and Loach 1985). The primary goal of propagation by stem cuttings is to facilitate the formation of adventitious roots. Several factors have been identified that support adventitious rooting in vegetative stem cuttings (Hartmann et al. 2002). Some of these include leaf area (or leaf number), cutting position on the stock plant, the use of rooting hormones, lighting, rooting medium, water status, and mineral nutrition. The present study focused on the first three of these factors.

Leaves act as sources of photosynthate for cuttings, which is important for successful rooting. Increased leaf area and (or) number may improve the rooting success rate and formation of adventitious roots in cuttings (Leakey and Coutts 1989; Ofori et al. 1996). Leaves also stimulate rooting as sources of rooting co-factors and endogenous auxin (Haissig 1974). Conversely, greater leaf area and (or) number provide a larger surface area for evapotranspiration and evapotranspirative water loss, which may negatively affect rooting success rate (Davis and Potter 1989). A reduction in leaf area may reduce evapotranspiration-induced stress (Leakey and Coutts 1989; Ofori et al. 1996) or avoid crowding in the propagation environment (Aminah et al. 1997).

A common practice in modern day cannabis production, based on our communications with Canadian medical cannabis producers and gray resources (Cervantes 2006), is to keep 2 to 3 leaves on each cutting and to remove about one-third of the leaf tips. The optimal leaf number on stem cuttings varies between species (Machida et al. 1977; Aminah et al. 1997; Alves et al. 2016), so species-specific evaluations are necessary.

The ability of stem cuttings to form adventitious roots often depends on the maturity of the stock plant. Cuttings from juvenile plants generally have improved rooting over those from mature plants (Altamura 1996). Juvenile plant material sometimes has a higher content of endogenous auxins and other rooting promoters compared with mature material (Husen and Pal 2006). This difference is evident in a number hardwood species such as oak (Morgan and McWilliams 1976), teak (Husen and Pal 2006), and American elm (Schreiber and Kawase 1975). Furthermore, in hardwood cuttings, maturity often varies by cutting position on the stock plant; stems from more basal regions often retain juvenile characteristics and have improved capacity to form adventitious roots (Hackett 1970). There is limited information and mixed findings on the effects of cutting position on adventitious rooting in softwood and herbaceous plants. In Schefflera arboricola (Hayata) Merr., softwood cuttings from more basal regions had lower rooting success rate and number of roots compared with those from apical regions (Hansen 1986), while in fever tea (L. javanica), cutting position had no effect on rooting success (Soundy et al. 2008).

It is well documented that treating the basal portions of stem cuttings in synthetic auxins such as indole-3-butyric acid (IBA) can improve rooting success rate, increase the speed of rooting, and increase the quantity of adventitious roots (Hartmann et al. 2002). In organic production, synthetic auxins such as IBA are often not permitted; thus, alternatives hormones or techniques are used to improve rooting success rate and quality. Willow (Salix alba L.) shoot extract is a naturally derived alternative to synthetic auxins and has been used successfully as a natural rooting hormone for mung bean [Vigna radiata (L.) Wilczek] cuttings (Arena et al. 1997) but had no effect on olive (Olea europaea L.) cuttings (Al-Amad and Qrunfleh 2016) or willow (Kawase 1964) cuttings. Currently, there is no peer-reviewed literature on any of the factors described above on cannabis.

The objective of the present study was to evaluate the influence of the following factors and their interactive effects on the propagation of stem cuttings in cannabis: (i) number of leaves, (ii) leaf tip removal, (iii) basal/apical position of stem cutting, and (iv) type of rooting hormone.

Materials and Methods

Stock plant conditions

Stock (mother) plants were maintained under an 18 h photoperiod with a mean canopy-level light intensity of 105 μmol m −2 s −1 (±61.2 μmol m −2 s −1 ) using ceramic metal halide 3100K lamps (Philips Lighting, Markham, ON). Temperature (day/night) was maintained at 20 °C (±0.03 °C), air relative humidity (RH; day/night) was maintained at 63% (±2.3%), and carbon dioxide (CO2) concentration (day/night) was maintained at 646 ppm (±59.7 ppm).

