Thursday, January 26, 2017

February Plant of the Month – Hercules Club (tree)

February Plant of the Month – Hercules Club (tree)

Hercules Club
Zanthoxylum clava-herculis l.
Other Names: Pepperbark, Toothache Tree, Tickle-tongue, Prickly Ash
Family: Rutaceae (Rue or Citrus Family)
Synonym: Zanthoxylum macrophyllum

Larval host for the Giant Swallowtail Butterfly

By Sharon and David Parrish

Imagine, if you will, Hercules, the mythological son of Zeus with the strength of a lion searching through Texas to find a tree for his legendary club. Surely, he would be drawn to the Zanthoxylum clava-herculis or Hercules Club with its distinctive knobby warts along the trunk. Today he could find two small specimens in the Butterfly Garden at Hagerman National Wildlife Refuge. In addition, Dr.Wayne Meyer reports that several examples can easily be seen along Meadow Pond Trail. 

(Photo by Richard Murphy, licensed under the Creative Commons)

Medicine: Also known as the toothache tree or tickle-tongue, the Native Americans and the early European settlers were known to chew the leaves and the bark to soothe a throbbing tooth. The major active compound is chelerythrine. This benzophenanthridine alkaloid exhibits anti-bacterial activity against the common, infectious microbe, Staphylococcus aureus (i.e., the staph infection). This highlights the importance of protecting our planet’s extensive botanical treasures, which harbor cures to countless human ailments. “As of 2003, at least 25 percent of modern medicines were derived from plants, yet only a tiny fraction of the estimated more than 50,000 medicinal plants used around the globe have been studied in the lab.” 5

Identification: Z. clava-herculis is a small, round-headed tree with smooth gray bark covered by triangular-shaped knobby prickles on the bark; thorns emerge from these triangular bumps when the plant is young, then as the plant ages and the “triangles” get larger, the thorns disappear. Leaves are alternate, once pinnately compound 5 to 8 inches long with 7 to 17 leaflets. Each leaflet is 1 to 3 inches long, ovate or lanceolate, toothed, with several sharp prickles along the rachis. The flowers are pale green on loose wide-branched terminal clusters, 4 to 5 inches long. Z. clava-herculis blooms in the early spring. 

(Photo by Joseph A. Marcus, Wildflower Center Digital Library,  unrestricted)

Fruit and Avian Dispersal: The fruit ripens in the early summer, producing a loose cluster of dark brown one seeded capsules. Once the valves open, the small seeds are exposed. Seeds are quickly eaten by seed-loving (granivorous) birds. The fruit passes through the birds and is dispersed below the birds’ favorite resting places, along fence rows and the edge of the woods.

(Photo by Joseph A. Marcus, Wildflower Center Digital Library,  unrestricted)

Butterfly Host:   Z. clava-herculis serves as a host plant to a number of insect species including the Giant Swallowtail Butterfly (Palio cresphontes). Their “ugly” caterpillars which resemble bird droppings morph into a large, attractive butterflies.

(Photo by Dale Clark, Dallas County Lepidopterists’ Society

Related Plant Species: There are four species from the genus Zanthoxylum found in Texas. Z. clava-herculis overlaps in range with Z. hirsutum, which is also referred to as toothache tree. Z. hirsutum has five smaller leaflets and is common in West Texas.  

Z. clava-herculis is related to the Chinese-pepper tree,  Z. simulans, from eastern China. The fruit of this tree, the Sichuan pepper, produces the signature  mouth-numbing  flavor that  is  indispensable  in  the regional  cuisine of Sichuan, China.8

Same Name, Different Family: Aralia spinoza or devil’s walking stick is sometimes called Hercules club. It is a spiny shrub in east Texas with large twice compound leaves. A.spinoza is in a different family and does not resemble Z. clava-herculis.

Acknowledgement: We thank Ms. Dana Wilson, Dr. Wayne Meyer,  Mr. Bob Richie, and Ms. Sue Malnory  for their contributions to this article.  

1.      Texas A&M Forest Service (2014) Hercules'-Club Zanthoxylum clava-herculis, Trees of Texas.
2.      Sheryl Smith-Rodgers  (January 2011) FLORA FACT: TOOTHY CHEW, The toothache tree eases pain and hosts swallowtails. Texas Parks and Wildlife Magazine,   
3.      Lady Bird Johnson Wildflower Center Plant Database (September 14, 2015)
4.      Wikipedia. (2016) Zanthoxylum clava-herculis.
5.      Ferris Jabr ( September 14, 2016) Could Ancient Remedies Hold the Answer to the Looming Antibiotics Crisis? The New York Times Magazine,
6.     Dallas County Lepidopterists' Society (December 2008), Eastern Giant Swallowtail (Papilio cresphontes)  
7.   George A. Petrides and Janet Wehr (1988). Eastern Trees. Peterson Field Guides, New York, New York.

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