Invasive Species
When plants are introduced to a new location, either intentionally or accidentally, they can spread prolifically, out-compete native species for resources, and eventually even dominate the landscape. Biologists are studying the mechanisms underlying a taxon’s ability to become invasive, but it can be difficult to predict whether or not a species will become invasive in a new habitat. With an increased awareness about the environmental and economic threats posed by invasive species, the ºÚÁϳԹÏÍø has expanded and strengthened its invasive plant policy. We also partner with other gardens to be part of an invasive plant sentinel network, sharing information about plant species we see spreading.
ºÚÁϳԹÏÍø Status:
| R | Remove as soon as possible, including all cultivars, and/or do not add to collection in future |
| P | Phase out (species that pose a lesser invasive risk, form significant structural features in landscape, and will be time-consuming to replace will be phased out over a five- to ten-year period) |
| E | Evaluate species and cultivars, then remove invasive taxa |
| W | Watch and monitor for signs of invasiveness |
| Scientific Name Common Name | Plan | Removal complete? |
| Acer ginnala Amur maple | P | Underway |
| Acer platanoides Norway maple | R | 2015 |
| Aegopodium podagraria Goutweed | R | 2005 |
| Agropyron repens Quack grass | R | * |
| Ailanthus altissima Tree-of-heaven | R | |
| Alliaria petiolata Garlic mustard | R | * |
| Alnus glutinosa European black alder | P | 2024 |
| Alternanthera philoxeroides Alligator weed | R | |
| Ampelopsis brevipedunculata Porcelainberry vine | R | 2003 |
| Anthriscus sylvestris Wild chervil | R | |
| Arctium minus Lesser burdock | R | * |
| Artemisia absinthium Wormwood | R | |
| Artemisia vulgaris Mugwort | R | |
| Azolla spp. Water fern | R | |
| Berberis thunbergii Japanese barberry | R | 2017 |
| Berberis koreana Korean barberry | R | 2019 |
| Berberis koreana x B. thunbergii (incl. 'Tara' cv.) Hybrid barberry | R | 2019 |
| Berberis vulgaris European barberry | R | |
| Bromus inermis Smooth brome | R | |
| Butomus umbellatus Flowering rush | R | |
| Cabomba caroliniana Fanwort | R | * |
| Calamagrostis brachytricha Reed grass | R | Underway |
| Carduus nutans Nodding plumeless thistle | R | * |
| Carex divulsa | R | |
| Celastrus orbiculatus Oriental bittersweet | R | 2003 |
| Centaurea maculosa Spotted knapweed | R | |
| Cirsium arvense Canada thistle | R | * |
| Cirsium palustre Marsh plume thistle | R | * |
| Cirsium vulgare Bull thistle | R | * |
| Conium maculatum Poison hemlock | R | * |
| Coronilla varia Crown vetch | R | 2005 |
| Cotoneaster multiflorus Many-flowered cotoneaster | P | |
| Daucus carota Queen Anne's lace | R | * |
| Dioscorea batatas Chinese yam | R | 2005 |
| Dipsacus laciniatus Cutleaf teasel | R | * |
| Dipsacus sylvestris Teasel | R | * |
| Duchesnia indica Wild strawberry | R | 2004 |
| Echinops sphaerocephalus Globe thistle | R | |
| Egeria densa Brazilian elodea | R | |
| Eichornia crassipes Water hyacinth | R | |
| Elaeagnus umbellatus Autumn olive | R | |
| Epilobium hirsutum Hairy fireweed | R | |
| Euonymus alatus Winged euonymus | R | |
| Euonymus europeaus European spindletree | R | 2005 |
| Euonymus fortunei Wintercreeper | R | Underway |
| Euphorbia cyparissias Cypress spurge | R | |
| Euphorbia esula Leafy spurge | R | |
| Festuca elatior (=F. arundinacea) Tall fescue | R | * |
| Festuca pratense Meadow fescue | R | |
| Glechoma hederacea Ground ivy | R | * |
| Hemerocallis fulva (locally invasive) Tawny daylily | R (wild type only) | |
| Heracleum mantegazzianum Giant hogweed | R | |
| Hesperis matronalis Dame's rocket | R | 2005 |
| Hippophae rhamnoides Common sea buckthorn | R | * |
| Hydrilla verticillata Hydrilla, water thyme | R | * |
| Hydrocharis morsus-ranae European frog-bit | R | |
| Hypericum perforatum Common St. Johnswort | R | 2004 |
| Inula helenium Horse-heal | R | |
| Ipomoea aquatica Water spinach | R | |
| Iris pseudacorus Yellow flag iris | R | 2005 |
| Lapsana communis Nipplewort | R | |
| Lespedeza cuneata Chinese bush clover | R | |
| Leymus arenarius Blue lyme grass | R | |
| Ligustrum obtusifolium Border privet | P | |
| Ligustrum vulgare Common privet | P | |
