{"id":5467,"date":"2025-10-14T09:05:35","date_gmt":"2025-10-14T14:05:35","guid":{"rendered":"https:\/\/wp.stolaf.edu\/naturallands\/?page_id=5467"},"modified":"2025-10-21T12:27:49","modified_gmt":"2025-10-21T17:27:49","slug":"natural-lands-invasives-identification-guide-2","status":"publish","type":"page","link":"https:\/\/wp.stolaf.edu\/naturallands\/natural-lands-invasives-identification-guide-2\/","title":{"rendered":"Invasive Species of the Natural Lands"},"content":{"rendered":"
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Invasives<\/strong><\/h2>\n\n\n\n

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Invasive, noxious, non-native- what\u2019s the difference?<\/strong><\/h3>\n\n\n\n

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Invasive weeds are plants that dominate an ecosystem and spread rapidly once established, outcompeting native species, changing the composition of the habitat, and reducing overall biodiversity. According to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), invasive species play a role in 60% of global plant and animal extinctions.<\/p>\n\n\n\n

The term \u2018noxious\u2019 refers to a designation by a tribal, local, state, or federal authority of a plant as \u2018injurious to public health, agriculture, recreation, wildlife or property\u2019. The label allows land managers and owners to take action to curb or eradicate the species.<\/p>\n\n\n\n

\u2018Non-native\u2019 plants are plants from outside the given habitat; they are<\/em> often<\/em> invasive as they usually lack natural enemies and\/or barriers to acquiring resources in their habitat. They can be planted intentionally, as in ornamental use, or accidentally through transport. Following the “Ten Percent Rule”, 10% of a given amount of non-native species introduced to a new habitat will survive, and 10% of these survivors will dominate (thus 1% overall). However, those that do dominate inflict incredible damage. Nevertheless, not every introduced species will have selective advantages over native flora and fauna and may work quite amiably in the habitat. Likewise, some native species can be considered invasive if they reproduce aggressively, overtake resources, and\/or otherwise destabilize the ecosystem.<\/p>\n\n\n\n

Specially regulated species, such as the Amur maple, have unique restrictions. They may be native and hold economic value, such as in ornamental settings, but they present environmental concerns and require specific management plans.<\/p>\n\n\n\n

See below for a helpful graphic:<\/p>\n\n\n\n

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Invasives ID<\/strong><\/h2>\n\n\n\n

Below are our most common invasives. Note: unless you have experience in removing non-native species, please do not attempt to eradicate them yourself. Not only may you accidentally spread the seed, but you may injure yourself, as a number of invasives are irritable or even toxic.<\/p>\n\n\n\n

You can help expand this list by exploring the Natural Lands and adding observations to iNaturalist<\/a>.<\/p>\n\n\n\n

Click on each invasive below to learn more about them!<\/p>\n\n\n\n

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–> Garlic Mustard<\/strong> (Alliaria petiolata<\/em>)<\/summary>\n

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Photo Credit: Tony Atkin<\/a>, CC BY-SA 2.0<\/em><\/p>\n\n\n\n

Key characteristics:<\/strong> Coarsely toothed<\/strong>, kidney-shaped leaves (no more than 3 inches long and wide) that emit garlicky odor when crushed<\/strong>; flowering stalks have alternate, coarsely toothed leaves. Second year sees clusters of four-petaled white flowers<\/strong>. 1-2.5-inch slender seed pods contain a single row of many oval, black seeds.<\/p>\n\n\n\n

Habitat:<\/strong> Moist, shaded areas such as floodplain forests and deciduous woods, and along trails\/roads\/fences; can tolerate full sun<\/p>\n\n\n\n

Flowering Season:<\/strong> May-June<\/p>\n<\/details>\n\n\n\n

–> Birdsfoot Trefoil<\/strong> (Lotus corniculatus<\/em>)<\/summary>\n

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Photo Credit: Scot Magnotta<\/a>, CC BY-NC 4.0<\/em><\/p>\n\n\n\n

Key characteristics:<\/strong> Bright yellow flowers<\/strong> \u00bd-inch long with upper petal<\/strong> erect and rounded at tip<\/strong>, clustered in groups of 3-12; compound leaves in groups of three extending from a stalk as long as the leaflets; leaves are dark green, oval or oblong<\/strong>, toothless and usually hairless, and widest at or above middle with pointed tip, tapering to base, from which egg-shaped outgrowths (stipules)<\/strong> nearly as large as the leaflets grow.<\/p>\n\n\n\n

