The New Student's Reference Work/Poisonous Plants

Poi′sonous Plants. Of the number found in the United States mention may be made of poison ivy, poison sumac, poison hemlock, water hemlock, pokeweed, corn cockle, black cherry, red buckeye, horse chestnut, laurel and jimson weed.



Poison-Ivy, a climbing or trailing shrub (sometimes erect), with variable three-foliate leaves, aërial rootlets and greenish flowers, appearing in May and June. The smooth, waxy fruit often remains on the plant until late in winter. The leaves often resemble those of the box-elder, as in the figure; but their margin is not seldom almost entire. They differ from those of the Virginia creeper in having only three leaflets instead of five. Poison-ivy grows everywhere in open brush, in ravines and on the borders of woods, and it is spread along roadsides and cultivated fields from seeds carried by crows, woodpeckers and other birds that feed upon its fruit in winter. The plant occurs abundantly throughout the United States as far as eastern Texas, eastern Kansas and Minnesota and in greater or less abundance throughout the less arid region of the west, with the exception of California, where it appears to be entirely replaced by Rhus diversiloba.



Poison-Oak plant differs from poison-ivy mainly in the character of its leaflets, which are somewhat thicker and smaller, more nearly elliptical and less sharply lobed. Their similarity to the leaves of the western oaks gives the plant its common name. The poison-oak thrives best on cool, westward mountain slopes and in ravines, but is quite generally spread throughout the Pacific coast from Lower California and Arizona to British America. It does not, however, frequent the higher mountains.

Poison-Sumac is an absorbent shrub six to 30 feet high, with long, pinnate leaves, having from seven to 13 entire 5 leaflets. The wood has a faint, sulphurous odor, which, together with the leaf scars, which are very prominent, enables one to distinguish the plant from other shrubbery in winter. It grows in swamps and in damp woods from Florida to Canada and westward to Louisiana. Poison-ivy, poison-oak and poison-sumac each produce about the same effect on the human skin.

Pokeweed shoots are often eaten for greens in the spring, but great care must be taken in so using the plant, as the root is very poisonous. The berries are greatly enjoyed by birds, though sometimes cases of poison have been traced to the fruit. It is a fine, sturdy plant, grows from five to ten feet high, the large smooth leaves are on long petioles, white and pink blossoms may be seen from July to September, the fruit is a generous bunch of juicy purple berries. The range of the plant is general, it grows on the outside border of fields.

Corn-Cockle grows in grain fields, bears blossoms of purple-red, adds no little to the beauty of a field but is a grievous pest. Its black seeds mix with the seeds of the grain; occasionally a low-grade flour will show some of the black of the corn-cockle’s seed-coats and cases of poison have resulted from the presence of corn-cockle in flour. Such flour has a peculiar odor when moistened. Corn-cockle stem is stout and many-branching; its leaves are pale green and hairy, the flower is terminal and solitary and may be seen from July to September.

Black Cherry seeds and leaves (see ) may contain enough prussic acid to cause poisoning; kernels should not be eaten; fresh-cut branches should not be put where cattle can get at them.



Seeds, fresh leaves and twigs of red buckeye and common horse-chestnut contain poison. The leaves of evergreen laurels have killed animals eating them. Jimson weed (Jamestown weed, thorn-apple etc.) getting into the hay of cattle proves disastrous, and poisoning has resulted from children handling flowers and eating seeds. It is a weed of bushy habit; it grows rank in waste places; the stem is from two to five feet high; the leaves are large and flaccid, the showy flowers, white or purple in color, in shape resemble the morning glory, but have a heavy, unpleasant odor. The purple variety is especially poisonous. The weeds belong to the nightshade family. It grows along roadsides, in pastures and in gardens. See Chestnut’s Thirty Poisonous Plants of the United States, Farmers’ Bulletin 86, U. S. Department of Agriculture.