How to Identify, Grow, and Control Irish Ivy

Irish ivy (Hedera hibernica) is a familiar evergreen vine, recognized for its vigorous growth and lush, dark green foliage. It is frequently used in landscaping to create dense ground cover, conceal unsightly areas, or climb walls for a classic, established look. The plant’s adaptability and low maintenance needs have also made it a popular choice for indoor cultivation, where its trailing stems are valued in hanging baskets and containers.

Identifying Irish Ivy

Distinguishing Irish ivy from its close relative, English ivy (Hedera helix), requires observing a few key characteristics. Irish ivy leaves are broader and larger than English ivy’s, often reaching 10 centimeters wide. The leaves have five lobes with a wide central lobe, and the surface is a uniform dark green with veins that are not prominently raised or silvery.

A more definitive method is examining the tiny hairs, or trichomes, on the underside of new leaves with a magnifying glass. On Irish ivy, these trichomes are flattened and lie parallel to the leaf surface. In contrast, English ivy’s trichomes are bristly and stand erect. Another clue is the scent; crushed Irish ivy leaves have a sweet or resinous aroma, while English ivy smells musty.

Irish Ivy Care Guide

Irish ivy is tolerant of a wide range of conditions, making it adaptable for gardens and homes. It performs best in partial to full shade outdoors or bright, indirect light indoors, as direct sun can scorch its leaves. The plant thrives in well-draining soil and should be watered after the top inch of soil has dried out to prevent root rot. While newly planted ivy requires regular watering, mature plants are quite drought-tolerant.

During the spring and summer growing season, apply a balanced, water-soluble fertilizer every four to six weeks to encourage healthy foliage. Houseplants may need repotting every two to three years if they become root-bound. To maintain a desired shape and encourage denser growth, prune the vines in late winter or early spring before new growth begins.

Invasiveness and Potential Problems

The vigor that makes Irish ivy a popular garden plant also makes it an invasive species in regions like the Pacific Northwest of North America and New Zealand. When it escapes cultivation, it forms dense, sprawling mats across forest floors. These “ivy deserts” block sunlight and outcompete native grasses and wildflowers for water and nutrients, which severely reduces local biodiversity.

Its climbing habit poses a direct threat to trees. The ivy adds significant weight to the canopy, making trees more susceptible to breaking in storms. Its dense foliage can also envelop a tree’s leaves, blocking light needed for photosynthesis and weakening the host. This aggressive growth can also damage building facades and fences by working into mortar and woodwork, leading to its classification as a noxious weed in some regions.

Irish ivy is also toxic to humans, cats, and dogs. The leaves and berries contain triterpenoid saponins, which can cause vomiting, abdominal pain, and diarrhea if ingested. The plant’s sap can also cause skin irritation or allergic contact dermatitis in sensitive individuals who handle it without gloves.

Controlling and Removing Irish Ivy

To control Irish ivy’s spread in a landscape, regular pruning is necessary. Trim the edges of a groundcover patch at least once a year to prevent it from creeping into unwanted areas. If the ivy is grown as a climber, keep it pruned away from valuable trees, building eaves, and woodwork to prevent damage.

For ivy that has begun to climb a tree, creating a “survival ring” is an effective control method. This involves cutting all ivy vines around the tree’s trunk at both waist and ankle height and removing the section of vines between the cuts. This severs the vine from its roots, causing the upper portions to die without damaging the tree’s bark. Clearing a three- to six-foot radius on the ground around the tree’s base prevents it from quickly re-establishing.

Complete eradication requires removing the entire plant, including all root fragments, as even small pieces can resprout. Manual removal is easiest when the soil is moist. For large mats, the “ivy roll” technique can be used by cutting the mat into strips and rolling it up like a carpet. An alternative is sheet mulching, which involves covering the ivy with cardboard and mulch to block sunlight for up to two years. Disposed of removed ivy carefully by letting it dry on a tarp or in sealed bags, as fresh cuttings can re-root in compost.