Part 1

Produced by Tom Cosmas compiled from images made available by The Internet Archive.

Transcriber Note

Text emphasis is denoted as: _Italics_ and =Bold=.

POISON-_ivy_

POISON-_oak_

and

POISON _sumac_

IDENTIFICATION PRECAUTIONS ERADICATION

Farmers' Bulletin No. 1972

U. S. DEPARTMENT OF AGRICULTURE

POISON-IVY, poison-oak, and poison sumac remind most people of painful experiences to be avoided, yet many do not know any one of the offending plants or their equally poisonous relatives. Learning to recognize them on sight is relatively easy, especially by examining the distinctive identifying characters described in the pictures and legends of this bulletin. There is then a good chance to avoid them or, if one must work among them, to take preventive measures to escape poisoning.

These plants are very common throughout the United States. They are found in fields and woods, along fence rows, rock walls, and hedges, in lawns and gardens, and even sometimes vining on houses. Usually in any one locality it is necessary to be certain of the identity of only two or three of them. Maps show at a glance where they are likely to be found. Frequent observation and recognition of the plants as they are encountered almost daily is the best way to become poison-oak or poison-ivy conscious. Nonpoisonous sumacs are easily distinguished from the poisonous species by the seed heads and leaves.

The old proverb, "an ounce of prevention is worth a pound of cure," is good advice to everyone, particularly as regards ivy-poisoning. Previous escape is not proof of immunity when conditions are right, and after poisoning occurs there is no quick cure known. Some relief may be obtained and recovery hastened by use of some of the tested remedies. In case of severe poisoning a physician should be consulted.

Poison-ivy and other poisonous plants growing in grounds frequented by people should be eradicated. In some places this can be done by careful grubbing. In others weed-killing chemicals may be better and more certainly would avert poisoning for most of us.

This bulletin supersedes Farmers' Bulletin 1166, Poison Ivy and Poison Sumac and Their Eradication.

Washington, D. C. Issued August 1945

POISON-IVY, POISON-OAK, AND POISON SUMAC: IDENTIFICATION, PRECAUTIONS, ERADICATION

By Donald M. Crooks, _principal horticulturist, Division of Tobacco, Medicinal, and Special Crops_, and Leonard W. Kephart, _senior agronomist, Division of Cereal Crops and Diseases, Bureau of Plant Industry, Soils and Agricultural Engineering, Agricultural Research Administration_

Contents

Page

A widespread menace to health 1 Forms of poison-ivy and poison-oak 2 Common poison-ivy 2 Oakleaf poison-ivy 9 Western poison-oak 9 Poison sumac 16 Confusion of poisonous and harmless sumacs 19 Introduced poisonous sumac and related species 21 Poisoning 21 Precautions against poisoning 22 Treatment for poisoning 23 Eradication of plants 25 Chemical weed killers 25 Eradication by mechanical means 25

A WIDESPREAD MENACE TO HEALTH

EVERY year sees many adults, and especially children, accidentally poisoned from contact with plants that they did not know were harmful. Had the sufferers known how to detect poisonous plants they could have avoided them and escaped the painful experience of severe skin inflammations and water blisters. Very few persons have a sufficient degree of immunity to protect them from poisonous plants, and many do not recognize them in the various forms that they assume in different parts of the country.

One or more kinds of poison-ivy--common poison-ivy, oakleaf poison-ivy, and western poison-oak--occur in abundance in almost every part of the United States. Poison sumac is of more limited distribution and occurs chiefly east of the Mississippi River, usually in swampy regions.

Poisoning by these plants is largely preventable. A knowledge sufficient to identify them in their various forms is easily gained by anyone who will make a study of pictures and general descriptions and train himself by a little diligent practice to observe the plants in his locality. It is important to become poison-oak or poison-ivy conscious. This can be accomplished only by learning to know the plants by repeated experience in observing them in their various forms. Persons who learn both to know and to avoid the plants can save themselves much inconvenience and discomfort. The simple means of learning to recognize them will pay big dividends. It is the first step to the prevention of poisoning and to the eradication of the pests from private grounds and public places.

