Look out for plants that may be problems

Chicago Tribune

18-05-2025

The plants in our yards and gardens bring us beauty and joy, but some of them also bring problems.
'A plant can be a problem in a number of different ways,' said Sharon Yiesla, plant knowledge specialist in the Plant Clinic at The Morton Arboretum in Lisle. Many problem plants, mainly trees and shrubs, are called out in the plant information pages of the Arboretum's website (mortonarb.org/problem-plants).
'Before you plant anything, check it out to make sure you aren't bringing a danger or a high-maintenance headache to your yard,' she said.
We're all familiar with weeds, which take root easily and spread more aggressively than we'd like, and may go places we don't want them or outcompete other plants that we prefer. Some weeds listed on the Arboretum's website are such a problem that they are officially designated in Illinois as 'exotic weeds' or 'noxious weeds.'
Invasive plants are another major category. 'An invasive plant is more than just a plant that spreads easily,' Yiesla said. 'It's one that is not native to the area and whose presence negatively impacts, or is likely to impact, ecological, economic or human health.'
In natural areas such as forest preserves, national parks, and the Arboretum's restored prairies and woodlands, invasive plants choke out native species and are a major threat to the native ecosystems. May is designated as Invasive Species Awareness Month to call attention to this problem.
Exactly which plants are considered invasive varies from place to place, but the Midwest Invasive Plant Network (mipn.org) and the Invasive Plant Atlas of the United States (invasiveplantatlas.org) have detailed lists of invasive plants.
The Arboretum lists some plants as 'potentially invasive,' meaning that in its own woods, prairies, tree collections and garden, the plant has been observed spreading too readily. 'They are plants we are keeping an eye on, and it may pay to be wary of them,' Yiesla said.
Other trees and shrubs — including some that were once commonly planted in the Midwest — are not recommended by the Arboretum because they are too susceptible to extremely serious disease or insect problems.
One familiar example is ash trees, which are prey to the emerald ash borer. Another is Austrian pine, which is susceptible to diplodia tip blight, Zimmerman pine moth and other afflictions. 'Austrian pines used to be widely planted, even overplanted,' she said. 'Over several decades, as more and more problems cropped up and more of the trees died, it became clear that they just don't work here.'
A final category of problem plants is those that are dangerous because they cause skin irritations or are potentially toxic to handle or ingest. Poison ivy is a familiar example, but other dangerous plants include
pokeweed, poison hemlock, giant hogweed and stinging nettle.
The Arboretum's lists of problem plants and its recommendations are likely to shift over time, as more information becomes available and as new conditions emerge. 'Our weather will continue to change,' Yiesla said. 'That can lead to stress that makes many plants more susceptible to diseases and pests.'
The problem plant information pages can help careful gardeners choose plants that are likely to be beautiful, healthy and easy to care for. 'Thorough research is your best defense to make sure you don't plant a problem,' she said.