Forest restoration research in northern Thailand, 1. The fruits, seeds and seedlings of Hovenia dulcis Thunb. (Rhamnaceae)

Hovenia dulcis Thunb. (Rhamnaceae) is a rare native tree species recently added to Thailand's flora, found in stream valleys in primary lower montane evergreen forest 1,075- 1,250 m above sea level. It is a deciduous tree, shedding its leaves from late August to February. It flowers from December to May and fruits from August to January. Seeds begin to germinate 17-77 days after sowing and continue to do so over several months. A detailed description of the seedling is presented. Due to the rarity of this species, we recommend including it in tree planting programs for forest restoration to prevent its local extinction and to increase the diversity of regenerating forests. To produce seedlings, collect seeds in November-January and planted in nurseries under moderate shade (about 40% full sunlight) in forest soil with high organic matter content. The seeds and seedlings should be kept well watered and protected from animals. Under favourable conditions， seedlings should reach a size suitable for planting in less than 12 months. Stream valleys in degraded evergreen forest at 1,000-1,300 m above sea level are the most promising planting sites for this species, but experiments at other sites are recommended.