Nature's Poison: Ivy & Oak

Rhus radicans & Rhus diversiloba

Author:Takiyah Booker

Anacardiaceae is a member of the Sumac Family in which the genus Rhus and Toxicodendrum are found. Founded by Lindley in 1830 num. consevrv.,this family includes: trees shurbs, or woody vines, with vertical schizogenious resin - ducts in the bark and pholem of the veins in the leaves. Anacardiaceae often come in the flowers and in the pith and other parenchyratus tissues. The resin of these plants are often allergenic or poisonous to the touch. The leaves are alternate, or rarely opposite or whorled, pinnately compound or trifoliolate. Flowers are in terminal or auxillary, sometimes complex. This family consists of of sixty to eighty genra and approximately six - hundred species. Anacardiaceae is chiefly pantropical in distribution and some species habitat temperate regions. The largest genus is Rhus with one hundred species. The genus, Toxicodendron includes poison ivy, poison oak and poison sumac. Toxicodendron is notorius for causing dermatitis in some individuals but the genera metopium are nore potent. Archeologically, Rhus occurs in Eocene deposits in Yellow Stone National Park. This is the oldest fossil pollen of the family and it comes from the Paleocene of Europe. The plants producing 5 deoxyflavoroids and biflavonils containing solitary or clustered crystals of calcium oxalate are present in the parenchymatous tissues and silica grains are some time present in the xylem cells.

The flowers are terminal or axillary and cymose inflorescences. They are small, regular, hypogynous perfect or unisexual. The unisexual flowers often have nonfunctional parts of the other sex. The sepals of the flower and petals each are (3-)5(-7) valvate or imbricate and cannate below with distinct petals. The filaments are rarely cannate at the base and found within the annular often a 5 - lobed nectary - disk or into short , stout aynophore. The anthers are dithecal, opening by longitudinal slits and the pollen grains are binucleate, triporate and less than often 4 - 8 porate. The fruit is resinous and might appear waxy or have an oily mesocarp. the seeds are also oily with a curved emgryo and 2 expanded cotyldons containing little or no endosperm (Cronquist, 1988). See Rhodora for key 1971

Identifying Poison Ivy

Rhus radicans (Poison 2Ivy)

The original description of the species is found in Plantarium. Linneaus discovered it May 1, 1753 and it moved to the genus Toxicodendrum (Gray, 1978). Climbing poison ivy carries the genus of Toxicodendrum and the species of radicans. Its original scientific name, Rhus radicans, still is used and appears in botanical literature but is replaced by the most recent name of Toxicodendrum radicans.

Some characteristics that are easily observed again are the trifoliates, the alternate leaves, this resembles a clover plant. The aerial roots, which are short hairlike structures on the climbing poison ivy, have a fuzzy reddish appearence on the stems of young climbers. However, with age the aerial roots turn a greyish - black or rusty color. The hairs secrete a glueish material that anchors the stem to the trunk of tree, wall or any other structures. Climbing poison ivy have thick clusters of waxy, whitish fruits a;long the female flowers and each drupe has lines on the its underside covered with fine hairs. During the winter, climbing poisonivy is leafless and fruitless. A vine, stem or rhiozome with alternate, fuzzy stalked and naked bud is usually poison ivy. The woody stems of climbing poison ivy, attached to a tree trunk and the leaf variety of climbing poison ivy are noticed.

Rhus radicans is a glossy perennial that spreads by seeds and woody rhizomes. It is a trailing vine, a subshrub to shrub 5-120 cm high, or an aerial-rooted vine that climbs rough surfaces to 15 m. The leaves are alternate and consist of three leaflets; the middle one has a stalk much longer than those of the two lateral leaflets. The edges of the leaflets may be smooth or rough. The leaves vary in size, from 8 to 55 mm long. As the seasons change the color of Rhus radicans leaves change too: when they first emerge in the spring the leaves are reddish; in summer, the leaves are green; in the fall they are various shades of yellow, orange, red, or bronze. Male and female flowers, found on separate plants, which are clustered, small, cream to yellow green in color and 3-7 mm in diameter and 1-seeded (Mitich,1995).

