Populations of forest trees and other native plants are genetically different from each other and adapted to different climatic conditions. As a result, natural resource managers must match the climatic adaptability of their plant materials to the climatic conditions of their planting sites. Typically this has been done by using geographically defined seed zones or seed-transfer rules that specify a geographic distance beyond which populations should not be moved. Past guidelines also assumed stable climates over the long-term, an assumption that is unlikely given projected climate change. Current climate interpolation models can now be used to specify zones or rules based on climate rather than geography. Seeing the need for a tool that could help managers, scientists, and policymakers plan for the effects of changing climates, Brad St.Clair, a research geneticist with the Forest Service’s Pacific Northwest Research Station, and his colleagues developed a web-based application called the Seedlot Selection Tool. Users can explore options for matching seedlots to planting sites based on current and predicted future climatic information. The tool allows managers to play with alternative scenarios, including those that respond to concerns about climate change using assisted migration. The Forest Service and other agencies have begun using the Seedlot Selection Tool to explore options for appropriate seedlots for reforestation. For example, in Oregon, the tool was used to determine that available plant material on the Ochoco National Forest was appropriate to plant at a site following a burn on the Malheur National Forest. The tool has also been used by researchers and managers to explore adaptation of native populations and options for assisted migration at sites in the Pacific Northwest; the Northeast; Alaska; and Ontario, Canada.