Acanthus mollis
Common Name: bear's breeches
Type: Herbaceous perennial
Family: Acanthaceae
Native Range: Southern Europe, northwestern Africa
Zone: 7 to 10
Height: 3.00 to 5.00 feet
Spread: 2.00 to 3.00 feet
Bloom Time: June to July
Bloom Description: White (sometimes pink)
Sun: Full sun to part shade
Water: Medium
Maintenance: Medium
Flower: Showy
Other: Thorns

Culture

Winter hardy to USDA Zones 7-10 where it is easily grown in average, fertile, medium moisture, well-drained soils in full sun to part shade. Plants tolerate a wide range of soils except poorly-drained ones. Plants may not flower well in too much shade. Late spring frosts can impair or eliminate flowering for the year. Remove flowering stalks after bloom. In cold winter areas, plant foliage should be left in place over winter but removed in early spring as new foliage appears. Plants can spread aggressively by creeping rootstocks, particularly in loose soils. Unwanted spread can be addressed by root barriers. Plants generally spread less in the northern parts of their growing range. Plants are best propagated from root cuttings taken in early spring, but may be grown from seed. Plants can be slow to establish in the garden (particularly if started from seed), but become somewhat difficult to eradicate once established since small sections of root left behind can sprout new plants. This plant is not reliably winter hardy to the St. Louis area. If attempted in St. Louis, it should be sited in a protected location and mulched.

Noteworthy Characteristics

Acanthus mollis, commonly known as bear’s breeches, is a clump-forming perennial that is grown as much for its attractive foliage as for its architecturally bold flower spikes. It is native to the Mediterranean region. Creamy white (sometimes pink) snapdragon-like flowers, each hooded and subtended by spiny reddish-purple bracts, bloom in late spring to midsummer in vertical rows on substantial flower spikes that rise well above the foliage mound to 3-5’ tall. Deeply lobed, soft-spiny, glossy, dark green leaves (to 2’ long) form a mound of basal foliage. Foliage is mostly evergreen in warm winter climates, but plants lose their leaves when winter temperatures dip below 20 degrees F.

Acanthus leaves have a classical appearance and were the source of the Corinthian leaf motif developed and used as a decoration in ancient Greek and Roman art and architecture. It is believed that the leaves of A. mollis or A. spinosis were the model for the sculptured leaves that adorn the capitals of the Corinthian columns that became popular in the 4th century B.C.

Problems

No serious insect or disease problems. Snails and slugs are occasional visitors that can do substantial damage if left unchecked. Plants can spread aggressively in optimum conditions.

Garden Uses

Bold, stately plants that may be grown as specimens but are perhaps best in small groupings. Borders or formal gardens. For the St. Louis area, A. spinosus is a similar plant with better winter hardiness.