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Located at Utah State University in northern Utah, the Invasive Plant Science Lab is directed by Steve Young, researcher, instructor, and part-time triathlete.



The Invasive Plant Science Lab is located on the campus of Utah State University in the Department of Plants, Soils & Climate. Its purpose is to add to current knowledge as well as aid in the development of new approaches that reduce invasive plant populations and their negative effects on widely differing ecosystems.

Emphasis is placed on collaborative relationships with expertise in agriculture, natural resources, engineering, biology, economics, social science, and many other fields of study. Efforts are made to advance research through basic and applied studies and address educational needs through trainings and courses, and supporting Extension programs. 

Please take a moment to peruse the website to learn more about the Invasive Plant Science Lab.

Steve Young_1.jpg


(435) 797-0139 steve.young (at)

Dept. of Plants, Soils & Climate

4820 Old Main
Logan, UT 84322

Office: AGRS 323 (Upstairs from Luke’s Cafe)



Invasive plants present formidable management challenges. Yet, effective control depends on more than just application techniques. Equally important is knowing why an invasive plant is successful and how. Pick any invasive plant – spotted knapweed, tamarisk, cheat grass – and you’ll find research has been conducted on the ecology and biology. But, what is missing is the synthesis part. How do we take what is published in the literature and use it to create the most complete picture? The answer lies in the use of frameworks; from the simplest to the very complex.


When an effective framework is developed for invasive plants, our understanding is not only broadened, but we also start to see knowledge gaps. At the same time, we are able to identify weaknesses of invasive plants or at least devise research programs to find these, which are fundamental for effective management. An effective framework allows us to ask questions, like, “is ‘x’ invasive plant susceptible to abiotic conditions and the occurrence of extreme weather events? or “how does community composition affect competition by ‘x’ invasive plant?” or “do the genetics of a population suggest certain pre-dispositions of ‘x’ invasive plant?”

As researchers and managers, we most often want to know which invasive plant will show up next, when, and what will be the impacts. This way, we can plan for it or so we might think. However, once it shows up, it is often too late. If we knew more about ‘x’ invasive plant before it got to our farm, field, forest, or rangeland, then perhaps making predictions about it wouldn’t be so important. We can classify an invasive plant’s ability to succeed in increasing populations, establishing local dominance, or rapidly expanding their range using three broad factors of climate dynamics (weather), invader fitness (genetics), and ecosystem resistance (habitat).


By using a three-factor (weather, genetics, habitat) invasion framework, we can organize published empirical research in a way that shows what is known (or not known) about the success of any individual invasive plant. Then, conceptual models of each factor reveal its effect on each component of the invasion process (increasing populations, establishing local dominance, or rapid range expansion), which, again, is based on what has been published in the literature. With continued published studies, information is added on one or more factor, further unlocking the mystery of how an invasive plant is successful and identifying limitations.

The Invasive Plant Science Lab is using this framework, described in more detail by Young et al. (2017), as a basis for guiding research studies. Ultimately, the new information generated and combined with existing knowledge will lead to the developing more effective and sustainable management strategies.


Pick a plant

An invasive plant can be classified as a weed, a native, or an exotic. Most often it has progressed through the first two stages of the invasion pathway: transport and introduction. Once established, an invasive plant can remain non-invasive or invasive by increasing populations, establishing local dominance and rapid range expansion (see Framework). The factors contributing to a plant becoming invasive are discussed in more detail in the sections: Variable Landscapes, Climatic Regimes, and Test of Fitness.

In reality, any plant can become invasive if the conditions are favorable. Even native plants, such as eastern redcedar, have been known to aggressively populate and expand their range in places like the Central Prairies of the United States. While often thought of in negative terms, a weed has been defined more generally as “a wild plant growing where it is not wanted and in competition with cultivated plants” or simply, “a plant out of place.” The famous poet, Ralph Waldo Emerson defined a weed as “a plant whose virtues have not yet been discovered.”