Stock plants were potted in 12.5 L air pruning pots (306 mm diameter × 275 mm height; Caledonian Tree Company Ltd., Pathhead, UK) containing a custom-blended organic growing substrate (60% sphagnum peatmoss and 40% bulk coconut coir; Premier Tech, Rivière-du-Loup, QC). The stock plants were 10 mo old and had between 20 and 25 nodes on their main stems. The plants were fertigated as needed using Nutri Plus Organic Grow liquid organic fertilizer [4.0–1.3–1.7 (N–P–K); Nutri Plus; EZ-GRO Inc., Kingston, ON] at a rate of 68 mg N L −1 amended with 2 mL L −1 of Ca–Mg supplement [3.0–1.6 (Ca–Mg); EZ-GRO Inc.] and 22.9 mg N L −1 of Organa ADD micronutrient supplement (2.0 N; EZ-GRO Inc.), with a 20% leaching fraction. Other nutrient element concentrations in Organa ADD were (in mg L −1 ): 100.0 Ca, 29 851 Zn, 4892 Mn, 1239 B, 12.7 Mo, 2419 Cu, and 2917 Fe.

Plant culture and treatments

Cannabis [Cannabis sativa L. ‘WP:Med (Wappa)’] cuttings were taken at a length of ≈13 cm and with three fully expanded leaves from stock plants. Cuttings were taken from the ends of axial limbs and cut at a 45° angle. Each cutting was rooted in a 5.7-cm-wide, 5.7-cm-tall peat-based pot (Jiffy Products N.B. Ltd., NB) containing Pro-Mix PG Organic growing substrate (Premier Tech) and arranged in trays at a density of 266 plants m −2 . The substrate was soaked in a solution of ‘Spurt’ liquid organic fertilizer [2.0–0.0–0.83 (N–P–K); EZ-GRO Inc.] at a rate that supplied 123 mg N L −1 .

The experiment was a full factorial completely randomized design with four factors (rooting hormone, leaf number, cutting position, and leaf tip removal), two levels per factor, and 10 replications per factor combination. For leaf number, cuttings had either one fully expanded leaf removed (two leaves remaining) or were left with three leaves. For cutting position, cuttings from terminal shoots were taken from either an apical position (node 10 and higher) or a basal position (below node 10). For the leaf tip removal treatment, a portion of the leaf tip (approximately one-third of the leaf area) was removed from the fully expanded leaves or the leaves were left uncut. For the rooting hormone factor, the base (≈5 cm) of each stem was dipped in either 0.2% IBA gel (synthetic rooting hormone; EZ-GRO Inc.) or in a 0.2% willow extract rooting gel (organic rooting hormone; EZ-GRO Inc.).

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Propagation environment

Trays were randomly arranged in a walk-in growth chamber (Conviron ATC60; Controlled Environments Ltd., Winnipeg, MB) and cuttings were misted with reverse osmosis water once, when they were placed in the chamber. From days 0 to 4 after cuttings were placed in the substrate (DAP), RH was maintained at 95% (±1.3%), reduced to 80% (±1.3%) for 5–8 DAP, and to 60% (±1.5%) for 9–12 DAP. Temperature was maintained at 24 °C (±0.04 °C) (day/night) for the entire period. Fluorescent lighting (Philips Lighting) was used to maintain an 18 h photoperiod. Photosynthetically active radiation at the canopy level was maintained at 50 μmol m −2 s −1 (±0.6 μmol m −2 s −1 ) for 0–4 DAP, 80 μmol m −2 s −1 (±0.7 μmol m −2 s −1 ) for 5–8 DAP, and 115 μmol m −2 s −1 (±0.5 μmol m −2 s −1 ) for 9–12 DAP.

Rooting assessment and harvest

The bottom of the trays were checked daily from 7 DAP onwards for protruding roots, and cuttings were harvested at 12 DAP when approximately more than 50% of the cuttings showed visible roots at the bottom of the tray. Rooting success rate was measured on a binomial scale in which any visible adventitious root formation was considered rooted. Rooting success was calculated as the percentage of cuttings with roots in each treatment. Successfully rooted cuttings were assigned to either of two classifications based on degree of adventitious rooting; a root quality index (RQI) score of ‘1’ or ‘2’ was assigned by a third party without knowledge of the applied treatments based on a visual reference (Fig. 1). Before RQI measurements, the substrate was washed from rooted cuttings with reverse osmosis water.