The most effective method of prevention is to eradicate the plants, and wherever possible this should be done. They should not be allowed to grow in lawns or gardens, with ornamental shrubbery, or on houses. Communities should not countenance the growth of poison-ivy or poison-oak in school grounds, on public roadways, or in parks, especially those frequented by children. The cost of medical aid for one season in treating pupils using an ivy-infested schoolyard is likely to be more than that of eradicating the plants, to say nothing of the suffering and inconvenience they may cause.

FORMS OF POISON-IVY AND POISON-OAK

Poison-ivy and poison-oak are known by a number of local names, and several different kinds of plants are called by these names. The plants exhibit a good deal of variation throughout the United States, so much so that even technical botanists cannot agree on the number of species and names that should be applied to them. They grow in the form of (1) woody vines attached to trees or objects for support, (2) trailing shrubs mostly on the ground, or (3) erect woody shrubs entirely without support. They may flourish in the deep woods, where soil moisture is plentiful, or they may be found in very dry soil on the most exposed hillsides. The plants are most frequently abundant along old fence rows and edges of paths and roadways, and they ramble over rock walls and climb posts or trees to considerable heights. They often grow with other shrubs or vines in such ways as to escape notice.

The leaf forms among plants or even on the same plant are as variable as the habit of growth; however, the leaves always consist of three leaflets. The old saying, "Leaflets three, let it be," is a reminder of this consistent leaf character but may lead to undue suspicion of some harmless plant. Only one three-parted leaf leads off from each node on the stem. The leaves never occur in pairs along the stem. The wide range in habit of growth of plants and leaf types may be noted from a glance at the several pictures of plants and leaves.

The flowers and fruit are always in clusters on slender stems that originate in the axis of the leaves along the side of the smaller branches. The fruits usually have a white, waxy appearance and ordinarily are not hairy, but may be so in some forms. The plants do not always flower and bear fruit. The white or cream-colored clusters of fruit, when they occur, are significant identifying characters, especially at the season after the leaves have fallen.

For convenience, these plants are discussed in this bulletin under three divisions: (1) Common poison-ivy, (2) oakleaf poison-ivy, and (3) Western poison-oak. A technical botanist would recognize many species of plants in what are included as the common poison-ivy, and anyone will recognize that various forms occur within this grouping.

COMMON POISON-IVY

Some form of the common poison-ivy may be found in almost every part of the country but the extreme West. The shaded area on the map in figure 1 shows the extensive range where some form of poison-ivy is likely to be found. The plant is known by various local names--poison-ivy, threeleaf ivy, poison creeper, climbing sumac, poison-oak, markweed, piery, and mercury. The most widespread form is classified by botanists under the botanical name of _Rhus radicans_ or varieties of it; however, many of the variations are sometimes given other botanical names. The common poison-ivy may be considered as a vine in its most typical growth habit.

_Figure 1._--The shaded part shows the extensive area where some form of the common poison-ivy is likely to be found. Other forms also may occur in parts of the same region.

_Figure 2._--Large poison-ivy vine growing on a tree for support. This is the usual form of the common poison-ivy in wooded areas.

_Figure 3._--_A_, Common poison-ivy growing in a hedge and on a shade tree on the edge of a lawn. _B_, Typical vine, showing leaves and the roots that attach it to the tree.

