English Ivy

English Ivy Patapsco Tree Dec2014
It is the best of vines and the worst of vines

Common Name: English Ivy, Common ivy, Ivy, Bindweed, Lovestone – The name ivy is of ancient provenance, and may derive from either the Latin ibex, meaning ‘climber’ or from the Old English ifig. The native Eurasian plant was introduced to North America by English colonists in the early 18th Century.

Scientific Name: Hedera helix – The generic name Hedera is the Latin word for ivy; the species name helix is the Latin word for ‘something spiral in form’. Alternative scientific names include H. acuta (pointed ivy), H. arborea (tree ivy) and H. grandiflora (large flowered ivy).

Potpourri: It is the best of vines and the worst of vines; while apologies may be due Charles Dickens, he shares Britannic origins with the toponymic English ivy that is at once a boon and a bane. It is beloved as a horticultural groundcover and lofty evergreen cloak for drab buildings and pergolas; it is loathed as an invasive that creates an axenic ivy desert at the expense of native plants and parasitically uses trees for the support that its spindly stems lack. It is planted and nourished assiduously in some parts of North America and eradicated as a pest in others. While it wreaks less havoc to the skin than poison ivy, it does cause skin dermatitis in some people. While it is not as beneficent as the vines of the fox grape, its berries are relished by many birds as one of few winter foods. It is a tale of two vines.

Englsih Ivy Juvenille Leaves Harpers Ferry 150131
The ground-dwelling, juvenile form is the familiar ivy with the characteristic palmately-lobed leaves

English ivy comes in two forms and is able to transform from one to the other based on the occasion of its growth and habitat. The ground-dwelling, juvenile form is the familiar ivy with the characteristic palmately-lobed leaves that extend vegetatively with thin roots in all directions, a vast monoculture mat the result. A heliotropic, climbing and creeping vine; it ascends anything that offers elevation with alacrity, covering the sides of buildings and boles of trees with garlands of green. The root and stem structure of the juvenile form is thin and non-penetrating, serving only to anchor the vine. The trees and structures to which it is attached are generally not directly affected, as they are not penetrated for nutrient extraction.

English Ivy Patapsco Leaves Dec2014
The mature leaf form changes to cordate – heart shaped

As the juvenile form has no flowers and therefore no berries for propagation, a transition to a reproductive form is necessary. This occurs once the plant has reached an elevation of about five feet. For reasons that are not clear, the leave form changes in the mature, reproductive plant from palmate to cordate (heart shaped). The stem thickens to the point that it is self-supporting, able to carry the weight of the flower and subsequent berries. The elevation of the flowers and berries is clearly an evolved trait to take advantage of aerial pollinators and, more importantly, to display the succulent fruit to attract birds for their digestive seed dispersal. Its success in this enterprise is evident in the dominance of its reach in its mid-northern latitude habitat.

Hedera spp has a complex taxonomy that is not all that well defined. In the ubiquitous language of DNA sequencing, the genus Hedera has been determined to be monophyletic (i.e. extending from a single ancestral type) by “maximum parsimony and Bayesian analysis.” Based on the fact that the greatest genetic diversity occurs in northern Africa and southern Europe, it is postulated that ivy originated in the Mediterranean and diverged into species through allopatry, or geographic isolation. Genetic analyses of the various Hedera species in a single area have revealed that genome duplication is frequent and that therefore hybridization occurs quite readily with variations in leaf morphology and size the result. The labile characteristics of the ivies make classification virtually impossible, a fact exacerbated by the intentional hybridization by horticulturalists to achieve a desired aesthetic effect. The American Ivy Society has so many cultivars that they have found it necessary to divide them into groups that range from Bird’s Foot ivies (BF) to Oddities (O) to include a superfluous ivy-ivy (I). As these have spread from lawn and garden to woodland in supplement to the original introduced English ivy, the British invasion has been compounded by multiple mutations.

English Ivy Invasion Harper's Ferry 150131
There are two issues with the spread of the hybrid Hedera varieties: damage to trees and damage to diversity

English ivy is banned as an official noxious weed in Oregon and Washington and is considered invasive in sixteen other states and the District of Columbia. The necessary anathema toward ivy of the Pacific Northwest is a tale of two regions – the climate emulates that of England where the namesake ivy flourishes; however, it has none of the native checks and balances. There are two issues with the spread of the hybrid Hedera varieties: damage to trees and damage to diversity. Ivy vines use the tree bole only as a prop to enhance photosynthetic capacity and not as a source of nutrition; there is no direct parasitism. The tree damage problem is thus indirect; the massive plexus of the vine stems and leaves that add weight not accounted for in the arboreal root structure, the etiolated tree becoming more susceptible to blow down in high winds. A secondary problem with the ivy shield is that it is susceptible to bacterial leaf scorch (Xylella fastidosa), which can then spread to the host tree, burning the leaf margins to contribute to the tree’s ultimate demise. The diversity problem is that which is shared by all invasive species, outcompeting native plants due to superior growth and spreading adaptations. A study conducted in Seattle compared an ivy-infested area with one that was ivy free and concluded that substantial diminution of native species in the former. The USDA has one recommendation for its control and management: “Do not plant English ivy.”

