Common Invasive Species in Northern Indiana

Why Invasive Species Are a Problem in Northern Indiana

Invasive plant species are non-native plants that spread aggressively, crowd out native vegetation, and damage the ecosystems they colonize. In Northern Indiana, several invasive species have become so widespread that they dominate fence rows, forest edges, abandoned farmland, and neglected properties across the region.

The problem is not just ecological. Invasive species reduce property usability, block fence lines, hide property boundaries, and make land difficult to manage. A fence row that was clean 10 years ago can become an impenetrable wall of bush honeysuckle. A wooded lot that had a healthy native understory can be taken over by autumn olive until nothing else grows beneath the canopy.

For landowners in Northern Indiana, invasive species are a practical problem as much as an environmental one. Removing them restores access, usability, and value to the property — and prevents further spread to neighboring land.

Here are the most common invasive species you will encounter across the Northern Indiana landscape.

Bush Honeysuckle

Bush honeysuckle is the single most common invasive shrub in Northern Indiana. Three species — Amur honeysuckle, Morrow's honeysuckle, and Tartarian honeysuckle — have spread across the state and are present on a large percentage of rural and suburban properties.

How to identify it

Bush honeysuckle is a multi-stemmed shrub that typically grows 6 to 15 feet tall. It has opposite leaves (two leaves at each node), tubular white or pink flowers in spring, and red or orange berries in fall. One of its most distinctive features is that it leafs out earlier in spring and holds its leaves later in fall than native shrubs — so it is often the only green shrub in a woodland in early April or late November.

Where it grows

Fence rows, forest edges, woodland understory, roadsides, field margins, and any disturbed or semi-shaded area. It thrives in partial shade but also tolerates full sun. In Northern Indiana, it is particularly dense along fence rows between agricultural fields and in the understory of second-growth woodlands.

Why it is a problem

Bush honeysuckle forms dense thickets that shade out native wildflowers, tree seedlings, and understory plants. It leafs out early and drops leaves late, giving it a competitive advantage over native species. Birds eat the berries and spread seeds widely, so even a few plants can colonize a large area within a few years. Dense stands make fence rows impassable, hide property boundaries, and provide poor habitat compared to native vegetation.

How to remove it

Small plants (under 1 inch stem diameter) can be pulled by hand when the soil is moist. Larger plants should be cut at the base with loppers or a chainsaw and the fresh stump immediately treated with a herbicide containing triclopyr or glyphosate to prevent regrowth. For large infestations — which is the norm in Northern Indiana — forestry mulching clears dense honeysuckle stands efficiently. A mulcher can process acres of honeysuckle in a single day that would take weeks to cut by hand.

Autumn Olive

Autumn olive is a large invasive shrub or small tree that was widely planted in Indiana through the mid-20th century for wildlife habitat and erosion control — before its invasive nature was understood. It is now one of the most common invasive plants in the state.

How to identify it

Autumn olive grows 10 to 20 feet tall as a multi-stemmed shrub or small tree. Its leaves are oval with a distinctive silvery-white underside that makes the plant easy to spot, especially when the wind flips the leaves. It produces small, fragrant yellowish flowers in spring and abundant small red berries with silver speckles in fall.

Where it grows

Old fields, pasture edges, roadsides, fence rows, and open to semi-open areas. It tolerates poor soils and drought well. It was intentionally planted along highways and on reclaimed land throughout Indiana, and it has since spread far beyond those original plantings.

Why it is a problem

Autumn olive fixes nitrogen in the soil, which sounds like a benefit but actually changes soil chemistry in ways that favor other invasive species over native plants. It produces enormous quantities of berries — a single plant can produce tens of thousands of seeds per year — and birds spread them across the landscape. Dense stands shade out native prairie grasses and wildflowers and can dominate entire fields.

How to remove it

Cut-stump treatment with triclopyr is the most reliable method for individual plants. Cut the stem as close to the ground as possible and apply herbicide to the fresh cut within 15 minutes. For large stands, forestry mulching followed by spot-treatment of any resprouting stumps is the most efficient approach. Autumn olive resprouts aggressively from the root system, so follow-up monitoring is important.

Multiflora Rose

Multiflora rose is a thorny, arching shrub that forms impenetrable thickets. Like autumn olive, it was widely planted in Indiana as a living fence and for erosion control before being recognized as invasive.

How to identify it

Multiflora rose has arching, thorny canes that can grow 10 to 15 feet long. Its leaves are compound with 5 to 11 small, serrated leaflets. It produces clusters of small white flowers in late spring and small red rose hips in fall and winter. The fringed stipules (small leaf-like structures at the base of each leaf stalk) distinguish it from native roses.

