The success of any forest restoration project depends on the provision of top quality planting stock. Therefore, FORRU has conducted numerous nursery experiments to develop horticultural practices that optimise seedling vigour and health (Blakesley et al., 2000). Germination trials were carried out on more than 400 native forest tree species (Blakesley et al., 2000). Some species germinated easily, whilst others proved difficult. So various treatments to break dormancy were tested, including scarification, heat treatments and soaking in water and acid (Kopachon, 1995; Singpetch, 2001;Vongkamjan, 2003). For those species that proved difficult to grow from seed, vegetative propagation from cuttings (Vongkamjan, 2003) and the nurturing of seedlings dug up from the forest (Kuarak, 2002) were also investigated. Above left: Scarifying Ormosia sumatrana seeds using nail clippers.

Experiments were then conducted to determine the best container types and media for seedling growth and survival (Zangkum, 1998;Jitlam, 2001). Various methods of fertilliser application and pruning were also tested.

Different tree species produce seeds at different times of the year and seedling growth rates also very among species, yet all species must grow big enough for plating by the beginning of the rainy season. Therefore, one of the main aims of research in the nursery was to identify treatment combinations that produce trees of a plantable size and quality by the first or second planting season after seed collection.

This led to the development of production schedules for many tree species, which can be used by nursery managers to formulate effective nursery production programmes for mixed crops of framework tree species (Kuarak et al., 2000; Elliott et al., 2002; Blakesley et al., 2000).

Currently research is focusing on rare tree species. The nursery and research staff initially spent a lot of time finding the rare trees within the National Park, and then conducted phenology studies to determine when seeds could be collected. The next step is to find treatments to germinate the seeds or find other ways to propagate these vulnerable species.

The main nursery at Doi Suthep-Pui National Park currently produces approximately 80,000 trees per year of around 200 species. As well as trees for experiments, the nursery provides trees to a host of other organizations, which results in substantial input of indigenous forest trees into planting projects throughout the north. Our nursery is unique in northern Thailand as we grow such a wide variety of native tree species. For FORRU's recent lowland forest restoration activities, we now have a small nursery which supplies the seedlings for planting.