English Ivy Berries Harper's Ferry 150131
Ivy is spread by birds attracted to its berries

The leaves and berries of English ivy contain a triterpene glycoside named ɑ-hederin (from the genus Hedera) that is mildly toxic if ingested, with symptoms ranging from gastrointestinal distress to muscular weakness. This then provides the all-important answer to the question in the novelty song Mairzy doats: “Mares eat oats and does eat oats and little lambs ear ivy, a kid will eat ivy too, wouldn’t you?” The proper response would be no. However, the berries are eaten by frugivorous birds which are apparently not repelled by the taste, but who do reportedly become diarrheic. This is thought to contribute to the rapid distribution of the ivy seeds with bird excrement soon after consumption thereby enhancing the plant’s invasive spread. As ivy seeds require scarification to germinate, the cutting of small holes is apparently achieved as well during the avian ingestion and digestion process. Ivy is generally shunned by other animals, though there are reports that sheep and deer will occasionally eat them in the winter. The toxic triterpene glycosides presumably produced by H. helix to deter consumption by herbivores are also a good source of medicinal compounds; both ginseng and black cohosh contain them. This is the reason that English ivy has a long history of use for the treatment of various maladies that extends at least to the Roman Empire.

John Gerard was a leading English herbalist of the 16th Century who noted in his opus Of the Historie of Plantes that “Ivy, as Galen saith, is compounded of contrarie faculties, for it hath a certaine binding earthy and cold substance and also a substance somewhat biting.” Among the treatments Gerard accorded to the prominent Roman physician Claudius Galenus known as Galen were that “The leaves of Ivie fresh and greene boyled in wine do heale old ulcers ….and are a remedy likewise against burnings and scaldings” and “The juice drawne or snift into the nose doth effectually purge the head and staieth the running of the eares.” However, Gerard also notes that ivy “in our time is seldom used, save that the leaves are laid upon little ulcers made in the thighs, legs and other parts of the body … for they draw humors and waterish solutions to these parts.” Nicolas Culpeper, writing some fifty years later in the 1659 Complete Herbal, was much more positive about the attributes of ivy, claiming, among other things, that it would prevent and heal the plague, ease the long-standing headache, and cure all burns and scalds and “all kind of exulcerations coming thereby, or by phlegm or humours in other parts of the body.” Perhaps the most normative of the benefits of ivy was its use in offsetting the deleterious effects of bacchanal. Bacchus, the Roman god of wine and revelry, a cultural adaptation of the Greek Dionysus, is generally portrayed with a garland of ivy, imputing its importance as a shield against inebriation. It is not without some irony that Greek priests presented newlyweds with a wreath of ivy to supposedly indicate fidelity, the diametrical opposite of bacchanal. The palliative properties of ivy for alcoholic excess persisted in signage at some early English public houses (pubs) that included a sprig or bush of ivy to indicate that the spirits served therein were pure giving rise to the apothegm “good wine needs no bush.”

English ivy extracts are widely used in modern herbal medicines that are sold without prescription with a wide range of imputed benefits that include the amelioration of disorders of various internal organs, a topical treatment for burns and almost any other imaginable epidermal malady, and as an expectorant. The latter use is the most prevalent; in a 2007 study, it was reported that ivy extracts comprised 80 percent of all prescriptions for expectorants in Germany with over 2 million prescriptions costing about 13 million euros. In that iatrogenic consequence has been reported due to ivy consumption (remember it is poisonous), numerous studies have been instigated to evaluate its efficacy. Based on findings that Hedera helix was widely used for the dilation of bronchia, a 2011 study evaluated its effects on the stomach linings of rats; it caused them to contract. A systematic review of ten separate trials of ivy effectiveness for the treatment of upper respiratory tract infections (URTI) also in 2011 found that “although all studies report that ivy extracts are effective to reduce symptoms of URTI, there is no convincing evidence due to serious methodological flaws and lack of placebo controls.” This result is the Achilles’ heel of herbal medicine; double blind studies with adequate controls to lend scientific credence cost too much for a natural product that is already in mainstream use. Caveat emptor is the only viable approach to the herbal dilemma; there will never be proof, even if lambs eat it.