Forest Preserve District of Cook County, Illinois
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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

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 wildlife value.

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 areas.

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. Qien sabe.

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 into syrup.

We will issue, next spring, a bulletin about the bizarre cactus family.

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