- Deciduous shrub, (similar to the species), 3-6 ft (0.9-1.8 m), very dense, rounded form, thorny, foliage is reddish or purplish in summer and red in fall.
- Full sun needed to develop color. Not fussy, but prefers acid or neutral soil.
- Hardy to USDA Zone 4 Originated in France in about 1913. Vegetatively and seed propagated.
Many cultivars have been selected from this form (var. atropurpurea), including:
- ‘Bagatelle’ - dwarf, more compact and smaller leaves than ‘Crimson Pigmy’.
- Cherry Bomb® (‘Monobm’) - color similar to ‘Crimson Pigmy’, but more open branching, slow growing to 3-4 ft (0.9-1.2 m) tall and wide.
- ‘Crimson Pigmy’ - dwarf, reddish purple foliage, low growing, about 2 ft tall and 3 ft wide (0.6 × 0.9 m).
- ‘Golden Ring’ - reddish purple leaves with a yellow-green border around the margin, only noticeable when viewed close-up.
- ‘Red Chief’ - glossy purple leaves in late spring, become greenish purple when mature and a bright orange-purple in fall.
- ‘Rose Glow’ - new foliage is rose-pink, mottled with deeper red-purple splotches, matures to a deep reddish purple.
- Royal Burgundy™ - dwarf, rounded form, deep burgundy foliage becoming black-red in fall.
Name calling? A lack of taxonomic uniformity:
Some authorities classify the red/purple leafed group as a taxonomic subdivision of the species (Berberis thunbergii), specifically as a variety, varietas, (var.), hence as Berberis thunbergii var. atropurpurea (atropurpurea = dark purple).
Other authorities us the term forma (f.), this term is used to recognize and describe sporadic variations in a species, in this case Berberis thunbergii f. atropurpurea.
- A taxonomic authority (ITIS) lists the name Berberis thunbergii var. atropurpurea as “not accepted” and a synonym of the species, Berberis thunbergii. In other words atropurpurea is not a taxonomic rank so that a red/purple leafed plant might be designated as a selection, hence Berberis thunbergii ‘Atropurpurea’. This is how many nurseries name the red/purple leaved selections, e.g., B. t. ‘Atropurpurea', B. t. ‘Crimson Pigmy’, etc.