Aiding and Abetting Invasive Species


It’s bad enough that invasive species are taking over our prairies and other natural areas.  Why do we insist on helping them do it?

When my dad was in high school in the 1960’s, he planted trees and shrubs behind the pond in my grandpa’s pasture as part of a 4H conservation project.  The species he planted – Russian olive, eastern red cedar, honeysuckle, and multiflora rose – were all promoted as conservation trees at the time but considered to be invasive species today.  The honeysuckle and multiflora rose didn’t make it, but we’ve still got a strong population of Russian olive and cedar trees today, and now that I’m taking over the management of the pasture, I’m making plans to eradicate them.  I give my dad a break on this one because it was a long time ago.  Unfortunately, less has changed in the last 50 years than you might hope for.  (See my earlier post on invasive trees in prairies)

Eastern red cedar trees are native to Nebraska, and so should probably be labeled as “aggressive” rather than “invasive” – though they can certainly take over grasslands, they’re only a problem where fire has been removed from the ecosystem.  Russian olives, on the other hand, are clearly invasive species.  Many thousands of dollars are being spent trying to remove them from riparian areas around Nebraska and many other states.  Why, then, are we still planting Russian olives??  They are still listed and sold as conservation trees in Nebraska, and several agencies have long been providing cost-share dollars and promoting both the planting AND eradication of Russian olive trees (a situation that is just starting to change).

A Russian olive tree resprouting after a late-spring prescribed fire. Russian olives and most other deciduous trees are particularly difficult because of their capacity to re-sprout.

Siberian elm is another species that is being both promoted and controlled.  The species was first introduced to the United States in 1860.  When Dutch elm disease started wiping out American elms in the 1930’s, Siberian elm gained popularity because it was much less susceptible.  It was also promoted as a substitute for privet (another introduced invasive species) in hedge plantings.  Today, Siberian elm is widely recognized across the country as an invasive species (it is an official noxious weed in New Mexico) and is one of the most aggressive trees invading prairies in Nebraska and other states.  Its abundant wind-dispersed seeds allows it to quickly overwhelm grasslands (and grassland managers) with numerous small saplings.  They are common urban trees – but largely reviled because of their brittle branches and unattractive crown shape.   Notwithstanding its record, however, this ugly aggressive non-native tree is still being promoted as a conservation tree in Nebraska and elsewhere, and the U.S. Department of Agriculture’s Plant Materials Center in Kansas is actually developing an “improved” cultivar for use in the western Great Plains (see page 82 of this report for details).

Unfortunately, Russian Olive and Siberian elm are only two of many examples of introduced species that are simultaneously viewed as useful and invasive by different constituencies.  Nebraska’s newest official noxious weed is Japanese Knotweed, which has numerous hybrids (most of which are invasive) that can still be purchased through garden catalogs.  Sericea lespedeza, a horrible invasive plant in the southern prairies (and a noxious weed in Kansas and Colorado) is still promoted as a forage and wildlife plant by Auburn University.  In fact, sericea’s status as a “crop” is preventing the development of biocontrol agents that may be the only hope of controlling its spread.

Invasive grasses such as smooth brome, tall fescue, and reed canarygrass are being promoted as forage crops for livestock at the same time that huge amounts of money and effort are being spent to keep them from overrunning prairies.  Perhaps most frightening, Monsanto and Scotts have developed strains of Kentucky bluegrass and creeping bentgrass (both invasive grasses in prairies) that are resistant to glyphosate herbicide (aka Roundup) for use in turfgrass applications.  The possibility (probability) that those Roundup Ready species will either escape from planted areas or hybridize with naturalized populations is apparently being ignored – in spite of the fact that the bentgrass has already escaped from test plots in Oregon.  There are plenty of other examples of introduced ornamental or agricultural plants that we’re assisting with their invasion of natural areas, but the list is too long and depressing to present here.

