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Bridge Gardens’ Weed of the Month | English ivy (Hedera helix)
By Rick Bogusch
Most of us know English ivy as the evergreen vine that clings to walls, tree trunks and other vertical surfaces or as a weed-suppressing ground cover in dense shade. Native to Europe and western Asia, and with a myriad of varieties, English ivy is a popular ornamental around the world, but it has been declared a “noxious weed” in Australia, New Zealand, Oregon and Washington and banned from sale.
Preferring moist, shady conditions with neutral or slightly acidic soils, English ivy does not do well in direct sunlight. It can easily climb 80 feet up a tree or spread 50 feet in many directions on the ground. Interestingly, it has 2 growth stages and 2 types of leaves. Most of us are familiar with the 5-lobed juvenile leaves that grow during the climbing or spreading stage. Mature leaves are oval in shape with no lobes and appear on flowering stems that grow out horizontally from the vines when they reach the crowns of trees or the tops of walls and cliffs.
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English ivy smothering trees in the woodland border
Flowers bloom in late summer. They are visually insignificant, small and greenish, but so numerous and so filled with nectar they are audibly noticeable from the ground below because of the hundreds of bees and other insects that visit for food. Clusters of blue-black fruits ripen in midwinter and are eaten and dispersed by birds and squirrels.
In its native range, English ivy is highly valued both as an ornamental and as an important food source for many species of insects, birds and other wildlife. In addition, it is often grown on building walls to provide insulation from summer’s heat and winter’s cold.
Outside its native range, growing English ivy is problematic. Spread by birds and small mammals, it easily escapes cultivation, outcompetes and displaces native vegetation and negatively affects the wildlife that depends on it. It can smother large and small trees, inhibit the growth of understory and on forest floors, create vast ivy “deserts,” where no other plants, native or not, can grow. Vines can add weight and wind resistance to tall trees and make them more susceptible to wind damage.
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Juvenile foliage of English ivy
Because it is so aggressively vigorous and can cover large areas, English ivy is tough to eradicate, even if you resort to chemical applications. Mechanical removal is effective but takes time. Vines on tree trunks can be cut at a 4-foot height and the lower portions pulled away from the tree’s base and then dug out. The upper portions will slowly die and look unsightly until the leaves drop off. Be careful not to damage tree roots when digging and pulling ivy vines from the ground.
Pulled vines often re-sprout and re-root if left on the ground. To dispose of ivy vines, it’s best to let them dry out on a hard, dry surface before tossing. Stems and roots left in the ground after pulling will also re-sprout, so it’s important to weed new growth regularly. Alternatively, cover areas after pulling vines with thick layers of cardboard and mulch to discourage regrowth.
There are hundreds of varieties of English ivy. There are plants with gold, white, grey-green or variegated leaves and most of them make good houseplants and container plants. Considering its invasiveness, perhaps this is best way to grow and enjoy English ivy.