The seemingly conflicting or at least vague definitions for invasive plants and weeds puts them in the eyes of the beholder. Thus, we each have our own “significance scale” with which we judge all plants in terms of their aesthetic value, contribution to the environment, and direct effects on neighboring species. Is your scale biased more towards aesthetics than environmental contribution? Are you aware of the effects that certain plants have on neighboring species? Is a contribution to the environment always positive or can it be negative when we think about ecosystem services?

The Invasive Plant Science Lab is addressing these kinds of questions for a wide range of plant species, but primarily those with known invasive and/or weedy properties. If you picked any plant, which one would it be and what would you want to know about it with regard to its value aesthetically, contribution to the environment, and effect on neighboring species?


Variable Landscapes

Landscapes vary widely across space and time (spatiotemporal). Among the many changing features are plants, including types, forms, and functions. Competition for resources depends both on the characteristics of the invader and the attributes of the native community and are not always mutually exclusive. For the invader, leaf size, root distribution, and plant height are important for obtaining water, nutrients, and light (Test of Fitness).

Macro- and microfauna, plant species composition, available nutrients, and soil type form the basis for the main biological and physical context of resident plant communities. Each of these either passively or actively shapes the plant community in concert with weather (Climate Regimes) and genetics (Test of Fitness). In sagebrush communities where once a keystone native species is reduced or removed [sagebrush (Artemisia spp.) itself], biotic resistance to invasion is reduced both through lack of competition and alteration of soil structure due to the change in community composition.

Animals and insects above- and belowground contribute to the dynamics of plant communities. The life histories of plant species contribute to the functional diversity of plant communities. Some have shown that the entire food web is a better predictor of biotic resistance than interactions among a select group of competitors. Likewise, the soil context is a key component of ecosystem resistance. Macro and micro-nutrients are spatially distributed throughout soils with uptake dependent on season, microbial community, and chemical bonding to minerals.

The landscape can affect an invasive plant, whether it is natural, semi-natural, or urban, almost as much as an invasive plant can affect a landscape, but in what ways, under what conditions, and for how long? These are the types of questions being addressed by the Invasive Plant Science Lab.


climate regimes

Climate plays a significant role in plant community dynamics, whether they are normal conditions (30-year averages), extreme highs/lows in precipitation and temperature, duration of extreme conditions, and rising atmospheric CO2 concentrations. Extremes in weather affect plants. Over the past decade, the increasingly large fluctuation from long-term average conditions has resulted in extreme high and low temperature and precipitation levels. During a normal year, drought or flooding may still negatively impact plants because of altered frequency and duration of precipitation. Increasing CO2 concentrations in the atmosphere are having a positive effect on the growth of certain plants (e.g., C3 plants), which could provide non-native plants with an advantage in the invasion process.

Case in point – In 2012, much of the US Midwest was gripped in one of the most severe droughts on record. While conducting experimental fieldwork at a site in Nebraska during June of that year, a single musk thistle (Carduus nutans) appeared to be in the bolt or early flowering stage, which is typical for the species at that time. Here, however, two things were unusual: this plant was less than 1 meter tall (with adequate moisture and light, musk thistle typically grows to heights of 1–2.5 meters before flowering), and was only 3 months old (the bolt stage, when it would produce a flowering stem and set seed typically occurs during the thistle’s second year). Interestingly, this plant died less than 3 weeks later, without producing flowers or seeds. Apparently, this particular plant was unable to successfully spearhead an invasion in this field because it could not complete its normal life cycle during a period of drought.

