Inglese

Destructive ivy (INTERMEDIATE LEVEL)

Q. Is English ivy destructive and dangerous to trees and houses? Even if it *pulls off a little *bark, or some *mortar, are bricks unaffected? Or does it destroy *masonry and sap the life out of a living tree?

A. Slowly but surely both the tree and the building will be sorry they couldn’t move to get out of the way. Ivy won’t pull off tree bark unless you try to remove it by brute force, but as it spreads upward and throughout the *canopy, it *shades out the tree’s inner leaves. None of those leaves are there just for decoration – the tree needs ail the food they can make. A trunk covered by ivy can also make it hard to see structural damage from other sources. It isn’t that ivy attacks in the way that twining vines can strangle a tree; ivy does its damage *inadvertently. You and I may think ivy is beautiful on buildings, but the Ivy League grounds and buildings managers at Harvard and Yale agree it’s a problem. Ivy grows small *rootlets, appropriately called holdfasts, which make a glue that dissolves some of the mortar between bricks. Worse, the ivy *traps moisture, dust and *debris next to the building. Between acid rain and the decomposition of the debris, the acidity next to the building increases. That causes further damage to mortar as the carbonates in it dissolve. All buildings with mortar eventually need re- pointing, replacing worn mortar. Ivy makes it happen sooner. Parthenocissus tricuspidata, commonly called Boston ivy because it was used to cover Harvard’s brick buildings, is at least deciduous. In the winter, snow and ice could drop off and the walls could *dry out.

(da nytimes.com)

VOCABULARY

to pull off: to remove forcefully; to succeed in performing (a difficult feat)

bark: a protective layer of dead corky cells on the outside of the stems of woody plants

mortar: a mixture of cement or lime or both with sand and water, used as a bond between bricks or stones

masonry: work that is built by a mason; stonework or brickwork

canopy: the highest level of branches and foliage in a forest, formed by the crowns of the trees

to shade out: to screen or protect from heat, light, view, etc.

inadvertently: unintentionally; inattentively

rootlet: a small root or branch of a root

to trap: to take, catch or pen in a trap; entrap

debris: fragments or remnants of something destroyed or broken; rubble