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Press Release: Invasive plant species are choking the Chicago region

How to help combat them during Illinois Invasive Species Awareness Month and beyond

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LISLE, Ill. (May 2, 2023)— Research shows that invasive trees and plants are wreaking havoc on ecosystems and yards in Illinois, and The Morton Arboretum is calling for help to eradicate them during Illinois Invasive Species Awareness Month in May.

The Arboretum’s 2020 Chicago Region Tree Census revealed that woody invasive plants represent more than 45% of Chicago-region trees. “Woody invasive species are a serious problem for the region,” said Lydia Scott, director of the Arboretum-led Chicago Region Trees Initiative (CRTI). “They spread aggressively, dramatically impacting our native habitats—in particular our oak ecosystems,” she added. For native, keystone species to thrive, Scott said that landowners, especially private landowners, should be aware of these species on their properties and take action to remove them and replace them with beneficial trees and shrubs.

The tree census identified European buckthorn (Rhamnus cathartica), Amur honeysuckle (Lonicera maackii), black locust (Robinia pseudoacacia), tree of heaven (Ailanthus altissima), Russian olive (Elaeagnus angustifolia), burning bush (Euonymus alatus) and Callery pear (Pyrus calleryana) as the most common invasives found in the Chicago region.

An aggressive spreader, buckthorn (European and glossy) alone makes up over one-third of the region’s trees, with most on private land, according to CRTI, a 200-plus partner organization working to improve the health of the regional forest. Buckthorn is a large shrub or tall tree with glossy green oval leaves. Dark blue or black berry-like fruits can be found in clusters on the female plants. Among other negative effects, buckthorn can change soil composition and make it difficult for other plants to grow in the future. Left unchecked in woodlands and yards, they can completely replace young trees and understory plants, including native wildflowers and other plants that form the basis of local ecosystems.

It can be a costly, time-consuming process to remove and manage invasive woody plants once they’ve proliferated. Buckthorn eradication efforts by local organizations have already cost millions annually, according to CRTI. The Morton Arboretum and CRTI do not recommend purchasing or planting invasive species. Those seeking non-invasive plant recommendations can visit the Arboretum’s online Tree Selector or contact its free Plant Clinic, which can help identify invasives either in person, by phone or by sending a photo via email.

Individuals, homeowners and land managers are being encouraged to help diminish invasive tree and plant species by removing existing invasives and selecting non-invasive trees and plants as replacements. Educational resources are available online through CRTI’s Invasive Species Hub and Healthy Habitats Series, and the Arboretum’s website.

Those wanting to help in the removal effort can sign up for volunteer opportunities through CRTI. The Arboretum also expects to open some new volunteer opportunities for invasive plant removal in June and July.

The Arboretum also is offering invasive species-related adult programs in May and throughout the year. They include New Invaders Watch Training Program (online) (free program on May 11); Plant Health Care Walking Tour (in person) (May 20 or June 10); Natural Areas Management (online and in person) (June 1, June 10 and June 17); Science and Stewardship of the Prairie (in person) (June 24); and Invasive Species (on demand) (anytime online).

Arboretum guests can also stop inside the Visitor Center from 11 a.m. to 2 p.m. Wednesdays and Saturdays in May for free information about potential invasive plants and insects and how to combat them.