Where it grows

Fence rows, pasture edges, forest openings, roadsides, and disturbed areas. In Northern Indiana, multiflora rose is especially common in old fence rows and at the edges of grazed pastures where cattle avoid the thorns.

Why it is a problem

Multiflora rose forms dense, thorny thickets that are nearly impossible to walk through. It overtakes fence rows, making fence maintenance impossible without first removing the rose. Birds spread seeds widely, and the plant also spreads by root layering — where arching canes touch the ground, they root and produce new plants.

How to remove it

Hand removal is painful and slow due to the thorns. Repeated mowing can weaken stands over several seasons but rarely eliminates them. Forestry mulching handles multiflora rose efficiently, grinding through the thorny canes and root crowns. Herbicide treatment of cut stumps with triclopyr helps prevent regrowth. For large infestations, mulching is by far the most practical removal method.

Tree of Heaven (Ailanthus)

Tree of heaven is a fast-growing invasive tree that can reach 60 to 80 feet tall. It is increasingly common in Northern Indiana, particularly in urban areas, along roadsides, and on disturbed land.

How to identify it

Tree of heaven has large compound leaves with 10 to 40 leaflets, each with a small notch at the base and a distinctive glandular bump. The bark is smooth and gray on young trees, becoming lightly furrowed on older specimens. Crushed leaves and stems have a strong, unpleasant odor often described as rancid peanut butter. It produces large clusters of papery, winged seeds that hang on the tree into winter.

Where it grows

Roadsides, railroad corridors, urban lots, disturbed land, and forest edges. It is extremely tolerant of poor soil, pollution, and drought. In Northern Indiana, it is most common in and around towns and along transportation corridors, but it is spreading into rural areas.

Why it is a problem

Tree of heaven grows extremely fast — up to 6 feet per year — and produces chemicals in its leaves, bark, and roots that inhibit the growth of other plants (a process called allelopathy). A single female tree can produce 300,000 or more seeds per year. When cut, it resprouts aggressively from the stump and sends up root suckers that can emerge 50 feet or more from the parent tree. It is also the preferred host for the spotted lanternfly, an invasive insect that threatens agriculture.

How to remove it

Cutting tree of heaven without herbicide treatment will make the problem worse — the tree responds to cutting by sending up dozens of root suckers. The recommended approach is the "hack and squirt" method: make downward cuts into the bark around the trunk and apply triclopyr or imazapyr into the cuts. This kills the root system and prevents suckering. For stands with multiple trees, forestry mulching combined with follow-up herbicide treatment on resprouts is effective.

Callery Pear (Bradford Pear)

Callery pear — commonly known as Bradford pear — was one of the most popular ornamental trees in the Midwest for decades. It is now recognized as highly invasive and is spreading rapidly across Indiana.

How to identify it

Callery pear grows 30 to 50 feet tall with a rounded or oval crown. It is one of the first trees to bloom in spring, producing masses of white flowers with an unpleasant fishy odor. Leaves are glossy, dark green, and round with scalloped edges. Wild Callery pears (as opposed to nursery cultivars) often have thorns up to 3 inches long. Fall foliage ranges from purple to red.

Where it grows

Roadsides, field edges, old pastures, highway medians, and any open or semi-open area. It spreads rapidly from ornamental plantings in nearby neighborhoods. In Northern Indiana, it is increasingly visible along highways and at the edges of agricultural fields.

Why it is a problem

Callery pear produces abundant fruit eaten by birds, who spread seeds across the landscape. Wild seedlings are thornier and more aggressive than nursery cultivars. Dense stands form in open areas, shading out native grasses and wildflowers. Indiana banned the sale of Callery pear trees starting in 2023, but existing trees and established populations continue to spread.

How to remove it

Small seedlings can be pulled by hand. Larger trees should be cut and stumps treated with triclopyr to prevent resprouting. Forestry mulching handles stands of Callery pear efficiently, though larger specimens (over 8 to 10 inches) may need to be felled with a chainsaw first. Like tree of heaven, cut-stump herbicide treatment is important to prevent regrowth.

Japanese Knotweed

Japanese knotweed is an aggressive perennial plant that spreads by underground rhizomes and is extremely difficult to eradicate once established.

How to identify it

Japanese knotweed grows 6 to 10 feet tall with thick, bamboo-like stems that are hollow and have visible joints. Leaves are large (3 to 6 inches), broadly oval, and come to an abrupt point. Small white flower clusters appear in late summer. In winter, the dead canes remain standing and are a distinctive reddish-brown color.

Where it grows

Stream banks, roadsides, vacant lots, and disturbed areas. It tolerates a wide range of conditions but is especially common near water. In Northern Indiana, it is found along rivers, drainage ditches, and in older residential areas where it was sometimes planted as an ornamental screen.