Why do we have such trouble agreeing whether species are helpful or harmful?  A big part of the problem is the diversity of organizations and entities that work to introduce, promote, evaluate, and/or control plant species.  There is no single clear controlling entity that can designate species as being invasive or not.  Because of that, an internet search is not usually an effective way for a member of the general public to find out whether or not a species is invasive.  While there are excellent sites like the USDA’s PLANTS database that list whether the species is considered to be invasive or a noxious weed in any states, a general search for species like sericea lespedeza brings up some websites that promote it as a wonder plant and others that denounce it as a nasty weed.  What’s a person to believe?  (In this case, it’s a nasty weed…)

To further confuse things, those who continue to promote the use of invasive species often claim that the species aren’t invasive in the habitat type or geographic area they’re promoting them for.  I often hear that Russian olive trees are safe to plant as long as you only put them in uplands, and not in lowlands where they become invasive.  This argument appears to rely on the assumption that the wildlife species eating the Russian olive’s “wildlife friendly” fruits don’t move between upland and lowland habitats.  Considering a species safe in one state when it’s demonstrated to be invasive in a nearby state is equally illogical.  True, it can be difficult to predict whether a species will be able to thrive in one area or another without actually testing it, but given the cost of controlling invasive species, why take a chance?

Siberian elms and smooth brome - a pretty nasty one-two punch of invasive species.

How Do we Fix the Problems?

One part of the solution to these issues is to make the general public more aware of which species are considered to be invasive in their area.  Nebraska is currently building a set of lists that will identify known and candidate invasive species, and will rank them by severity and the appropriate response needed (e.g. – prevent their introduction, eradicate current populations, or contain the spread of current populations).  It’s surprising that lists such as this are not more widely available across the country, but they’re actually difficult to find.  Of course, while lists of invasives are helpful, they only work when they’re used.  It’s difficult to imagine many homeowners taking the time to cross check their annual garden catalog wish list against an invasive species list before ordering.  Most consumers assume that if they can buy it, it must be safe – something that is far from true – and the conflicting information found on the internet and in other sources only serves to further confuse and frustrate people.

Educating the general public about the value of using native species for both urban and rural plantings – thus avoiding the risk of introducing species that may become invasive- is another important approach.   I’m a big fan of using native plants, but I’m also realistic about both the difficulty of marketing natives and some of the complications associated with “native” plants.  One of those complications is that it’s very difficult for the public to know which plants are actually native.  For example, mixtures of wildflower or wildlife habitat seeds that are commonly sold in Nebraska and other prairie states include both native wildflower species (though often with genetic origins from far away states) and non-native species, some of which are invasive.  Invasive species that are often included in wildflower mixes include oxe-eye (shasta) daisy, damesrocket, baby’s breath, bouncing-bet, birdsfoot trefoil, red clover, chicory, common St. Johnswort, Queen Anne’s-lace, sweet clover and many others.   It’s not reasonable to expect consumers to be able to determine which species are safe and which aren’t.  (What could be dangerous about wildflowers?)

The demand side of the equation (consumers) is an important place for us to focus attention, but the only way we’re really going to solve the problem is by also working on the supply side.  Somehow, we have to build consensus and understanding between those who are fighting invasive species (e.g. conservation and agriculture groups and landowners) and those who are introducing and promoting new plants (e.g. some agencies, universities, and nurseries).  It’s certainly not going to be a quick or easy process, and it’s not going to solve the problem completely – but the only other option is to continue fighting an ever-growing list of invasive species.

Rather than sniping at each other across fences, we need to build partnerships that bring together nursery organizations and noxious weed control agencies, tree advocates and prairie biologists, and forage specialists and native plant enthusiasts.  The initial partnerships don’t have to be (can’t be?) built around the sources of greatest disagreement.  For example, nursery owners and noxious weed agents might come together because they both see the need for improved influence over nurseries that purposefully (or neglectfully) sell plants that are clearly illegal to sell – nursery owners might be concerned about reputational risk of the nursery industry as a whole, and noxious weed agents would want to prevent introductions of dangerous plants.  More difficult discussions about how to handle the sale of plants that are potentially, but not definitively, invasive can wait.  Once a rapport has been established, it’s much easier for both sides to see and appreciate the point of view of the other – and both have a stake in maintaining the relationship by finding ways to compromise.  In some cases, it might not be possible to build partnerships right away, but important first steps toward building relationships can include things as simple as inviting each other to attend meetings, join field trips, or give presentations on current and future projects.  Anything that gets people into the same space so they can see each other as people rather than adversaries is likely to be productive.

