Zanthoxylum piperitum, commonly known as Japanese pepper, Sansho pepper, or prickly ash, is a small deciduous tree or shrub that can grow up to 5 meters in height. It is native to Japan, Korea, China, and Taiwan, and is commonly cultivated in other parts of Asia as well as in North America and Europe. Its leaves are green, glossy, and have a citrusy aroma. The fruit of the plant is a small, reddish-brown berry-like drupe that has a sharp, pungent, and citrusy flavor. The seeds inside the fruit are also used as a spice. It is a temperate species that is unlikely to become naturalized or invasive in the Hawaiian Islands but may be able to spread by its bird-dispersed seeds if grown in cooler, higher elevation habitats. Its spines may also deter browsing by feral ungulates, giving it a competitive advantage over other unarmed, or palatable vegetation.
High Risk Traits:
- Prickles or spines on branches at base of leaves
- Reported to be unpalatable to deer in native range (although deer may browse on young growth)
- Reported to be tolerant of deep shade (and could potentially invade intact forest understory)
- Tolerates many soil types.
- Reproduces by seeds and potentially by suckering.
- Seeds dispersed by birds, other frugivorous animals, and through intentional cultivation.
- Seeds may form a persistent seed bank.
- Tolerates pruning and may resprout after cutting if mechanical control is attempted.
Low Risk Traits:
- No reports of naturalization or invasiveness where introduced.
- A temperate species that may only pose a risk of naturalization or invasion in cooler, higher elevations of tropical islands.
- Reaches maturity in 3+ years.