Native species of the Dipterocarpaceae are being planted throughout Southeast Asia as a source of future timber and to restore degraded lands. A detailed understanding of factors controlling seedling performance is required for the successful planting of dipterocarps. Below-ground resource availability is hypothesized to have a significant affect on seedling performance of dipterocarp species when planted in selectively logged forests or in open, degraded areas. This study tested three methods thought to increase below-ground resource availability and thereby improve the performance of two dipterocarp species ( Dryobalanops aromatica and Shorea parvifolia) when grown in degraded secondary forest: nutrient addition, mulching, and increased planting-hole size. Seedlings of the two species were grown in two planting-hole sizes ( 12 cm×18 cm and 20 cm×30 cm), with and without nutrients (NPK), and with and without mulching. The experiment was conducted in two sites (Sampadi and Balai Ringin) in Sarawak, Malaysia, to test for spatial variation in treatment effects. Seedling growth and survival were monitored over 22 months. Seedling survival was >94% for both species and did not differ significantly among any of the treatments. High monthly rainfall throughout the first year of the experiment may have enhanced seedling survival. Nutrient addition had the strongest effect on seedling growth for both species, with nutrient addition increasing growth by >50% at Sampadi and for D. aromatica in one block at Balai Ringin. There was significant spatial variation in treatment effects. S. parvifolia did not respond to nutrient addition at Balai Ringin, suggesting that the plants may not have received the added nutrients in that site. Mulching had a positive effect on growth at Sampadi, but no effect or a negative effect at Balai Ringin. Further analysis of the specific effects of mulching on resource supply is required. Planting-hole size did not have a consistent significant effect on the growth of either species. This may have been due to the favorable soil water status during the experiment. The results of this experiment emphasize the potential importance of site effects and interactions between site and treatment effects in enrichment planting trials using dipterocarps. Further experimental studies on below-ground resource limitations of dipterocarp growth in a wide range of sites are required. Studies that monitor the availability and fluxes of soil resources will be the most informative.