The vining type most often occurs in wooded areas (fig. 2), where it depends upon trees for support. Vines often grow for many years, becoming several inches in diameter and quite woody. Slender vines may run along the ground, mixed with shrubbery, or take support from a large or small tree. That a plant growing along the edge of a lawn and into the shrubbery may be quite inconspicuous as compared with a vine climbing on a lawn tree is shown in figure 3. The vine readily develops roots when in contact with the ground or with any object that will support it. When the vines grow on trees these aerial roots attach the vine securely ( fig. 3. B). A rank growth of these roots often causes the vines on trees to have the general appearance of a "fuzzy" rope, which sometimes serves a good purpose for identification. The vines and roots apparently do not cause injury to the tree except where growth may be sufficient to cover the supporting plant and exclude sunlight or break the plant from excessive weight. The vining nature of the plant makes it well adapted to climbing over stone walls or on brick and stone houses.

The fact that poison-ivy often becomes mixed in with ornamental shrubbery and vines often results in its cultivation as an ornamental vine by people who do not recognize the plant. An ivy plant growing on a house, as is shown in figure 4, is often prized by an unsuspecting owner. The vine is attractive and quite effective as an ornamental, but such use should not be tolerated, as it most certainly will result in cases of accidental poisoning and serve as propagating stock for more poison-ivy in the vicinity.

_Figure 4._--Common poison-ivy growing on side of house with ornamental shrubs. This accidental or intentional use of the attractive vine may lead to many cases of accidental poisoning.

_Figure 5._--Common poison-ivy growing along fence row. In open sunlight and over some large areas it is more of a shrub than a vine.

_Figure 4._--Common poison-ivy growing on side of house with ornamental shrubs. This accidental or intentional use of the attractive vine may lead to many cases of accidental poisoning.

When poison-ivy becomes mixed in with other vines it is quite difficult to detect except by one who has carefully trained himself in observing and recognizing the plant. Also, some other vines and young plants resemble poison-ivy in many respects. The Virginia creeper and some forms of the Boston ivy are often confused with it. The Virginia creeper can always be recognized by its five leaflets radiating from one point of attachment, as compared with the three leaflets of poison-ivy arranged in the same manner. The Boston ivy with three leaflets is sometimes difficult to detect; however, as a rule not all the leaves on the plant will be divided into three leaflets. By studying a large number of the leaves it is usually possible to detect on every Boston ivy plant some leaves that have only one deeply lobed blade or leaflet, while the poison-ivy always has the three leaflets. A number of other plants are easily confused with poison-ivy. No specific rule can be observed that will easily rule out all possibility of confusion. The best policy is to learn through practiced observation to know poison-ivy on sight and then to make the determination from observation of all parts of the plant, and never to judge from a single leaf or part.

_Figure 6._--Leaves of common poison-ivy, about half natural size. These may occur on the same or different plants: _A_, _B_, _C_ and _F_, less common; _D_, with even margins, the most common and generally recognized form; _E_, with lobed margins, nearly nearly as often seen as the shape in _D_.

_Figure 7._--Common poison-ivy vine with clusters of flowers in the axis of each leaf.

Common poison-ivy in full sunlight along fence rows or in open fields grows more in the form of a shrub than a vine. In some localities the common form is a low-growing shrub from 6 to 30 inches in height. This form, as well as the vining type, usually has a rather extensive horizontal system of rootstocks or stems at or just below the ground level. The vining form under some conditions later becomes a shrub. Plants of this type are shown in figure 5, where the vine, supported on the fence, has extended upright stems that are shrublike. In some localities the growth form over a wide range is consistently either a vine or a shrub type, while in others what seems to be the same species may produce either vines or shrubs.

The leaves of the common poison-ivy are extremely variable, the three leaflets being the only constant character. It is impossible to describe the great range of variation in the shape or lobing of the leaflets. A study of the leaf patterns, especially the six shown in figure 6, will give a fair range of types, although other forms may be found. One plant may have a large variety of forms of leaves or it may have all leaves of about the same general character. The most common type of leaf having leaflets with even margins is shown in figure 6, _D_, and one with leaflets having slightly lobed margins is shown in figure 6, _E_. The other forms shown in figure 6 are not quite so widespread, but may be the usual type throughout some areas.

