William Penn Barberry comes with a provenance: it was introduced by the Henry Foundation of Gladwyne, Pennsylvania, a crossbred selection from B. verruculosa and B. gagnepainii that has proven itself as a garden-worthy evergreen shrub in the three to five foot range. The glossy green leaves carry an appealing seasonal honesty, turning a rich red-bronze in autumn before the winter sets in, while clusters of small yellow flowers open reliably in early spring.

As a practical garden plant, it covers multiple needs at once. The spiny stems make it genuinely effective as a privacy screen or a deterrent to unwanted foot traffic, a role that requires no additional persuasion from the gardener. It tolerates drought once settled in and resists deer firmly. One caveat worth noting: in areas where winter temperatures drop to zero Fahrenheit, it will not survive, so hardiness zone 6 is a meaningful lower limit. Birds eat the red berries and spread the seeds, which means in some settings it can spread aggressively into thickets.