Statistical analysis

Data were analyzed using JMP Statistical Discovery Version 13.0 (SAS Institute Inc., Cary, NC) at a Type 1 error rate of ≤0.05. Rooting success rate and RQI data were analysed assuming a binomial error distribution using a generalized linear model and logit link function. Stepwise regression with a minimum small-sample-size corrected Akaike’s information criterion was used to remove non-significant interactive effects. Chi-squared contrasts were used to compare treatment means and interactive effects between treatments.

Results

Cuttings under all treatment combinations had some degree of successful rooting. Rooting hormone had the greatest effect on both rooting success rate and root quality (Figs. 2, 3). The synthetic hormone delivered a 2.1× higher rooting success rate (84% vs. 40%; χ 2 = 39.0, p < 0.0001) and 1.6× higher root quality (1.6 vs. 1.0; χ 2 = 41.1, p < 0.0001) than the organic hormone. Removing leaf tips had the second greatest effect on rooting success rate. When leaf tips were removed, rooting success rate was lowered from 71% to 53% (χ 2 = 9.8, p = 0.0018), although there was no effect on root quality. Leaf number had no effect on rooting success rate, but rooted cuttings with three leaves had 15% higher root quality than those with two (1.5 vs. 1.3; χ 2 = 4.3, p = 0.038). Position of the cutting did not influence rooting success rate or root quality. There was however, an interactive effect between cutting position and leaf tip removal on rooting success rate (Fig. 4). When leaf tips were removed, cuttings of basal origin had a lower rooting success rate than apical cuttings (43% vs. 63%; χ 2 = 5.7, p = 0.0169).

Fig. 2 . Rooting success rate of cannabis cuttings (means ± standard error of the mean; n = 80). Cut leaves had about 30% of leaf tips removed. Cuttings were from terminal shoots, with apical cuttings taken from ≥ node 10 and basal cuttings from < node 10. The synthetic rooting hormone was a 0.2% indole-3-butyric (IBA) acid gel and the organic was a 0.2% willow extract gel. Bars within each factor (e.g., leaf number) bearing different letters are significantly different at p < 0.05 using χ 2 contrasts.

Fig. 3 . Root quality index of cannabis cuttings (means ± standard error of the mean; n = 80). Cut leaves had about 30% of leaf tips removed. Cuttings were from terminal shoots, with apical cuttings taken from ≥ node 10 and basal cuttings from < node 10. The synthetic rooting hormone was a 0.2% indole-3-butyric (IBA) acid gel and the organic was a 0.2% willow extract gel. Bars within each factor (e.g., leaf number) bearing different letters are significantly different at p < 0.05 using χ 2 contrasts.

Fig. 4 . Rooting success rate of cannabis cuttings (means ± standard error of the mean; n = 40). Cut leaves had about 30% of leaf tips removed. Cuttings were from terminal shoots, with apical cuttings taken from ≥ node 10 and basal cuttings from < node 10. Treatments with different letters are significantly different at p < 0.05 using χ 2 contrasts.

Discussion

Rooting hormone

The use of IBA led to a markedly higher rooting success rate and greater root quality than the organic hormone. Similar success with IBA has been documented in other species propagated by stem cuttings (Al-Saqri and Alderson 1996; Saffari and Saffari 2012). In studies on the effects of centrifuged willow shoot extracts on willow and mung bean stem cuttings, willow extract application increased adventitious rooting in mung bean but had no effect in willow cuttings (Kawase 1964, 1970). The authors attributed the improved rooting in mung bean to a synergistic effect between indole-3-acetic acid (IAA) in the cuttings and two unknown root-promoting fractions identified in willow extract. This synergistic effect was explored in adventitious rooting in bean cuttings in Gesto et al. (1977) and was attributed to the presence of the compound catechol in willow extract. Kawase (1970) suggested that only cuttings with sufficient IAA, such as mung bean, would see improved rooting from the synergism. A recent evaluation on the effects of willow extract on olive stem cuttings (Al-Amad and Qrunfleh 2016) showed that, similar to willow cuttings, willow extract had no effect on adventitious rooting in olive cuttings. The relatively poor rooting success rate of cannabis cuttings treated with willow extract in the present study could be attributed to a lack of IAA in the cuttings. Further study is required to measure IAA in cannabis cuttings and to further explore the synergistic effect between IAA and catechol on adventitious rooting. Also, more organic rooting hormones need to be explored and evaluated for cannabis propagation to provide alternatives for growers that choose organic production.

