On 08 May 2009 20:42:09 GMT, wrote:
http://www.nps.gov/plants/ALIEN/fact/hehe1.htm
http://www.portlandonline.com/parks/?c=47820
"ECOLOGICAL THREAT
English ivy is a vigorous growing vine that impacts all levels of disturbed and
undisturbed forested areas, growing both as a ground cover and a climbing vine. As
the ivy climbs in search of increased light, it engulfs and kills branches by
blocking light from reaching the host tree’s leaves. Branch dieback proceeds from the
lower to upper branches, often leaving the tree with just a small green “broccoli
head.” The host tree eventually succumbs entirely from this insidious and steady
weakening. In addition, the added weight of the vines makes infested trees much more
susceptible to blow-over during high rain and wind events and heavy snowfalls. Trees
heavily draped with ivy can be hazardous if near roads, walkways, homes and other
peopled areas. On the ground, English ivy forms dense and extensive monocultures that
exclude native plants. English ivy also serves as a reservoir for Bacterial Leaf
Scorch (Xylella fastidiosa), a plant pathogen that is harmful to elms, oaks, maples
and other native plants."