Habitat:<\/strong> Prairies and disturbed areas with full sun (often in ditches, waste areas, lawns, etc.); can adapt to a range of soil moistures<\/p>\n\n\n\n

Flowering Season:<\/strong> June-August<\/p>\n<\/details>\n\n\n\n

–> Spotted Knapweed<\/strong> (Centaurea stoebe<\/em>)<\/summary>\n

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Photo Credit: Matt Lavin<\/a>, CC BY-SA 2.0<\/em><\/p>\n\n\n\n

Key characteristics<\/strong>: Thistle-like pink to purple flower heads<\/strong>, with long, narrow ray flowers on the outside and disk flowers in the flower\u2019s center. Stems are stiff, hairy, and ridged<\/strong>. Leaves grow close to the ground in a clump in the first year and protrude as alternate, basal, gray-green to blue-green, deeply incised blades from the stem in the second year. Spotted Knapweed grows 2-3 feet tall<\/strong>.<\/p>\n\n\n\n

Habitat:<\/strong> Prefers dry, sandy soils and sun; common along edges of native prairie, forests, fields, gravel pits, roads, railways, trails, and other disturbed areas<\/p>\n\n\n\n

Flowering Season:<\/strong> June-October<\/p>\n<\/details>\n\n\n\n

–> Crown Vetch<\/strong> (Securigera varia<\/em>)<\/summary>\n

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Photo Credit: Peter Friedman<\/a><\/em>, CC BY-NC-SA 4.0<\/em><\/p>\n\n\n\n

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Key characteristics:<\/strong> Crown vetch flowers are composed of 1-inch round clusters (umbels) of 25 starburst-like light pink petals<\/strong>. Leaves are evenly compound<\/strong>, with 12 to 25 green leaflets, oval-shaped with a sharp point at the tip. Flower stalks are long and hairless. Stems are 2-6 feet long, low and spreading from base.<\/p>\n<\/div><\/div>\n\n\n\n

Habitat:<\/strong> Partial shade to full sun; along fields, woodlands, pastures, roads, prairies, dunes, and streambanks<\/p>\n\n\n\n

Flowering Season:<\/strong> May-September<\/p>\n<\/details>\n\n\n\n

–> Amur Maple<\/strong> (Acer ginnala<\/em>)<\/summary>\n

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Photo Credit: Daryl Mitchell<\/a> (left), Anonymous<\/a> (right), CC BY-SA 2.0<\/em><\/p>\n\n\n\n

Key characteristics:<\/strong> Simple opposite leaves are 3-lobed, palmate, and double-toothed<\/strong>, with the center lobe being much wider<\/strong> than the outside two. Leaves are dark green until fall, when they turn yellow or red. Branches are slender, grayish-brown, and smooth. Bark is moderately furrowed. Shrub grows 15-20 feet tall with a spreading, irregular crown<\/strong>. Fruit is a pair of 1 to 1 \u00bc inch samaras.<\/p>\n\n\n\n

Habitat:<\/strong> disturbed areas; urban and suburban landscapes; early successional forest, savanna, and open woodlands; tolerates full sun to partial shade and a range of soil moisture levels<\/p>\n\n\n\n

Flowering Season:<\/strong> April-May<\/p>\n<\/details>\n\n\n\n

–> White Sweet Clover<\/strong> (Melilotus albus<\/em>)<\/summary>\n

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Photo Credits: Frank Mayfield<\/a> (left) and Christophe Bornand<\/a> (right)<\/em><\/p>\n\n\n\n

Key characteristics:<\/strong> May grow tall and lanky or squat and bushy. Oblong gray-green leaves<\/strong>, rounded in the middle and wedge-shaped at the base, grow in groups of 3<\/strong>, sparsely distributed along stems. Leaves are slightly toothed and hairless. Middle leaflet has its own petiole. At the base of each leaf stalk is a pair of stipules (appendages) 3\/8-inch long. Spike-like racemes of white flowers<\/strong> grow densely along branching stems. Stems are hairless and often ridged. Individual flowers are 1\/4 inch long, pea-like, and drooping<\/strong>. Fruit is an oval pod with very short veins<\/strong> and 1-2 seeds.<\/p>\n\n\n\n

