Blowing Against the Wind?

As I mentioned last week, I recently spent a couple days helping our land manager, Nelson Winkel, pull garlic mustard at our Rulo Bluffs Preserve in southeast Nebraska.  The invasive species has just started to invade our property within the last several years.  We’ve heard stories from colleagues in other places about beautiful woodland plant communities turning into monocultures of garlic mustard within a relatively short time period.  We’d sure like to keep that from happening at our Preserve.

So, we pulled garlic mustard plants.  A lot of them.  On the first day, I figured we pulled at least 25,000 plants.  That’s a very conservative estimate.  The second day was longer, but we did more searching and less pulling.  This wasn’t the first trip to pull either, so we were just trying to get what was leftover from the previous efforts.

Nelson Winkel, showing off one patch's worth of pulled garlic mustard plants.  The Nature Conservancy's Rulo Bluffs Preserve - Nebraska.

Nelson Winkel, showing off one patch’s worth of pulled garlic mustard plants. The Nature Conservancy’s Rulo Bluffs Preserve – Nebraska.

The Rulo Bluffs Preserve is 444 acres.  Hand-pulling weeds doesn’t seem like a very sustainable strategy for invasive species control at that scale.  In fact, it’s downright depressing because we pull more plants from more locations every year.  We’re clearly not winning.  So why bother?

It’s a good question, with several answers.  The first answer is that we’ve got some ideas for increasing our effectiveness.  Nelson and I talked as we worked about how we might put together a small army of volunteers to come help us pull each spring.  The big challenges are that the site is far from population centers (more than two hours from Lincoln and Omaha), has difficult terrain to hike in, and garlic mustard doesn’t bloom at exactly the same time each year, so we’d have to schedule work days on fairly short notice.  On the other hand, I think there are people who’d be glad to help, and it is a beautiful place to work in the spring time – lots of warblers and other birds above, and plenty of woodland wildflowers below.

In addition to finding more people to help hand pull, we hope to decrease the number of plants we need to pull in the bigger, more established, patches by doing some herbicide work in the late winter.  Garlic mustard is a winter annual or biennial which germinates in one season, overwinters as a rosette (a few leaves, low to the ground), and then flowers in the late spring of the next year.  Our colleagues in more eastern states have been dealing with garlic mustard longer than we have, and have had luck spraying the rosettes with Glyphosate herbicide on warm February days.  Spraying in the winter works well because there are very few other woodland plants that are green (and thus susceptible to Glyphosate) in February.  They don’t usually spray in the early winter because many rosettes die on their own over the winter, and by waiting until February, they can focus only on those most likely to bloom in the coming year.  Nelson was marking the bigger patches we found with a GPS unit so he can find them next winter and try the spraying technique.

Small patches of garlic mustard such as this one might eventually be eliminated by hand-pulling.

Small patches of garlic mustard such as this one might eventually be eliminated by hand-pulling – especially if we find and treat them every year.  Larger patches are much more problematic.

The second reason we’re still trying to suppress garlic mustard is that I hope we can buy some time until better control options become available.  There has been some work to develop a biocontrol technique (using insects from the native range of garlic mustard), for example, and if something like that turns out to be effective, I want to be sure we still have some woodland left to save.  Unfortunately, I’m hearing that biocontrol development has stalled at the moment.  Apparently, in at least some places, people are seeing garlic mustard populations decline steeply on their own – as if the plants are outcompeting themselves and self-thinning.  That could be great news, but only if the native plant community rebounds as the garlic mustard declines, and I haven’t been able to find anyone who can tell me whether or not that’s the case.  I sure hope it is, but I’d feel better if the biocontrol folks kept forging ahead on the development of that control option anyway.  Regardless, I’m holding out hope that either garlic mustard will turn out to be a temporary nuisance (seems unlikely?) or that biocontrol or better control options will be developed in the next several years.  I could be naive, but at least it gives us something positive to think about while we’re pulling up thousands of garlic mustard plants…

While we look for better control options, we’re also trying to change the playing field for plant competition at Rulo Bluffs and give garlic mustard less of an advantage.  With considerable help from Kent Pfeiffer of Northern Prairies Land Trust, and funding from the Nebraska Game and Parks Commission and others, we’ve been trying to ramp up our stewardship work during the last several years.  We’ve not done as much burning as we’d like to, but are earnestly trying to change that.  Last fall, a contractor did some “hack-and-squirt” herbicide treatment to kill many of the smaller understory trees that are shading out the herbaceous plants on the ground.  We’ve also been doing mechanical shredding of brush on ridgetops to help the grassland, savanna, and open woodland plants there.  All of this work is aimed at getting more light to the ground, which should stimulate increased oak regneration and a stronger, more diverse, herbaceous community on the woodland floor.  In addition, we hope that increased light will put shade-loving garlic mustard at a disadvantage, at least in some parts of the woodland.  From talking with others around the country, they’ve seen mixed results from similar work.  I guess since we want that light on the ground anyway, we’re going to forge ahead – and hope we don’t make things worse.

Jack-in-the-pulpit is one of many woodland flower species that help make the Rulo Bluffs Preserve unique and valuable.

Jack-in-the-pulpit is one of many woodland flower species that help make the Rulo Bluffs Preserve unique and valuable.

