Growth characteristics of Cannabis sativa L. cultivated in a phytotron and in the field.
Growth characteristics of Cannabis saliva L. are indispensable factors to verify the statements by the criminals of illegal cannabis cultivation. To investigate growth characteristics of C. sativa, two varieties, cannabidiolic acid (CBDA)-rich (CBDA-type) which being cultivated for fiber production and delta9-tetrahydrocannabinolic acid (THCA)-rich (THCA-type) which is used for drug abuse, were cultivated from seeds under the same growth environment in a phytotron. THCA-type showed high germination rate (100%) whereas only 39% of the CBDA-type seeds germinated 6 days after sowing. Plant height, number of true leaves, number of nodes, number of axillary buds and flowering of these two varieties were periodically observed. THCA-type grew more rapidly (plant height: 125.8 cm for THCA-type, 84.7 cm for CBDA-type, 75 days after cultivation) demonstrating vigorous axillary bud formation and earlier male-flowering (63 days for THCA-type, 106 days for CBDA-type, after sowing). Propagation of THCA-type was tested using the axillary shoot cuttings of female plants either with or without the main stem. All the cuttings with the main stem rooted after 21 days and grew healthily in a phytotron. However, all the newly developed leaves were single instead of palmate. In the field, THCA-type male-flowered after 155 days of cultivation after sowing on March 31. The height of the field-cultivated plants reached 260.9 cm 163 days after sowing. Despite the great differences in final plant heights, the increases of plant height per day during the vegetative growth stage were similar in the field and in the phytotron. Thus estimating the starting time of illegal cannabis cultivation might be possible if the plant is in the vegetative growth stage.