_Figure 8._--Common poison-ivy, about natural size: _A_, Flowers; _B_, mature fruit.

Most of the vines or shrubs of poison-ivy produce some flowers that are always in clusters arising on the side of the stem immediately above a leaf. The flowers are rather inconspicuous among the leaves, as may be noted in figure 7, but they are in quite distinct clusters, as shown in figure 8, _A_. Frequently the flowers do not develop or are abortive and no fruit is produced. When fruits do develop they serve as a positive way of identifying the plant. The berries are not easily confused with the fruits of other plants. They are white and waxy in appearance and have rather distinct lines marking the outer surface, as the segments appear in a peeled orange. These lines may be noted in figure 8, _B_, which shows dense clusters of mature fruit about natural size. Some forms of the poison-ivy have the fruit covered with fine hair, giving it a kind of downy appearance; however, in the more common form the fruits are entirely smooth. The fruit is especially helpful in identifying plants late in fall, in winter, and early in spring, when the leaves are not present.

_Figure 9._--The shaded area is the region where the eastern oakleaf form of poison-ivy is likely to occur. Other forms also may be in the same region.

OAKLEAF POISON-IVY

Of the several kinds of poison-ivy, the oakleaf form occurring in the Eastern and Southern States is more distinctive than some other types. Some people know it as oakleaf ivy while others call it poison-oak, a name more commonly used for the western species discussed later. Botanists have not always agreed upon the scientific name to be applied to this form; however, they now use the name _Rhus toxicodendron_. Some botanists have used the Latin names _R. quercifolia_, while others used the name _Toxicodendron quercifolium_, both of which are more descriptive of the oakleaf form, as the generic name of the oak is _Quercus_. The area where the oakleaf form may occur, from New Jersey to Texas, is outlined in the map shown in figure 9. The common poison-ivy also occurs in some form throughout many parts of this same area.

The oakleaf poison-ivy usually does not climb as a vine, but occurs as a low-growing shrub. Stems are usually upright in their general growth habit, as they appear in figure 10. The shrubs usually have rather slender branches, often covered with a fine pubescence that gives the plant a kind of downy appearance. The leaflets occur in threes, as in other ivy, but are lobed, somewhat on the general plan of the leaves of some kinds of oak. The middle leaflet usually is lobed somewhat alike on both margins and very much resembles a small oak leaf, while the two lateral leaflets are often irregularly lobed. The leaves shown in figure 11 are a common form. The lighter color on the under side of one of the leaves (fig. 11, _A_) is due to the pubescence, or fine hairs, on the surface. The range in size of leaves varies considerably, even on the same plant; the leaf shown in figure 11, _B_, however, is about natural size.

The fruit of oakleaf poison-ivy has the same general appearance as the fruit of common poison-ivy shown in figure 8, although the individual fruits and stems are often pubescent, while most of the other forms have a waxy, smooth, cream-colored fruit.

_Figure 10._--Eastern oakleaf poison-ivy shrub. The upright growth as a low shrub is common. The three parts of each leaf somewhat resembles an oak leaf. The gall formations that cause wartlike protuberances are common on all species.

_Figure 11._--Eastern oakleaf poison-ivy: _A_, Leaves, showing upper deep green surface and lower lighter colored surface. _B_, Single leaf, about natural size. The terminal leaflet more nearly resembles an oak leaf than the two lateral leaflets.

WESTERN POISON-OAK

The western poison-oak (_Rhus diversiloba_) of the Pacific Coast States is usually known as poison-oak, but is occasionally referred to as poison-ivy or yeara. It is likely to be found in the region designated by shading in figure 12, and from central Oregon northward through Washington may be growing intermixed with common poison-ivy. The term "poison-oak" is a misnomer, as this species is in no way related to the oak but is related to poison-ivy. Anyone familiar with either of these plants in their several forms will likely recognize the other, both as plants to be avoided.

_Figure 12._--The shaded area is the region where the western poison-oak is likely to occur. Other forms may also be in the same region.

