Conifer needles are a lot tougher than deciduous leaves and don't lose water as quickly, which means they can stay alive and green even in the winter. Not all trees with needles are pine trees. Minnesota's native evergreens include spruce and fir too. Look at the leaves. Pines have long, slender needles in groups of two to five.
Spruces have four-sided, short, stiff, and sharp single needles.
Firs have short, flat single needles. Sticky resin formerly used for mounting specimens on microscope slides, sealing birch bark, making varnishes. Deciduous trees such as oaks and maples lose their leaves in the fall. Scientists call these trees angiosperms. Angio comes from the Greek word for case.