PIP Posey Invasive Partnership

04/07/2026

Invasive Plant of the Month - Garlic Mustard
by Angel Okray

Garlic Mustard (Alliaria petiolate), native to Europe and Asia, was introduced to the United States as an edible herd. Escaping cultivation, it now poses a threat to native flora as it quickly invades forest floors.
IDENTIFICATION: Garlic Mustard is a biennial herb, meaning it has a two-year life cycle. In its first year, it forms a low growing rosette: a cluster of dark green, broadleaf leaves with scalloped edges growing low to the ground. In its second year, it can grow nearly four feet tall with multiple stems of triangular, sharp toothed leaves and small white flowers at the top of each stem. Garlic Mustard develops a deep, slender taproot that often has a “S” shape. Both the leaves and the roots have a distinct garlic smell when crushed.
ECOLOGICAL THREAT: Garlic Mustard is a serious threat to forest beds, an essential part of the ecosystem where insects and native wildflowers typically thrive. Garlic Mustard blooms early in the spring and can quickly become a monoculture, outcompeting native species. Its root system also releases chemicals in the soil that disrupt the underground network of fungi and even inhibits the growth of trees. An average Garlic Mustard plant produces 360 seeds, but single plants have been known to produce as many as 8,000 seeds. The seeds do not carry well in the wind, but they can spread by attaching to birds, deer, and even your boots.
CONTROL: The most effective way to kill Garlic Mustard is to remove it before it sets it seed in its second year. The taproot does not anchor into the ground well, so the entire plant can easily be pulled out of the ground. It must be bagged and removed from the woods, or it will still disperse seeds. Do not compost. Repeating treatment each year is necessary because of its biennial growing cycle. Removing Garlic Mustard in its first year is more challenging because it is harder to see in its clusters close to the ground. In this stage, it can be carefully sprayed with a low percentage glyphosate to kill the root and preventing it from returning the following year. However, it will still be necessary to revisit the site the following year to remove any plants that were missed.
FUN FACT: Garlic Mustard is considered generally safe for human consumption, but it is only recommended to eat in moderation because of its hydrogen cyanide production. Younger plants can be eaten raw, but older plants should be cooked thoroughly. This spring, you can gather some leaves from young plants and try making garlic mustard pesto!

04/04/2026

PIP will be participating at this event. Please come out and see us!

The WillowTree Spring 2026 Newsletter is out! Checkout what we've been up to! https://mailchi.mp/fd69993638bf/willowtreepc_september2025-180303

03/17/2026

Invasive Plant of the Month: Callery Pear (Pyrus calleryana), also known as Bradford Pear. This article was contributed by Marlene Huffaker.

Callery pear spreads by seed and is native to Asia. Introduced to the U.S. in the early 1900s as the cultivar ‘Bradford’ for use in research, it was considered as a potential means to develop resistance to fire blight in edible pears and quickly became a landscaping favorite for its springtime flowers, autumn color and pleasing shape. ‘Bradford’ was believed to be sterile, but quickly cross-pollinated and produced viable fruit. One of the earliest bloomers of springtime, Callery pear is now found in a wide range of environments from native woodlands to vacant lots and other disturbed sites. It occurs in much of the eastern half of the United States. Common cultivars include ‘Cleveland Select,’ Autumn Blaze,’ Chanticleer’ and Whitehouse. All produce large crops of tiny, hard fruits, which appear in the fall and are almost woody until frost softens them, after which they are readily eaten by birds and other animals, thus dispersing the seeds. Dense thickets form and can outcompete native plants. The thickets are often thorny, making physical removal difficult.

Identify Callery Pear by its leaves, which are arranged alternately and are rounded in shape. The margin is finely serrated with a distinctly wavy texture. The top of the leaf is a dark, rich green. In early spring, white flowers are densely clustered with five petals. The blooms typically have a strong, unpleasant aroma, often likened to rotting fish. In winter, the trees are identifiable by their rounded crown.

Excellent Indiana native alternatives include Allegheny Serviceberry, (Amelanchier laevis), Fringe Tree (chionanthus virginicus) and Pagoda Dogwood (Cornus alternifolia), to name a few.

03/05/2026

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What is Allelopathy and Why Should you Know About it?

Allelopathy is a biological phenomenon in which plants release biochemicals (allelochemicals) into their environment that influence the germination, growth, survival, or reproduction of surrounding vegetation. These compounds can be exuded from roots or released as plant material decomposes, effectively altering the soil chemistry.

Several invasive species, including bush honeysuckle and garlic mustard, exhibit strong allelopathic properties. Because these species evolved outside our region, native plant communities have not developed resistance to their chemical compounds. This gives the invaders a competitive edge, allowing them to suppress natives, disrupt mycorrhizal fungal relationships, and reduce overall plant diversity.

