Scientists conducted a four-year study on two recently harvested forest sites in western Washington and Oregon to determine how logging debris and competing vegetation interacted to affect growth of planted Douglas fir seedlings. They found stem growth of seedlings with 40 percent debris cover and competing vegetation was greater than that of seedlings with zero or 80 percent debris covers because the intermediate cover of debris both reduced herb abundance and increased availability of soil water and nitrogen. Where competing vegetation was removed, seedling growth was greatest with 80 percent debris cover because it reduced soil temperature and evaporation, resulting in greater availability of soil water and nutrients. Forest managers of Green Diamond Resource Company and Port Blakely Tree Farms, LLC, are using the information to justify retention of moderate levels of logging debris in combination with herbicide treatments to provide short-term control of competing vegetation and increased growth of planted conifers. Washington State's Department of Natural Resources is using this information regarding the benefits of retaining logging debris on low nutrient sites to aid forest regeneration to inform planning for biomass energy harvesting, animal damage control, and wildfire hazard reduction.