Staminate and pistillate flowers occur on separate plants as catkins. The fruit is a narrowly ovoid capsule. Sandbar willow is able to reproduce vegetatively by sprouting from underground shoot buds which occur on lateral roots and produce male or female clones. Regeneration may also occur through broken pieces of stems and roots which are transported and deposited by floodwaters and later sprout.
Reproduction occurs sexually through the production of numerous seeds.
The nondormant seeds have a thin seed coat and germinate soon after being dispersed. Fresh alluvium deposited along rivers provides an ideal substrate for establishment. It characteristically forms zones immediately adjacent to the water's edge. These areas are subjected to periodic flooding which often deposits sand and cobble below the high water mark. It normally does not exist in the understory due to its shade intolerance, and is generally replaced by cottonwoods.