This week for Flora and Fauna Friday it’s a curious coastal shrub that’s as good at inflicting pain as it is at killing pain, Southern Prickly-Ash (Zanthoxylum clava-herculis).
Southern Prickly-Ash is a small tree in the citrus family found scattered across the coast of the Southeast United States. Here in South Carolina, it’s limited to the Lowcountry and primarily to barrier islands and Sea Islands, like Edisto. It’s a common sight on beaches and in sandy forest edges further inland. Southern Prickly-Ash has a gnarled growth, pale-gray bark, leathery emerald-green compound leaves, and is covered in corky protrusions and prickles. It generally grows about ten to twenty feet tall with multiple stems. Southern Prickly-Ash goes by many names including, Toothache Bush and Hercules’ Club, and each alludes to a different characteristic. The name Hercules’ Club references the trunk of the plant. The club of the Greek hero Hercules is often depicted as being covered nodules or conical points and indeed our plant is covered in pointy conical nodules all along its stem. Southern Prickly-Ash tells us the plant is found in the south, it’s prickly, and it resembles an Ash tree. Conveniently, it is all three. Both the stems and the trunk of Southern Prickly-Ash are all covered in vicious woody prickles and the prickles on the trunk eventually transition with age into corky pyramids. (Prickles is the technical term here, as these pointy bits are grown out of the plants’ bark. Thorns grow out of the wood of the stem and spines are modified leaves.) Also, its leaves do in fact look a bit like an Ash, with a pinnately compound leaf usually holding seven to nine leaflets. However, the most intriguing name is Toothache Bush. The leaves of Southern Prickly-Ash are glossy with a burgundy rachis down the center studded by prickles between the leaflets. They are also thick and leathery. As these plants often grow in stressful habitats with poor soils and these leaves take a good deal of work to grow, they strongly prefer if critters don’t make their lives any harder by eating their leaves. To this end, they have covered themselves in prickles and have also invested in chemical warfare. The flesh of Southern Prickly-Ash contains chemicals designed to repel and incapacitate insect pests. One of those chemicals is spilanthol, which kills insects but can work as a local anesthetic in humans. Traditionally, Native Americans often used it to treat toothaches, as chewing on the twigs or leaves of Southern Prickly-Ash will numb the mouth and tongue with a tingling sensation that allows you to ignore mouth pain. However, this chemical warfare isn’t perfect and I know of one species of insect that has learned to tolerate it, the Giant Swallowtail. The Giant Swallowtail is our largest species of butterfly in the South Carolina and its native host plant is Southern Prickly-Ash. Southern Prickly-Ash is also important to other wildlife. It blooms in mid-spring with cluster of tiny green flowers utilized by pollinators and produces small black berries eaten birds.
