The difference between spring wood and summer wood, referred to as earlywood and latewood respectively, varies among species but is characterized by different densities and growth ring sizes. In many temperate softwoods, there is a clear difference between spring and summer wood growth patterns. In other varieties, namely the diffuse-porous woods, there is little difference between the early and late woods.
In temperate softwoods, spring wood is much lighter in color and weight than summer wood. These differences are apparent when the woods are compared by the naked eye but are more pronounced at the microscopic level. When examined by a microscope, cells of dense latewood are more compact than those in spring woods. Additionally, cells in summer wood have stronger and thicker walls and small cell cavities. Spring woods of temperate species, in contrast, have large cell cavities and thin cell walls. The thinner spring wood appears as a smaller ring and is generally softer and more flexible. This difference is pronounced in pines and walnut trees; their rings formed in spring are much lighter and thinner, appearing as soft amber in color, while summer woods are darker and appear like maple syrup. Trees with porous woods display little difference between spring and summer growth, as their pores distribute water evenly throughout the wood and their growth rates remain constant from spring through summer.