The most common growth habit of the western poison-oak is in the form of a rank upright shrub with many small woody stems rising from the ground. It frequently grows in great abundance along roadsides (see fig. 16) and in uncultivated fields or on abandoned land.

Sometimes western poison-oak attaches itself to upright objects for support and takes more or less the form of a vine. A plant of this type is shown in figure 13, where it is growing on a telephone pole by the roadside. It may be noted even in this case that the tendency is for individual branches to continue an upright growth rather than become entirely dependent upon other objects for support. In some areas, especially in woodland, poison-oak may grow principally as a vine. Areas have been noted where 70 to 80 percent of the trees leaves and flowers. in a wooded area support vines running more than 25 or 30 feet in height, although the most common form of the plant is the shrub.

_Figure 13._--Western poison-oak on a telephone pole. This vine form is not uncommon, especially on trees in woods.

_Figure 14._--Western poison-oak: Upright shrub, with fruit, growing in open pasture field.

_Figure 15._--Western poison-oak, showing common leaf types: _A_, The more common leaves with irregular margins; _B_, less typical, although not uncommon, leaves with even margins.

_Figure 16._--Western poison-oak growing alongside roadside. This rank shrubby growth is typical for most localities.

_Figure 17._--Western poison-oak, showing common leaf types: _A_, Leaves with thick leathery appearance; _B_, leaves irregular in shape with much-curled or distorted surfaces; _C_, branch, with leaves and flowers.

In open pasture fields western poison-oak usually grows in spreading clumps from a few feet to several feet tall (figs. 14 and 16). Where it develops extensively it greatly reduces the area for grazing and becomes a serious menace to most people who frequent the area or attend cattle that come in contact with the plants while grazing.

_Figure 18._--Western poison-oak: _A_, Top of shrub, with leaves and fruit; _B_, clusters of fruit after leaves have fallen.

Low-growing plants, especially those exposed to full sunlight, are often quite woody and show no tendency for vining. Low-growing plants with woody stems are common in pasture areas or along roadsides. Livestock in grazing do not invade the poison-ivy shrub, and as a rule these plants continue to spread both by root-stock and seed.

As in other ivy the leaves consist of three leaflets with much irregularity in the manner of lobing, especially of the two lateral leaflets. The Latin name _dirersiloba_ refers to the irregularity occurring in the shapes of the leaves on different plants and on the same plant or even irregularity in the lobing of leaflets of the same leaf. Sometimes lobes occur on both sides of a leaflet, thus giving it somewhat the semblance of an oak leaf. The middle or terminal leaflet is more likely to be lobed on both sides and resembles an oak leaf more than the other two. A study of the leaves shown in figures 15 and 17 shows the variation in lobing. Some plants may have leaflets with an even margin and no lobing whatsoever, as those in figure 15, _B_. The surface of the leaves is usually glossy and uneven, so that they have a thick leathery appearance.

_Figure 19._--A large poison sumac shrub about 15 feet tall, growing on the edge of a swamp.

The flowers are borne in clusters on slender stems diverging from the axis of the leaf, as may be noted in figure 17, _C_. The individual flowers are greenish white and about one-fourth inch across. The cluster of flowers matures into greenish or creamy-white berrylike fruits about mid-October. These are about the size of small currants and are much like other poison-ivy fruits, having a smooth greenish-white glossy surface striped somewhat like the segments of a peeled orange. Many plants bear no fruit, although others produce it in abundance, as shown in figure 18, _A_. The fruits are not always spherical, but sometimes have a somewhat flattened appearance, as is shown in figure 18, _B_. They remain on the plants throughout fall and winter and are quite helpful in identifying poison-oak in seasons after the leaves have fallen.

_Figure 20._--The shaded area shows the region where poison sumac is likely to occur in bogs or swamps, although isolated plants are sometimes found in dry soil.

POISON SUMAC