Effect of Sowing Date on Growth and Development of Thai Hemp (Cannabis sativa L.)

Abstract

A field trial of Thai hemp was conducted at the Queen Sirikit Botanic Garden, Chiang Mai province, northern Thailand, with plantings at a density of 25 plants m^-2 during July, August, September and October 2004 to determine the effect of sowing date on hemp growth and development. The flowering time of all treatments started in October the same year. Plant height declined (205, 180, 130 and 95 cm) and diameter declined (11.95, 8.17, 8.00 and 3.90 mm) from the earliest planting date, respectively. An earlier sowing date allowed a longer vegetative period, which in turn produced a longer stem. The commencement of flowering was a factor that ended plant height growth. Late planting reduced stem length and the time when plants ended their growth, with less time needed to change from the vegetative to the reproductive phase for the late planting. Phyllotaxis changed from 5.86 to 6.33 leaf pairs. The ratio of male to female plants was 57.68: 42.32. The results also indicated that the planting time for hemp in Thailand should be before July and August, to produce appropriate growth and development.