The crimson pygmy barberry (Berberis thunbergii 'Crimson Pygmy' or 'Atropurpurea nana') is a dwarf Japanese barberry shrub that grows to only 2 feet tall and 3 feet wide. This deciduous shrub is deer- and insect-resistant, with deep red foliage and a dense, compact growth habit. The crimson pygmy barberry grows best in USDA hardiness zones 4 through 8, tolerating winter temperatures down to minus 25 degrees Fahrenheit. The small shrub also produces bright red ornamental berries in fall when the foliage begins to turn orange-scarlet.
Plant your crimson pygmy barberry in full sunlight and in well-draining soil. Spread a 3- to 4-inch-thick layer of bark mulch on the ground around the base of the shrub to help retain soil moisture and control weeds.
Water your pygmy barberry once per week in the absence of rainfall to provide 1 to 2 inches of water each week. Water the shrub two to three times per week during extreme summer heat or droughts.
Feed your crimson pygmy barberry once each year in early spring, right before new growth emerges. Apply a slow-release, all-purpose fertilizer according to the instructions on the label.
Trim the barberry shrub in winter to keep it tidy. Remove all damaged, broken, crowded or crossing growth, and shear the shrub to shape it if desired.