Leaf number/leaf tip removal

Rooting success was similar between cuttings with two and three leaves, suggesting that two leaves may provide sufficient carbohydrates, auxin, and rooting co-factors (Haissig 1974) for successful rooting in cannabis. In the propagation of stem cuttings, increased photosynthetic surface area and resultant carbohydrate supply generally increased rooting success rate until another factor such as evapotranspiration stress became limiting (Davis and Potter 1989). Cuttings with three leaves showed no signs of wilting or other indications of evapotranspiration stress. It is likely that both two- and three-leaf treatments exhibited little evapotranspiration-induced water stress in the stable high humidity provided in this trial. It is estimated that under conditions of lower or less stable humidity, fewer leaves would deliver an improved rooting success rate as these cutting would have a lower evaporative demand from humidity.

Notably, three leaves increased root quality over two. The observed quality improvement was likely caused by the additional carbohydrates, rooting co-factors, endogenous auxin (Haissig 1974), or a combination of these factors provided by the additional foliage. Further study is required to evaluate the effect of each of these factors and their interactions on cannabis stem cuttings to discern their relative importance. Based on this finding, it is recommended that cannabis cuttings be taken with three or potentially more leaves (to improve rooting quality) so long as humidity during propagation can be adequately maintained.

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It was expected that cutting leaf tips would have a similar effect to reducing leaf number because the source and thus potentially the amount of photosynthetic material was manipulated; however, cutting leaf tips reduced rooting success and had no effect on rooting quality.

Both cutting leaf tips and leaf number altered the surface area for evapotranspiration and photosynthesis; however, there was a notable difference in the effects of these treatments. Leaf cutting influenced rooting success rate while leaf number influenced root quality. Further study is necessary to discern the reason for these differing effects. Based on these findings, it is recommended that leaf tips not be cut in cannabis cuttings; and, if less leaf material is desired to conserve space in the propagation environment or to prevent evapotranspiration stress, then fewer whole leaves be used instead.

Cutting position

There was no indication that basal cuttings had improved rooting success rate or quality over apical cuttings. Similar results were found in stem cuttings of fever tea (Soundy et al. 2008) and may be attributed to the lack of distinct stages of maturation in these herbaceous plants in contrast to most hardwood species (Schreiber and Kawase 1975; Morgan and McWilliams 1976; Husen and Pal 2006). These findings suggested that in cannabis, cutting position does not play an important role in rooting.

Interactive effects

There was an interactive effect between leaf tip removal and cutting position. Cuttings from basal positions with two leaves had lower rooting success rate than any other combination of these two factors. In general, basal cuttings had smaller leaves (general observation without measurement) than apical cuttings, which, through the cutting of leaf tips, were left with less overall leaf surface area. The reduction in photosynthesis resulting from the smaller leaf area might have then resulted in the lower rooting success rate.

Conclusions

Type of rooting hormone strongly influenced the success and quality of adventitious rooting in cannabis cuttings, with the 0.2% IBA gel delivering a higher rooting success rate than the 0.2% willow extract. Removing 30% of leaf tips from cuttings reduced rooting success rate and three leaves had higher root quality compared with two leaves without influencing rooting success rate. Position of cutting on the stock plant did not influence either rooting success rate or root quality. To achieve maximum rooting success and root quality, cuttings from either apical or basal positions should have at least three fully expanded uncut leaves and be dipped in an IBA rooting hormone. If a reduction in leaf area is desired, either because high humidity cannot be maintained or more airflow is desired in the propagation environment, then lowering the leaf number to two fully expanded leaves is preferential to cutting leaf tips.

Acknowledgements

We thank ABcann Medicinals Inc. for providing funding as well as materials, expertise, and ground-level support. We also thank EZ-GRO Inc. for providing materials and technical support, as well as T. Graham for his advice on trial planning and data analysis.

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