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11 Flax (Linum usitatissimum L.) and Hemp (Cannabis sativa L.)... 203

crop provides 100 % utilisable raw material with fully biodegradable waste and no
harmful residues.

11.3 Hemp (Cannabis sativa L.): Botanical Characterisation
and Economical Uses

The exact origin of Cannabis is unclear, because it was dispersed across Eurasia by
humans very early in pre-history. However, Central Asia offers by far the most
plausible location for the origin of Cannabis. From Central Asia Cannabis was
carried out throughout East Asia, South Asia and Europe which served as primary
centres of domestication and secondary gene pools (Clarke 1999). Recently, Can-
nabis is dispersed and grown throughout the world from subarctic to tropical
regions. China has produced the oldest archaeological and historical evidence
(around 2700 BC)of Cannabis cultivation and use (Ranalli and Venturi 2004). It
is likely that the Chinese were the first to use wild Cannabis and domesticate it for
its fibre and seed, and that Indians were the first to use it and domesticate it for its
psychoactive properties (Abel 1980; Clarke 1999).
Cannabis and Humulus are the only genera in the family Cannabaceae. There
are several taxonomic views on the genus Cannabis—the most common ones
consider genus Cannabis as monospecific, i.e. C. sativa with two subspecies
(Small and Cronquist 1976) or split Cannabis into three species C. sativa, C. indica
and C. ruderalis (Schultes et al. 1974), with the last-mentioned species to be a truly
wild taxon and probable ancestor to cultivated hemp varieties (Clarke 1999).
Recent application of biochemical (Hillig 2005) and molecular markers (Faeti
et al. 1996; Kojoma et al. 2002; Mandolino and Ranalli 2002; Gilmore and
Peakall 2003) for Cannabis germplasm evaluation promises to bring new light
into Cannabis phylogeny and taxonomy.
Cannabis is a medium to tall, erect, annual herb. However, environmental
influences on the growth habit of Cannabis are very strong. Provided with an
open sunny environment, light well-drained soil, and ample nutrients and water,
Cannabis can grow to a height of 5 m in a 4- to 6-month growing season (Clarke
1999), thus forming a huge above-ground biomass (Table 11.1). In contrast, when
growing in arid locations with limited soil nutrients, Cannabis plants develop
minimal foliage and may mature and bear seed when only 20 cm tall. Plant density
in a square unit affects significantly plant architecture—when planted in close
2
stands (for fibre production; ca. 100 plants per m ), hemp plants do not branch
but grow as tall, thin, straight stalks. When grown for seed production (ca. 4 plants
2
per m ), hemp plants are extensively branched. Cannabis is normally a dioecious
plant (male and female flowers develop on separate plants), although monoecious
individuals with flowers of both sexes on one plant are occasionally found. Before
flowering, the sexes of Cannabis are indistinguishable, except for general trends in
growth habit in certain strains as height and extent of branching. Cannabis is