Pepperbark, toothache tree, tickle tongue, and prickly ash are among the many common names given to the deciduous temperate tree also called Hercules-club (Zanthoxylum clava-herculis). This native tree was planted at the Oslo Riverfront Conservation Area (ORCA) in 2001 as part of a demonstration planting in a disturbed area. You will find it thriving and reproducing where it was planted on the north side of the main trail near the culvert crossing.
Likely you will need to look up to spot them. Hercules-club trees can grow to be 50′ tall, especially in shady conditions as at ORCA. They grow quite quickly in full sun, and, when they are young, it is easy to understand the common name Hercules-club from their vicious looking bark …
With time the spines and armor wear away …
Hercules-club has pinnately compound leaves with significant spines along its rachis (leafstems) that are reddish in color. The tops of its leaflets are dark green, and the underside is lighter green. Hold a leaf up to the light to see its pellucid dots (a.k.a. translucent dots).
Plants in the citrus family, Rutaceae, and in the myrtle family, Myrtaceae, often have pellucid dots, Hercules-club is part of the citrus family, and its pellucid dots contain aromatic “citrusy” oils. If you chew on a leaf, these aromatic oils will numb your mouth and impart a lemony flavor. That is why this plant is sometimes called the toothache tree.
Terminal multi-stemmed clusters (racemes) of tiny yellow-green flowers come in the early spring. The flowers are significant nectar and pollen source for European honeybees (Apis mellifiera) and other pollinators.
In the late spring or early summer, fruits begin to form in capsules that ripen from green to tan …
Each capsule contains a single glossy black seed. Birds consume and spread the seeds.
The capsule valves of other species of Zanthoxylum are used as a spice in China, India, Korea, Indonesia, Africa, and other countries. According to a recent article titled Florida Szechuan Pepper: A Financial Opporuntity, in the Palmetto, the quarterly journal of the Florida Native Plant Society, Hercules-club valve capsules have a “pungent lemony flavor” that “was soon overwhelmed by a remarkably strong numbing of tongue and lips”.
Properly placed, hercules-club — with its thorns and pellucid dots — can be a great addition to your landscape for birds, pollinators, and “spice”. Like commercial citrus, it is a larval host plant for giant swallowtail butterfly (Papilio cresphontes).
Enjoy the Oslo Riverfront Conservation Area 