Invasive species are one of the biggest threats to prairies (maybe the biggest) and the issue is much bigger than simply attacking species as they appear.  If we can work to prevent the next leafy spurge or sericea lespedeza from being introduced or released in the first place, just about any level of effort would be worthwhile.  It’s up to all of us to raise awareness about the risks of introduced species and the benefits of native species.  Even more importantly, it’s up to us to work with those who see things differently than we do to establish relationships and common understanding.  While it’s tempting to go around with a rolled-up newspaper and whack those who appear to be acting irresponsibly, that’s not likely to be very productive.  Maybe we should start by sending them (carefully vetted) flowers instead!

17 thoughts on “Aiding and Abetting Invasive Species

  1. Chris,
    Thank you for writing about this issue. I am always perplexed how a tree or shrub is sold through a County, City or watershed district sale and at the same time is listed as an invasive species by the State DNR.

    • Hi Wanda,

      Good question. I’m not familiar with E. commutata (silverberry) because we don’t see it in Nebraska. It looks like one obvious difference is fruit color (red for silverberry and yellow for Russian olive). It also looks like Russian olive tends to grow from a single trunk while silverberry tends to have multiple stems, but I’m just looking at things on the internet – not a good key. Apart from that I’m not very qualified to answer. We’ll see if we get some help from other readers…
      – Chris

  2. Chris,
    I too have wondered about this problem for a long time. Different conservation groups with vastly different priorities work at two different ends of the spectrum. One plants the invasive weeds under the guise of improving habitat while the other tries to kill what the other planted. I too like the idea of offering an olive (hopefully not Russian) branch of peace and working through partnerships to achieve this goal.

    Your post inspired me to discuss this issue with the local greenhouses in town and I will be taking that up in the coming weeks. Hopefully it will produce fruit and improve local understandings of invasive species and their impacts on habitat. Because I already have a relationship with the local NRD I’m also going to try to talk with them about the trees they offer in their plantings. Hopefully that too can turn the tide of planting invasives and propagating our own job security.

    Thanks again Chris for another insightful and poignant blog post!

  3. Lots of obstacles to overcome here (you can’t even tell some “Home of Arbor Day” residents that cutting down invasive cedar trees in prairies is good,) but the cause is worthy.
    Go get ’em.

  4. Look on the bright side – it could be kudzu.

    This is pretty frightening, the lack of consensus. But I’m surprised at invasive species being able to develop a stronghold among native plants, especially in what seems to be a resource-restricted ecology like a prairie. Is it a lack of “predators” at play, or better genes, or more rapid dissemination capabilities of the invaders?

    Speaking of Arbor Day, has anyone wandered around the Lodge’s grounds and seen invasive species? You know, like apples?

    • Each invader has its own individual strategy. Some have a chemical warfare strategy where they can alter the chemical makeup of the soil to favor themselves over others. Some grow earlier than most prairie plants and capture moisture and soil nutrients before other species emerge. Some withstand fire or grazing better than others. Lack of herbivores/pests certainly plays a role too – if you’re an invader from Europe and produce 1000 seeds, none of which get eaten because you’ve escaped from the insects/fungi/etc that attacked your seeds in your native country, you’ll get an advantage over a native plant that produces 1000 seeds but only has 10% survive insects/fungi/etc.

  5. Chris,

    I’ve been lurking in the shadows for a while reading and not commenting on the blog. Great work, and I also enjoyed your book. A Nebraskan friend I met at SFASU in Nacogdoches, TX introduced me to your work.

    There is currently some interesting legislation going through the Texas Legislature on this issue.


    Please, keep the thought provoking blogs coming.

    • Thanks Tim – I’m glad you enjoyed the book. And thanks for the link – it’s timely since we’re trying to define invasive species here, and have no legal authority for the list to mean anything (nor are we trying to claim any).
      – Chris

  6. Chris;
    Whata great example of the complex ecosytem of the Prairie and nature in general.
    The best solutions will come from -just what are doing – rasing awarenes and getting people thinking and working on these issues.
    Well done- Thanks

  7. Chris,

    My name is Jed Wagner and I serve as Programs Director for the Nebraska Association of Resources Districts (NARD). One element of my responsibility is to manage the NARD’s tree program. The NARD works closely with all of Nebraska’s 23 natural resources districts (NRDs) in helping to manage Nebraska’s conservation trees and shrubs. I offer below several facts in response to your March 1 post titled Aiding and Abetting Invasive Species.

