Heroic Hercules Club

Hercules club (Zanthoxylum clava-herculis) is easily identified by the pyramidical protuberances on its trunk – each armed with a spine. The species name, clava-herculis, reflects this common name. The species name, Zanthoxylum, refers to the yellow wood of this plant.

With time the thorns are worn away, but the protuberances remain. This trait can be important when this deciduous tree is leaf-less.

Reddish spines adorn its odd compound leaves and give rise to another common name: southern prickly ash.


Its branches also are thorny, as shown in this photo by Karen Schuster (Class of 2008) taken at Pelican Island National Wildlife Refuge.

!!zanthoxylum clava herculis w giant swallow by kg

Toothache tree is yet another common name for this plant. Its leaves and bark contain a numbing compound housed in the pellucid dots visible in the photo below. Just chew upon a soft, young leaf to experience a pleasant citrusy flavor and its mouth-numbing capabilities.

!!!!zanthoxylum w pellucid dots copy

On our 3/19/2016 special tram tour at Pelican Island National Wildlife Refuge, the hercules club along the Centennail Trail was both blooming and beginning to fruit.


Its tiny flowers are borne in terminal panicles and are very attractive to pollinators.


Hercules club is dioecious; Some plants have male flowers, and other plants hold the female flowers. Pollinators transfer pollen from male plants to female plants.

The fruits are borne in terminal panicles on female plants (of course). The follicles will be tan-brown when ripe and will split open to reveal a shiny, hard black seed. Birds consume and spread the seeds.

Hercules club is a member of the citrus family, Rutaceae. Like the exotic citrus of commerce (oranges, grapefruit, limes, and lemons), hercules club is a larval food for the giant swallowtail butterfly (Papilio cresphontes), also known as the orangedog butterfly.

!!!!giant swallowtail 3-25-2009 copy

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