Prickly Ash and Prickly Pear
Nature Bulletin No. 649-A October 1, 1977
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation
PRICKLY ASH AND PRICKLY PEAR
In the plant kingdom, as among people, there are so-me that we avoid.
They have few virtues, if any, and our experiences with them are
painful or have unpleasant after effects. Poison ivy is a notorious
example. Prickly Ash, a shrub, is another. Although not poisonous it is
thickly armed with wicked thorns and has no ornamental, economic or
In 1821 when the first section lines were established in Cook County,
the surveyor recorded -- for the benefit of land buyers -- the principal
kinds of trees and other vegetation observed along each mile. He
frequently encountered prickly ash in thickets near the Little Calumet
River and also the north and south branches of the Chicago River.
In 1927, in his "Flora of the Chicago Region, " H. S. Pepoon observed
that it was more abundant north and west, notably at Edgebrook, in the
Skokie Woods, and along the DesPlaines River. Today, although
exterminated elsewhere, prickly ash survives in a few forest preserve
This many-branched shrub, usually from 5 to 10 feet high, sometimes
becomes a small tree 25 feet tall, with a trunk 6 inches in diameter, but
the wood is very soft and light. It is not a true ash. The compound
leaves, with from 5 to 13 pointed leaflets, grow alternately along the
twigs -- on an ash they occur in opposite pairs. At the base of each there
is a pair of short stiff flat spines and others occur along the petiole.
The prickly ash is closely related to the wafer ash or hop tree, and to the
citrus trees -- lemon, lime, orange, etc. The minute greenish flowers are
followed by tiny aromatic fruits. The bark, too, is aromatic because the
plant contains that alkaloid, xanthophyll, which also produces yellow
pigments. The bark of the southern prickly ash -- a much larger species
known as Hercules ' Club or Toothache Tree -- is collected and used as
a home remedy for toothaches and rheumatism.
In Florida, the larvae of the giant swallowtail butterfly, called "orange
dogs," sometimes defoliate orange trees. When disturbed, that big
caterpillar throws back its head and shoots out a pair of red "horns" that
exude an odor like that of putrid orange peels. And when this butterfly
spreads northward it occurs only where the larvae can feed on the
leaves of the hop tree and prickly ash.
The Prickly Pear, sole representative of the cactus family in the
Chicago region, also demonstrates that this is a melting pot of plants as
well as people. It may be an immigrant from the southwestern deserts or
it may be the survivor of a hot dry period that followed the ice age.
In 1927, Mr. Pepoon said that it was abundant on the low sand dunes in
southeastern Cook County. Now, apparently, only one patch remains: at
Powderline Lake in our preserve east of Burnham. It is being
reintroduced in the sandy preserves east of Thornton and in Shabbona
Woods, southwest of Calumet City, where our Sand Ridge Nature
Center is located.
This species of prickly pear cactus can be found also in the Illinois
Beach State Park north of Waukegan, the Indiana, and in sandy areas
throughout Illinois. Its prostrate branches, each a jointed series of flat,
spiny, succulent, pale green pads, bear beautiful yellow flowers. They
are followed by purplish pear-shaped fruits that -- with the needlelike
spines rubbed off -- are delicious when eaten raw, or candied, or made
We will issue, next spring, a bulletin about the bizarre cactus family.
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Update: June 2012