English Ivy (Hedera helix) is a classic evergreen vine, often used in landscaping for its dense, shade-tolerant foliage and its ability to quickly cover walls or serve as a thick ground cover. However, its vigorous growth habits have led to significant ecological concern in various regions of the United States. In Colorado, while not always regulated at the highest state level, this species is increasingly viewed as a damaging, non-native invader that requires active management.
Official Status as an Invasive Species in Colorado
English Ivy does not appear on the official Colorado state-mandated Noxious Weed List, which categorizes plants for mandatory management under the Colorado Noxious Weed Act. Despite this absence from the statewide mandate, Hedera helix is still widely recognized as an invasive, non-native plant by local Colorado municipalities, conservation groups, and gardening resources. Many regional and county-level weed management programs include it on their local lists due to its aggressive growth and destructive nature in the temperate climate zones along the Front Range.
English Ivy poses a severe ecological threat to native Colorado vegetation and urban trees. It grows both horizontally as a dense ground cover and vertically as a climber, forming thick mats that effectively smother native wildflowers and seedlings by monopolizing sunlight and nutrients. When the vine climbs up a tree trunk, it develops thick, woody stems that can envelop the canopy, blocking the host tree’s leaves from performing photosynthesis. This gradual process can lead to the decline and eventual death of mature trees over several years.
Beyond shading, the sheer weight of the ivy, especially when wet or covered in snow, significantly stresses the tree’s structure and increases its susceptibility to windthrow during storms. The vine attaches itself to surfaces using small, root-like structures called adventitious roots that adhere firmly to bark or masonry. This tight grip can also harbor insect pests and moisture, making the host tree more vulnerable to diseases and decay.
Identifying the Plant and Toxicity Risks
English Ivy exhibits two distinct growth phases with different leaf shapes. The most common form seen in gardens is the juvenile phase, characterized by dark green, waxy, three- to five-lobed leaves. As the vine matures and begins to climb vertically, it transitions into the adult phase, producing unlobed, oval-shaped leaves, flowers, and fruit.
The plant contains toxic compounds known as triterpenoid saponins, which are concentrated in the leaves and, most significantly, in the small, dark purple or black berries. Ingestion of these plant parts can cause a range of unpleasant symptoms in humans and pets, particularly dogs and cats. Common reactions include severe gastrointestinal distress, such as vomiting, diarrhea, and abdominal pain.
In severe cases, the toxic saponins can lead to more serious neurological symptoms like delirium, excitability, or convulsions, necessitating immediate medical or veterinary intervention. Beyond ingestion, the plant sap contains falcarinol, a compound that can cause contact dermatitis upon skin exposure. Handling the vine without gloves can lead to skin irritation, redness, and blistering, which should be managed by washing the affected area thoroughly with soap and water.
Effective Removal and Disposal Methods
The first step for ivy climbing a tree is to sever the main woody vines at the base of the trunk, cutting a three-foot section out to break the connection between the roots and the upper foliage. It is important to leave the upper portion of the vine attached to the tree bark, as attempting to pull it down can severely strip the bark and cause irreparable damage to the tree.
For ground cover, manual removal is the most effective long-term strategy, especially in areas where native plants are present. The thick mats of ivy must be peeled back and dug up, taking care to remove all the runners and shallow root systems, which can be quite extensive. A heavy-duty garden rake or specialized hoe can be used to loosen the dense matting, making it easier to roll up and remove from the soil. Because the vine can regenerate from even small stem fragments, continuous monitoring and follow-up removal of new sprouts are necessary for successful eradication.
Chemical treatments are an option for dense, widespread ground infestations, typically involving a systemic herbicide with an active ingredient such as glyphosate. However, the thick, waxy coating on the leaves makes them naturally resistant to herbicide absorption, often requiring the leaves to be scored or crushed before application to allow the chemical to penetrate the plant tissue. Application must be done with extreme care to avoid drift, which can easily damage or kill desirable native trees and plants in the surrounding area.
English Ivy should never be placed in a compost pile, as the stems and runners have the capacity to root and grow even after being pulled from the soil. All removed plant material, particularly any cuttings or berries, must be bagged securely in heavy-duty plastic trash bags and disposed of through a municipal waste service or taken to a landfill. Allowing the pulled material to dry out completely on a hard surface or tarp for several weeks before bagging helps ensure the fragments are dead and incapable of re-rooting.