Habitat:<\/strong> Open, sunny, disturbed areas with dry to moist soil such as roadsides, railroads, gravel pits, old fields, weedy meadows; also, prairies, shores, river banks, and woodland edges<\/p>\n\n\n\n

Flowering Season:<\/strong> June-October<\/p>\n<\/details>\n\n\n\n

–> Yellow Sweet Clover<\/strong> (Melilotus officinalis<\/em>)<\/summary>\n

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Photo Credits: Anita Gould<\/a> (left) and Peter Friedman<\/a> (right)<\/em>, CC BY-NC 4.0<\/a><\/em><\/p>\n\n\n\n

Key characteristics:<\/strong> May grow tall and lanky or squat and bushy. Alternate, gray-green leaves grow in groups of 3<\/strong> and are diamond-shaped to lance-oblong<\/strong>, rounded in the middle and wedge-shaped at the base. Leaves are slightly toothed and hairless. Stems are hairless and often ridged. At the base of each leaf stalk is a pair of stipules (appendages) 3\/8-inch long. Middle leaflet has its own petiole. Spike-like racemes of yellow flowers <\/strong>grow densely along branching stems; individual flowers are 1\/4 inch long, pea-like, and drooping<\/strong>. Fruit is an oval pod with irregular, elongated veins<\/strong> and 1-2 seeds.<\/p>\n\n\n\n

Habitat:<\/strong> Full or partial sun on disturbed, heavy soil; moist to mesic conditions; old fields, prairies, roadsides, railroads, gravel pits, weedy meadows, vacant lots, shores, river banks, woodland edges. Also thrives in high-quality habitat and in fire-affected settings.<\/p>\n\n\n\n

Flowering Season:<\/strong> June-September<\/p>\n<\/details>\n\n\n\n

–> Erect Hedge Parsley <\/strong>(Torilis japonica)<\/em><\/summary>\n

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Photo Credits: Janet Elliott<\/a> (right), Aleksander Levon<\/a> (left)<\/em>, CC-BY-NC<\/em><\/p>\n\n\n\n

Key characteristics: <\/strong>Erect Hedge Parsley (a.k.a Japanese Hedge Parsley) is a 2-6 foot tall biennial. The plant\u2019s first-year low-growing rosette stays green through late fall. Once it flowers, it sports 1.5-2 inch umbels<\/strong>, each with a few, small, narrow bracts at base<\/strong>. On these umbels cluster \u215b-in-wide white flowers<\/strong> with 5 notched petals of unequal size<\/strong> and a pink-tinged stem. 5-inch-long alternately attached compound leaves <\/strong>with stiff white hairs<\/strong> grow in groups of 3-5. They are feathery and deeply divided<\/strong>, except near the very tip of each leaf. Stems are erect and ridged. Erect Hedge Parsley has bristly brown fruit<\/strong> with little hooked hairs<\/strong>. The plant is very open early in the season but becomes more branched as it matures.<\/p>\n\n\n\n

Habitat: <\/strong>Open woodlands, hedge rows, roadsides, and waste sites in addition to degraded or high-quality grasslands; withstands full sun, partial shade, and full shade<\/p>\n\n\n\n

Flowering Season: <\/strong>July-August<\/p>\n<\/details>\n\n\n\n

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Can you tell the difference?<\/strong><\/h2>\n\n\n\n

Below are our invasives that have a common non-invasive look-alike. <\/strong>Click on each comparison to learn more about them!<\/p>\n\n\n\n

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<\/strong>+KEY HERE<\/strong>:<\/summary>\n

Red= INVASIVE: REMOVE<\/mark><\/strong><\/p>\n\n\n\n

Black= KEEP<\/strong><\/p>\n\n\n\n

Purple= TOXIC (MAY OR MAY NOT REMOVE)<\/mark><\/strong><\/p>\n<\/details>\n<\/div>\n\n\n\n

–> Creeping Bellflower<\/strong> <\/mark>vs American Bellflower<\/mark><\/strong><\/summary>\n

Creeping Bellflower (Campanula rapunculoides<\/em>) vs American Bellflower (Campanulastrum americanum)<\/em><\/mark><\/p>\n\n\n\n