    1. Two of the links that you referenced in your post regarding Russian olive and Siberian elm trees were outdated links to the NRDs’ publication titled Conservation Trees for Nebraska. This popular booklet was updated and reprinted in 2010 by Nebraska’s NRDs in partnership with the Nebraska Forest Service (NFS.) Updated information can be found at

    2. For your readers’ information, NRDs work closely with the NFS and the Nebraska Natural Resources Conservation Service (NRCS.) NRDs consult NRCS’ Conservation Tree and Shrub Groups (CTSG) recommendations when making decisions as to which conservation tree and shrub species to independently offer for sale to Nebraska landowners. Furthermore, any species offered by a NRD that is not listed in NRCS’ CTSG is ineligible for cost-share assistance from both the NRD and from the NRCS.

    3. In our latest publication, Russian olive has been removed as it is no longer approved in NRCS’ most recent CTSG listing (November 2009; Siberian elm remains in our updated booklet but is recommended only for Vegetative Zone I located in Nebraska’s panhandle. The NRDs’ updated booklet states that “Siberian elm should be planted only on severe sites where other species are likely to fail. Siberian elm can be invasive on pasture lands in the central and east because of its prolific seeding.” NRCS also lists Siberian elm in their CTSGs as a species recommended only for Vegetative Zone I in Nebraska.

    4. Land management recommendations in Nebraska have evolved over time. Practices approved and recommended in the past by various conservation organizations may not be recommended today by these same organizations. Many resource conservation objectives are multi-faceted; it can be difficult for land managers to meet all objectives simultaneously, though we all try our best to do so. Geography plays a large role in many categories of best practice. New science and hindsight are both catalysts for change.

    5. I do not disagree with your assertion that Nebraska’s multiple land management organizations, both public and private, are not in complete consensus regarding some conservation tree objectives and best practice. This fact does not infer that these organizations to not appreciate each others’ points of view. The NARD will be happy to meet with any organization, or group of organizations at any time to discuss conservation tree planting best practices designed to minimize negative effects while at the same time protecting lives, protecting property, and protecting our future.

    • Jed – I appreciate your polite and comprehensive clarification. I apologize for using outdated weblinks – they were what popped up when I went looking for information on what was being planted and/or recommended.

      As you say, there is no consensus among conservation entities about species to plant or about which species may be invasive (or about a number of other things!). Consensus isn’t necessary, as long as there is good communication, although it does create unfortunate confusion among the public. I’m not sure there’s a solution to that – organizations are certainly entitled to create their own priorities – and don’t have to conform to what others think (that’s how innovation happens).

      I knew that NRCS had de-listed Russian Olive within the last year or so, which is great news to me. I hope Siberian elm will follow at some point, but I do appreciate the commentary that accompanies the listing of it in NRD publications.

      And finally, thanks for your offer to meet. I think it’d be great to have you or someone else attend a meeting of the Nebraska Invasive Species Council sometime to have a discussion on this topic. Constance Miller (NRCS) and Scott Josiah (NFS) both sit on the council and represent many of the same views you share, I think, but it’d be interesting and productive to have a conversation about tree planting programs sometime. I’ll communicate separately with you about that.

      Thanks again.

  8. HI Chris.
    I enjoyed reading “The Prairie Ecologist” Thanks for the photos too. And the molting grasshopper. Whoever messed up people’s minds into replacing the native prairies with exotic species was terribly wrong. Let’s hope more will come to appreciate hidden potentials of diverse native grass stands.

  9. In order to help the public find invasive species information, we (a few partners in Texas) created A “one-ring to rule them all” sort of website about invasive plants in Texas. We are expanding into pest and animals, but that will take time and contributions from other organizations.

    Between the website and other publications put out by TX Parks & Wildlife, TX Forest Service and other organizations, the public seems to be getting the information. And the bill mentioned by Tim is probably in direct response to our efforts.

  10. Recheck your sources before spewing the hate: several varieties of Reed Canary are derived wholly or partially from native North American stock. Palaton in particular is an excellent candidate for replacing the bane that is tall fescue (which despite it’s ecological harm, provides the means of survival for many a Midwest smallholder cattle operation year in and year out).
    You’re barking up the wrong tree with your partnership designs. The true destroyer of prairie is the greed that partitioned it. If it isn’t free as a whole, it can’t be healthy. Stewardship will always take a backseat to profits in our current economic paradigm.


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