Rhus diversiloba(Poison Oak)

The original description of poison oak is found in A flora of North America Book, Tarrey and Gray considered it of the genus Toxicodendrum. Rhus diversiloba was discovered by Douglas at Fort Vancouver on the Columbia River about 1830. In 1831 W.J. Hooker gave poison oak its botanical significance as Rhus lobata. To support his discover he gave the following reasons:

Its general habit is very different,having erect straight stems and numerous small leafy branches. The leaflets besides being deeply lobed with acute sinuses are truly ovate, very obtuse, and greatly smaller than any state of R.Toxicodendron, or R. radicans, which I have seen; the panicles, too are exceedingly numerous.

. A free translation of Hooker's Latin description of the plant is as follows:

"Bush erect, 3-4 feet, branches round with the youngest ones pubescent, branche numerous, short, spreading,leafy. Leaves long-petiolate, trifoliate, with little leaves ovate, 1-2 inches long, very obtuse, membranaceous, at the base sometimes acute, sometimes rotund or truncate, beneath especially pubescent, deeply and variously lobate, terminate one sub-long petiolate, each side sub-equally lobate with lobes generally less than 3, with little lateral leaves at the exterior margin more deeply lobate. Flowers (male) yellow, in loose racemes, shorter than leaf, longer that petiole. Bracts at the base of the branches oblong, ciliate. Calyx deeply parted with oblong lappets. Petals 5, much longer than the lappets of the calyx,obovate into a tongue evidently with attenuated base, at the back veined. Stamens 5, erect, little shorter than petals. Filaments subulate. Anthers 5, somewhat more greatly ovate, pale yellow, with cells sub-opposite. Style small, extending from the center of a platter-shaped disc situated in the bottom of the calyx,margin of the disc elevated, curled."

Torrey and Gray furthered the botanical knowledge of the plant by noticing:

"The sterile and fertile flowers of this species (which is very near R. Toxicondendrum) present some notable differences. The sterile, which is figured by Hooker, has rather deeply lobed leaflets, sometimes in fives and larger flowers; in the fertile the leaflets are almost entire or slightly lobed and the flowers considerably smaller, so that it might readily be taken for a distinct species. The fruit is white, somewhat pubescent and gibbous."

Torrey and Gray renamed the plant Rhus diversiloba, the most common name(Jones,1986).

SPECIES LIST

IDENTIFICATION GUIDE Rhus radicans or Toxicodendrum radicans(L.) Kuntze and Rhus diversiloba Toxicodendrum diversiloba (T.&G.)Greene

Background

The genus of Toxicodendrum has been used in the treatment of eczema, shingles and ringworm. The sap, which turns black on air contact, is used for dye. Rhus toxicodendrum has been used in the treatment of paralysis, obstinate herpatic eruptions, palsey and in chronic obstinate eruptive diseases. Some Native Indians used Poison Oak in basket weaving; therefore, the Indians must have developed some kind of immunity to Poison Oak. Poison Ivy also belongs in the genus of Tocicodendrum and its reproduction along with Poison Oak is due to birds transporting the seeds. Then the seeds can root and grow. Poison Oak and Poison Ivy can survive in all types of temperatures, elevations, soil types, moisture and light intensities. Both Poison Ivy and Poison Oak have economic significances. Poison Ivy have been cultivated in gardens and sold as an ornamental by French nurserymen. The two species also have horticultural values. The color of their autumnal foilage are used for fruit shows for display. Both species have been planted along the dikes of the Netherlands for dike consolidation. Also, horses and cattle occasionally browse without effects. Birds and quails feed on its fruits. The Ramah Navahoes made an arrow of poison from the poisonous sap for hunting and fighting. The Yuki tribe of California used sap to cure warts, ringworm and snakebites. Both species flower around the same time, between the end of January and the middle of February in the eastern southern states or in mid-May or early June in the Atlantic states. Within the flowering times, there are times of maxima flowering between the second week in June and the first week in July for northern Honshu(Gillis, 1971).

For More Info Visit: EDA