| Linaria vulgaris Butter-and-eggs | R | 2005 |
| Lonicera x bella Bell's honeysuckle | R | |
| Lonicera japonica Japanese honeysuckle | R | 2003 |
| Lonicera maackii Amur honeysuckle | R | |
| Lonicera morrowii Morrow's honeysuckle | R | |
| Lonicera tatarica Tatarian honeysuckle | R | * |
| Lotus corniculatus Bird's-foot trefoil | R | * |
| Lysimachia nummularia Moneywort | R | 2003 |
| Lysimachia verticillata Whorled loosestrife | R | |
| Lythrum salicaria Purple loosestrife | R | * |
| Malus spp. (crabapples) Crabapple | E, I | |
| Melilotus alba White sweet-clover | R | |
| Melilotus officinalis Yellow sweet- clover | R | |
| Microstegium vimineum Japanese stilt grass | R | |
| Miscanthus sacchariflorus Amur silver grass | R | |
| Miscanthus sinensis Chinese silver grass, Autumn Red Miscanthus, Flame Grass, Eulalia, Maiden Grass, Zebra Grass | R (exempted cultivars are M.s. ‘Silberpfeil,’ ‘Hinjo’ and Miscanthus x giganteus) | 2016 |
| Morus alba Mulberry | P | |
| Myriophyllum aquaticum Parrot feather | R | * |
| Myriophyllum spicatum Eurasian watermilfoil | R | * |
| Najus minor Toothed water weed | R | * |
| Nasturtium officinale Watercress | R | |
| Nymphoides peltata Yellow floatingheart | R | |
| Pastinaca sativa Wild parsnip | R | |
| Pennisetum alopecuroides Chinese fountain grass | R | Underway |
| Perilla frutescens Beefsteak plant | R | |
| Phalaris arundinacea Reed canary grass | R | 2004 |
| Phellodendron amurense (excluding male cultivars) Amur corktree | R | |
| Phellodendron japonica (excluding male cultivars) Japanese corktree | R | |
| Phragmites australis Common reed | R | |
| Pistia stratiotes Water lettuce | R | |
| Poa compressa Canada bluegrass | I | |
| Poa pratensis Kentucky bluegrass | I | |
| Polygonum cuspidatum = P. japonicum Japanese knotweed | R | |
| Polygonum perfoliatum Asiatic tearthumb | R | |
| Polygonum sachalinense Giant knotweed | R | |
| Populus alba White poplar | P | |
| Portulaca oleracea Purslane | R | |
| Potamogeton crispus Curlyleaf pondweed | R | * |
| Potentilla argentea Silver cinquefoil | R | |
| Prunus mahaleb Mahaleb cherry | P | |
| Pueraria montana =P. lobata Kudzu vine | R | * |
| Pyrus calleryana Callery pear | R | 2019 |
| Ranunculus ficaria Lesser celendine | R | |
| Rhamnus cathartica Common buckthorn | R | * |
| Rhamnus frangula Glossy buckthorn | R | 2005 |
| Robinia pseudoacacia (native to N. Am.; aggressive in our region) Black locust | R wild type; E cultivars | 2004 |
| Rorippa sylvestris Creeping yellow-cress | R | |
| Rosa canina | R | |
| Rosa multiflora Japanese rose | R (check rootstocks) | * |
| Rumex acetosella Garden sorrel | R | * |
| Salvinia molesta and S.minima Water fern | R | * |
| Saponaria officinalis Bouncing bet | R | 2005 |
| Setaria faberi Japanese bristlegrass | R | |
| Silene latifolia ssp. alba (Lychnis alba) White campion | R | |
| Sonchus arvensis Field sow thistle | R | * |
| Sorghum halapense Johnson grass | R | |
| Stachys balansae No common name | R | |
| Symphytum asperum Prickly comfrey | R | |
| Thalictrum buschianum No common name | R | |
| Trapa natans European water chestnut | R | * |
| Typha angustifolia Narrow leaf cattail | R | |
| Ulmus pumila Siberian elm | R | |
| Valeriana officinalis Common valerian | R | 2005 |
| Verbascum thapsus Flannel mullein | R | * |
| Veronica gentianoides Gentian speedwell | R | |
| Viburnum opulus European cranberrybush viburnum | R | |
| Vinca minor Common periwinkle | E, I | |
| Vincetoxicum nigrum Black swallowwort | R | * |
| Vincetoxicum rossicum Swallowwort | R | * |
Watch List
These taxa are not currently posing a serious invasive risk in the Chicago area, but may do so in the future, particularly as the climate changes. Plan: W= watch and monitor for signs of invasiveness. Addition of Watch List taxa to the collection should be avoided.
| Scientific Name Common Name | Plan |
| Akebia quinata | W |
| Buddleja davidii | W |
| Elaeagnus angustifolia | W |
| Gypsophila paniculata | W |
| Houttuynia cordata | W |
| Quercus acutissima | W |
| Ranunculus acris | W |
| Ranunculus lingua | W |
| Scilla siberica | W |
| Spiraea japonica | W |
| Syringa reticulata | W |
| Tamarix ramosissima and other Tamarix spp. | W |
| Verbina bonariensis | W and deadhead |
| Wisteria sinensis | W |