In temperate climates, episodes of heavy rainfall, summer flooding, and severe droughts are already occurring along with what some are suggesting will be a concomitant increase in the impacts from invasive plants, partly due to their more widespread distribution. Certainly, the effects of increased extreme weather patterns on facilitating or limiting plant invasions have not been studied extensively and will be a focus of the Invasive Plant Science Lab.


test of fitness

The strategies of many invasive plants to successfully establish in new habitats include rapid growth, small or large seed size, and prolific seed production, which are based on genetics. Specifically, plasticity, genetic mutation, phenological adaptation, and genetic selection contribute to plant reproduction and survival. Known as plant fitness, genetically superior plants that have mutated successfully are able to resist deleterious action(s) or condition(s) through growth, development, and phenology. The phenotypic traits displayed are an expression of those genes in a surviving plant. The traits are modifications that may or may not adapt to continued selection pressure(s).

Over a period of time, plant interactions with the environment may result in populations or individuals with higher fitness. The differences among species and even within species can be striking and seemingly consistent with the evolution of increased competitive ability (EICA) hypothesis. Some have suggested that the native habitat actually constrains some invasive plants, while the new habitat acts as a selection pressure for others.

Plasticity is an important trait for invasive plants as it allows one or a few introduced genotypes to acclimate in new and competitive habitats. In addition, invasive plant plasticity may evolve in response to new selection pressures (e.g., extreme drought events, Climate Regimes) during introductions into a range of habitat types.

What remains unknown is the intensity and duration of selection pressures needed to drive local ecotype creation and life history alterations among invasive plant species. Further, very little is known about the components of the invasion process and what may limit the success of yet to be introduced plants that are “born into” or “made” by their new habitat.


Monitoring & management

Much can be learned by monitoring invasive plants through research studies, which then contributes to determining the most appropriate level and type(s) of management. Should eradication be the goal or perhaps reducing the population and preventing satellite communities from starting? When should containment be used? In addition to removal of invasive plants using various chemical and mechanical tactics, other strategies can be used that suppress (e.g., cover crops) or compete with (e.g., revegetation) invasive plants. Often it is a combination of approaches (i.e., integrated weed management) that are the most successful.

The first priority should be to know enough about the biology and ecology of an invasive plant and any weaknesses, real or perceived, be they related to growth, development, and/or reproduction (A Framework). It is imperative that we know the underlying mechanisms of how and why invasive plants exist, where they exist, and the conditions in which they exist because this will help in designing the most effective and sustainable strategies for managing invasive plants.

In addition to developing effective strategies, successful implementation is reliant on adoption. However, proof is the basis for most to adopt a new practice, method, or strategy or change an approach even slightly. What kinds of questions are being asked by those who are dealing directly or indirectly with invasive plants? Do they want to lower their input costs? Do they want to diversify their tactics? What are they seeing on the lands that they manage or own that is of concern or a benefit? What is the role of the Invasive Plant Science Lab in helping to answer or at least address these and other similar questions?

See the kinds of research being conducted and training being offered by the Invasive Plant Science Lab for practitioners, graduate and undergraduate students, researchers, and citizen scientists.


Join In……


Are you a grower or land manager? Do you deal with invasive plants in an agricultural or rangeland context? Do you work in Extension assisting clientele? Are you involved in policy or legislative activities that address land use? The Invasive Plant Science Lab is in the process of developing a 3 to 5 day short course on invasive plant ecology and management as part of Utah State University’s certification program. Please contact the Lab for more information.

Graduate Students

Are you considering graduate school or in the application process? Have you decided on an area of study? Invasive plants are just about everywhere and span a variety of research topics, both applied and basic, such as restoration, ecology, biology, modeling, and technology. The Invasive Plant Science Lab has projects underway investigating the long-term dynamics of invasive plants, extreme drought as a selection pressure on invasive plants, the use of cover crops to suppress invasive plants in organic and non-organic agricultural systems, the ability of established plant communities to resist invasion, and robots for weed control. If any of these are of interest, you have your own idea or just want to know more, please contact the Lab.

