Photo showing the tall flower spikes of acanthus mollis plants growing in a herbaceous border, as part of a landscaped garden. Acanthus is a particularly hardy and popular perennial plant, with large and prickly dark green leaves. The flowers are described as being tall racemes, made up of both white flowers and purple bracts. This plant is often referred to as 'Bear's breech' and belongs to the Acanthaceae family.