Why it is a problem

Japanese knotweed spreads primarily through its rhizome system, which can extend 20 feet or more from the visible plant and penetrate through asphalt, concrete, and building foundations. A fragment of rhizome as small as half an inch can produce a new plant. Dense stands completely exclude native vegetation and are nearly impossible to remove without sustained, multi-year effort.

How to remove it

Japanese knotweed is one of the most difficult invasive plants to eradicate. Cutting or mowing alone stimulates the rhizome network to produce more shoots. The most effective approach combines repeated cutting with systemic herbicide application (glyphosate or imazapyr) during the growing season. Forestry mulching can clear the aboveground growth, but the rhizome system will require ongoing herbicide treatment over multiple growing seasons to exhaust the root reserves.

Purple Loosestrife

Purple loosestrife is an invasive wetland plant that has colonized marshes, ditches, and wet areas across Indiana.

How to identify it

Purple loosestrife grows 3 to 7 feet tall with square stems and opposite or whorled lance-shaped leaves. Its most distinctive feature is the dense spike of magenta-purple flowers that blooms from mid-summer through early fall. A single mature plant can produce 2 to 3 million seeds per year.

Where it grows

Wetlands, marshes, stream banks, drainage ditches, and any consistently moist area. In Northern Indiana, with its many lakes, rivers, and agricultural drainage ditches, purple loosestrife is a common sight in wet areas.

Why it is a problem

Purple loosestrife forms dense monocultures that displace native wetland plants like cattails, sedges, and native wildflowers. These native plants provide food and habitat for wildlife — when purple loosestrife takes over, the habitat quality drops dramatically. Its seed production is staggering, allowing rapid colonization of new areas.

How to remove it

Small infestations can be hand-pulled, making sure to remove as much root as possible. Herbicide application (glyphosate formulated for aquatic use) is effective on larger stands. Biological control using Galerucella beetles — released by state agencies — has been successful in some areas. Purple loosestrife grows in wet areas where forestry mulching equipment typically cannot operate, so removal usually relies on herbicide or biological control rather than mechanical clearing.

Garlic Mustard

Garlic mustard is an invasive biennial herb that has spread through woodlands across Indiana, displacing native wildflowers and disrupting forest floor ecology.

How to identify it

First-year garlic mustard forms a low rosette of kidney-shaped, scalloped leaves at ground level. In its second year, it sends up a flowering stalk 1 to 3 feet tall with small white four-petaled flowers. Crushed leaves smell distinctly like garlic. Seeds are produced in slender pods that split open in summer.

Where it grows

Woodland understory, forest edges, shaded roadsides, and along trails. It thrives in partial to full shade and is one of the first plants to green up in spring. In Northern Indiana, it is widespread in deciduous woodlands and shaded areas along streams.

Why it is a problem

Garlic mustard releases chemicals into the soil that disrupt the mycorrhizal fungi that native trees and wildflowers depend on for nutrient uptake. This gives garlic mustard a competitive advantage while weakening native species. It displaces spring ephemeral wildflowers like trillium, bloodroot, and wild ginger — species that define a healthy Indiana woodland floor.

How to remove it

Hand-pulling before seed set (April through early May) is the most effective method for small to moderate infestations. Pull the entire plant including the root. Garlic mustard does not resprout from roots like woody invasives, so thorough pulling can eliminate a population over 3 to 5 years of consistent effort. Herbicide application (glyphosate) works for larger areas but risks damaging native plants nearby. Forestry mulching is not typically used for garlic mustard since it is a ground-level herb rather than woody vegetation.

How Forestry Mulching Helps with Invasive Removal

For woody invasive species — bush honeysuckle, autumn olive, multiflora rose, Callery pear, and tree of heaven — forestry mulching is one of the most efficient removal methods available. Here is why:

• Scale. A forestry mulcher can clear acres of dense invasive growth in a single day. Hand-cutting the same area could take weeks.
• Thoroughness. The mulching head grinds stumps to grade level, which is more thorough than simply cutting at the base. The mulch layer suppresses regrowth by blocking sunlight from reaching the stump.
• Soil protection. The mulch left behind prevents erosion on the newly cleared ground and suppresses weed seed germination.
• Access restoration. Dense invasive thickets — especially honeysuckle and multiflora rose — make fence rows and woodlands impassable. Mulching restores access so that follow-up treatment, fencing, or management can take place.

For the best results, plan for one round of follow-up treatment 6 to 12 months after the initial mulching. Species like bush honeysuckle and autumn olive will resprout from surviving roots. Spot-treating the resprouts with herbicide during the growing season finishes the job that the mulcher started.

For more information on how forestry mulching works and what it can handle, see our complete guide to forestry mulching.