Graduate Research Assistantship position currently available. See the announcement

Undergrad Students

·Are you looking for part-time work that will contribute to important research? Do you like to do a variety of tasks and keep a flexible schedule? Maybe you’re the type that likes project work that has a definite start and finish. The Invasive Plant Science Lab has openings for highly motivated and enthusiastic individuals with a strong desire to learn and advance their careers. Not interested in jumping right in? Then try the course, Fundamentals of Integrated Weed Management (PSC 5550/6550), which is offered during fall semesters. Please contact the Lab for opportunities.

New! Beginning in Fall 2019 Semester, the Invasive Plant Science Lab and the Utah State University Honors Program are partnering to offer an Integrated Honors Research Experience for Undergraduates. The year-long, hands-on research program is a combination of coursework and lab work capped by a two-week study abroad in Taiwan at National Chung Hsing University. Qualifying students will receive honors points and USU credits. All majors welcome. Apply today!

Lab members

Steve Young,    Director    Read my bio  here   Publications on  Google Scholar

Steve Young, Director

Read my bio here

Publications on Google Scholar

Hailey Buell, MS Student   Project: Control of annual invasive grasses using multiple approaches

Hailey Buell, MS Student

Project: Control of annual invasive grasses using multiple approaches

Chris Jones, Undergraduate Student (Statistics)   Project: Modeling patch spread dynamics of invasive plants in natural areas

Chris Jones, Undergraduate Student (Statistics)

Project: Modeling patch spread dynamics of invasive plants in natural areas

Rose Sepesy, PhD Student   Project: Response to extreme drought by a model invasive plant,  Phragmites australis

Rose Sepesy, PhD Student

Project: Response to extreme drought by a model invasive plant, Phragmites australis

Dani Thiemann, PhD Student   Project: Crop and invasive plant competition in agronomic production systems of arid climates

Dani Thiemann, PhD Student

Project: Crop and invasive plant competition in agronomic production systems of arid climates

Lab news!


Steve starts new position at USU and creates the Invasive Plant Science Lab (IPSL)

Project on integrated tactics, including cover crops, for controlling kochia funded by WIPMC

Rose Sepesy joins IPSL with an interest in riparian systems. She is from Ohio.

Chris Jones joins IPSL as the first undergraduate and statistics major!

Hailey Buell joins IPSL. She is from Arizona

IPSL continues to add new members – Dani Thiemann will start on her PhD. Another Ohio native

IPSL first annual road trip to southern UT. Some cool research and ‘easy’ hiking to see the Great Arch.

Steve presents at ESA on Phragmites and water politics.

Utah Public Radio reports on IPSL research on cover crops and weeds

Steve talks robots and weeds at the ASA meetings in Baltimore

Rose and Hailey rock the crowd with their seminars at the PSC Seminar Series.


1/1 Happy New Year!
IPSL is one year old

Dani, Rose, Chris, and Hailey presented posters and Steve gave an invited talk at the Western Society of Weed Science meetings in Denver, as the city shut-down due to a freak blizzard.

Field season is still on hold due to the excessive wet spring.

Paper published by the IPSL in Science of the Total Environment

A manhole for studying plant roots? Should be part of every plant ecology lab’s inventory. Should be ready by fall…..

Steve heads to Taiwan to spend two weeks meeting with faculty at National Chung Hsing University to establish new collaborations.

Crops are finally planted at Kaysville and Cache Junction!

IPSL develops new research and study abroad program with USU Honors and the Office of Global Engagement.

Sagebrush, ant mounds, and cheatgrass - the focus of a new study near one of Utah’s most active bomb testing sites.

IPSL hosts Dr. Haifeng Xing, visiting scientist from Inner Mongolia Agricultural University, to work on allelopathy in wheat for controlling weeds.

Undergraduate student, Andrew Jouffray in Computer Science, will join the IPSL to help build robots that can seek and destroy weeds.

Carol Rowe joins the IPSL to work on a new project identifying invasive plant hotspots in Utah.

Competition studies in the greenhouse support our findings in the field. Additional research being planned.

New project initiated to look at the interaction of Puccinia punctiformis, a biocontrol agent, and Canada thistle.