Why it matters: Managing invasive plants isn’t just about removing visible vegetation. It’s about restoring ecological processes and soil conditions that native species depend on to survive and regenerate.

For more information on allelopathy check out this article from 2021: https://link.springer.com/article/10.1007/s10530-020-02383-6

For more information on invasive species check out our website: www.sicim.info

03/04/2026

Check it out! Please register by calling Warrick SWCD or using QR Code below.

03/01/2026

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02/24/2026

02/23/2026

This week is Invasive Species Awareness Week for the State of Indiana! See Governor Mike Braun's Proclamation.

PLEASE make your plans for 2026 to take action to control invasive species and consider participation in W**d Wrangles. Watch this page for opportunities in Posey County.

02/08/2026

PIP Invasive Plant of the Month: Amur Bush Honeysuckle, aka Bush Honeysuckle

Authors note: Plants are usually referred to as a common name, e.g. Bush Honeysuckle. Because nature is complex, the use of a Botanical Name, denoted by Genus and species, is more accurate and can describe related species and hybrids in a particular Genus.

One of the more aggressive and damaging invasive plants in Indiana are the four species of Asian Bush Honeysuckle shrubs, also known by its common name Amur Honeysuckle. (Note, these are different than Japanese Honeysuckle Lonicera japonica, which is an invasive vine.)

By far, the dominant Bush Honeysuckle in Posey County is Lonicera maackii.

The other three species, Lonicera tartarica, Lonicera morrowii, and the hybrid Lonicera x bella have been reported in central and northern Indiana.

These plants are similar, upright shrubs reaching heights of 6’ to 15’ tall, with opposite leaves and paired white flowers (tartarica flowers are pink), with clusters of semi-translucent red berries, where the soft woody tissue (pith) in the center of a woody stem naturally decomposes leaving a hollow stem.

Ecological Threat

These shade tolerant shrubs are among the first plants to leaf out early in the spring and drop their leaves late in the fall, growing near the edge of or in a woodland, and their dense foliage shades the forest floor, leaving bare soil resulting in the reduction of native plants that provide food and protection for insects, birds, and animals. Woodlands can rapidly be filled with these bush honeysuckles species since deer don’t eat them as they prefer to graze on native plants. This results in a severe decline in native plants, habitat, and pollinators, and can severely limit forest succession.

Control Methods

The best control methods are to hand pull the smaller plants by hand in the spring after a good rain shower. Try to get as much of the root structure out of the ground. For larger plants cut the woody stems close to the ground, before the fruit appears, with loppers or a chain saw (wear the proper personal protective equipment when using a chain saw) and then daub the stumps, within two minutes of cutting, with 20% glyphosate. An inexpensive dauber is the Racquet Art Dab-it applicator (available on AMAZON in various sizes). Don’t be surprised if you have to repeat the treatment the following year or two.

Read and follow all the label directions for use on all herbicides and, make sure what you purchase contains only glyphosate or glyphosate in the form of its isopropylamine salt as the active herbicide.

These products may contain a surfactant that acts to spread and stick the herbicide of the leaves and bark, increasing the effectiveness of the glyphosate. Do not get glyphosate on the any surface of a plant you do not want to harm.

Glyphosate was developed by Monsanto and sold under the brand name ‘Roundup’, but now herbicides are being marketed with the Brand name Roundup printed on the product container that may or may not contain glyphosate along with other more potent herbicides that can cause collateral damage.

For example, there is a product called Roundup Poison IVY which contains Triclopyr triethylamine salt, Fluazifop-P-butyl and Diquat dibromide, it doesn’t even contain glyphosate, but this product can migrate in soil and damage or kill a wide variety of vegetation indiscriminately, including trees. This material is labeled to kill ‘poison sumac’ which is a misnomer for Toxicodendron vernix, colloquially known as ‘thunderwood’, a native shrub that grows to 30ʹ and prefers the wet clay soils in swamps, is not a true sumac. Our native sumacs all in the Genus ‘Rhus’, and are important native shrubs for food for birds, habitat and insects, a perfect plant for poor soils.

And by the way, the berries produced by two Poison ivy species that are native to North America, Toxicodendron radicans and Toxicodendron rybergii, are an excellent source of nutrition for birds.

Bottom Line, when using any herbicide, read the label, understand how to apply it and what herbicides are in it, and if unsure of anything consult the Web or someone in the know.

Identifying invasive species can be tricky. Consider getting a plant identification app for your phone; the ‘SEEK’ app is free, but a better app is ‘Picture THIS’, available with a 1-week, 1-month, or 1-year subscription.

References Invasive Plant Species Assessment Working Group (WWW.invasivespecies.IN.gov)