Berberis thunbergii, commonly known as the Japanese barberry, is a dense, deciduous shrub that typically reaches about 3 to 6 feet in height with a similar spread of roughly 4 to 7 feet, forming a rounded to slightly arching habit. Individual stems are slender and can extend 2 to 4 feet long, often bearing sharp single spines approximately 0.25 to 0.5 inches in length at each node. The small, oval leaves measure about 0.5 to 1.25 inches long and 0.25 to 0.75 inches wide, appearing in clusters along the stems and turning vibrant shades of red or orange in fall. In spring, pale yellow flowers about 0.25 to 0.4 inches across hang in small clusters 0.5 to 1 inch long, later developing into bright red, oblong berries measuring roughly 0.3 to 0.5 inches long that persist into winter. The root system is relatively shallow but wide-spreading, often extending outward as much as the plant’s canopy width, contributing to its ability to form dense thickets over time.