Photo: Eric Hunt, CC BY-SA 4.0 · Wikimedia Commons

Hercules' Club

Zanthoxylum clava-herculis

Also called southern prickly ash, southern toothache tree, pepperbark, tingle tongue, tickle tongue, Zanthoxylum macrophyllum.

A spiny little tree of the southern coastal plain, its trunk studded with corky knobs, its leaves able to numb the tongue and feed giant swallowtails.

Wildlife valueDrought tolerantHedge or screen

Type: Small tree
Mature height: 15–40 ft
USDA zones: 6–10
Growth rate: Medium
Sun: Full, Part
Soil moisture: Dry, Average
Grows wild in: The coast, sandy barrens, stream banks, old fields and edges
Native range: 11 states, north to Virginia, south to Florida and west to Texas
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Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Texas and Virginia
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Hercules' club is a spiny tree of the citrus family, named for the club of the Greek hero. Its gray trunk bears large corky knobs, each tipped with a spine that wears away with age. The leaves, bark and flowers smell strongly when bruised. Chewing the bark or leaves numbs the mouth, so Native Americans and settlers used it for toothache. It is the southern cousin of our common prickly ash, and like it a larval host of the giant swallowtail. Devil's walking stick, a spiny shrub of the ginseng family, is called Hercules' club too; it is a different plant. Grow it in a hedgerow, a screen or a wild corner of sandy ground.

Size, growth and what to expect

No source we read rates its growth, so our growth estimator uses its middle figure, about a foot and a half a year. Expect 15 to 40 feet, with a crown 10 to 25 feet wide. It rarely reaches 50 feet and often stays a large shrub.

Small yellow-green flowers open in April and May in large clusters at the branch tips, and male and female flowers grow on separate trees. On female trees the seed pods ripen from July to September, splitting to show shiny black seeds that birds and small mammals eat.

It grows wild on the Atlantic and Gulf coastal plain from Virginia to Florida, west to eastern Texas and north to southeastern Oklahoma. It favors sandy soil in maritime forests, on dunes and along riverbanks. Virginia keeps it on its watchlist of uncommon plants.

How to grow Hercules' Club

Hercules' club grows in full sun or part shade, in sandy or loamy soil that drains well, and it takes dry spells. It tolerates poor soil. Keep it back from paths, since the trunk and branches bristle with spines. Plant it 15 feet from a wall and at least 15 feet from overhead wires, and set trees 15 feet apart.

Saplings ship bare-root or potted. Plant them dormant, from leaf fall until bud swell, in a hole wider than the roots and no deeper, and wear gloves. Set the root flare at the soil line, put the native soil back in, and keep the mulch clear of the trunk. The seed has a hard coat that keeps it dormant, and it sprouts poorly. Sow it outdoors in fall as soon as it is picked. Even acid-treated seed averaged 31 percent germination in tests.

Water weekly through the first summer if rain is short, then only in a long drought. It spreads by root suckers into a thicket, so cut them at the ground, in gloves, wherever a single tree is wanted.

Trees are male or female, and only females bear the seed pods, so plant three or more seedlings for a male and a female. Giant swallowtail caterpillars can strip much of the foliage in some years. Otherwise it has no serious insect or disease problems.

Heights and zones are typical ranges for the species in cultivation; local conditions and seed source shift them.

Sources (9)