Finally, we’re pulling garlic mustard because the Rulo Bluffs Preserve is worth the effort.  It’s one of the few remaining high-quality oak woodlands in Nebraska, and hosts a wide diversity of plant and animal species – many living at the edge of their geographic range.  In addition to lots of mayapples, jack-in-the-pulpit plants, and woodland phlox, we also found two orchid species blooming last week – the showy orchid and the yellow lady’s slipper orchid.  We walked around beneath eastern deciduous tree species such as chinkapin oak, black oak, and Ohio buckeye.  Several animal species at the preserve, including zebra swallowtails, timber rattlesnakes, and southern flying squirrels, are only found on the very eastern edge of Nebraska.  While some of those species are common to the east of us, it is probably important to protect their genetic diversity by maintaining populations across their entire range.  That should allow the species to better adapt and survive in changing conditions over time.

Genetic and biological diversity aside, the Rulo Bluffs Preserve is also important because it’s a beautiful place.  We need to keep some aesthetically-pleasing natural areas around for people to enjoy.  Despite our aching backs, Nelson and I had a great time exploring the preserve last week, marveling at warblers, flowers, velvet mites, and other wonders.  It’s possible that we’ll invest a tremendous amount of time and money into stewardship and restoration at the Rulo Bluffs Preserve over the next several years and still lose out to garlic mustard.  There are plenty of examples of that happening elsewhere.  I guess we’re not ready to concede the battle, however – there’s too much at stake.

19 thoughts on “Blowing Against the Wind?

  1. don’t give up!! we have a small township preserve with 2 wooded areas – after 5 years of pulling garlic mustard (some years we did better than others) I think we have turned a corner here – less this year than last year – and the reward is increasing stands of false solomon’s seal, jack in the pulpit, mayapple and others –

    I so enjoy reading your blog – and we learn a lot from you – we have even made a “kill stick” using your directions – because in addition to garlic mustard we have honeysuckle and autumn olive to contend with –

    so good morning from northern ohio – you have lots of company in the garlic mustard wars –

  2. Chris,

    As always, your posts are so much appreciated. We’ve had success dealing with Alliaria in our woodlands by ignoring it and focusing our efforts on correcting the true problems: lack of sunlight due to disrupted fire regime resulting in dense woody vegetation. By thinning the woodlands to admit light amounting to roughly 10% of the ambient sunlight, and utilizing frequent dormant season fire, we are witnessing dramatic improvement in the native flora and even more drastic reduction in Alliaria. Years ago I spent a couple seasons pulling garlic mustard in localized areas and did not observe any improvement – just a lot of soil disturbance. And after all that time and energy expended the woodlands were still languishing from lack of sunlight. I’ve come to the conclusion that Garlic Mustard is a symptom of a larger problem. Rather than treat the runny nose, we’ve decided to treat the root of the problem. There are some non-native species that can be dealt with simply by correcting the processes that shape/influence the system and nurturing the native inhabitants. Garlic Mustard seems to be one of those alien species that can be dealt with in this manner. Other species are more analogous to cancer and need to be treated directly. In my experience those species include crown vetch, canada thistle, Ailanthus, leafy spurge, and more.

    Our natural areas are overwhelmed by an onslaught of non-native and invasive species, but restoring the integrity and resilience of the systems – just as you are doing with your high diversity reconstructions – will solve some of those problems. Keep up the great work and the legacy you leave will be healthy natural areas supporting countless lifeforms and inspiration for many belonging to our species. Thanks so much for sharing all of your insights, challenges, lessons, questions, and humor.

  3. Chris, have you heard of Landcare groups in Australia? That is exactly what you are describing. They have some pretty good ideas on how to motivate volunteers to pull weeds.

  4. I thought I would share my experience with garlic mustard a few hours south of your preserve in Topeka, Ks. For the first time last year I noticed an insect attacking the garlic mustard along the Shunga creek in Topeka. Theses woodlands are invaded by bush honeysuckle and garlic mustard. There is still plenty of garlic mustard, but whatever this insect is, it could be the answer to your controlling garlic mustard.

    • Is the insect you found attacking garlic mustard a small, dark blue aphid? If so, it is probably Lipaphis brassicae or something similar. We noticed this blue aphid on our garlic mustard at Indian Cave SP in southeast Nebraska a couple of years ago, got all excited that it could be a biological control for GM, and then found it had already been studied and was not an effective control. Even severe infestations of the aphid only seem to set back the GM and reduce seed production somewhat, but do not kill it.

  5. In my experience dealing with Allaria: I gave up pulling it about a decade ago. My first option is to burn the woodland, what survives that you spray, what you miss, you pull. I have also seen a decline in its density over the years (in like a lion), so one should remember not to be so alarmed the first few years after invasion.

    Like the comment prior. Normal woodland restoration activities will coincide with an overall reduction.

    Thanks for your excellent blog!

  6. my husband has a degree in forestry; he goes berserk when he sees garlic mustard here. we only have a half acre, but we are trying to get back to an adirondack ecosystem, which this was before all the white pines were cut almost 200 hundred years ago.

    you guys are are working so very hard – please keep doing what you are doing. we are from central illinois, have loved prairie all our lives, especially our tall grass. you are a little bit of home to us, altho we really love new york state, too.

    thank you

  7. Your post stimulated fond memories of my summer working on the Schulenberg prairie at the Morton Arboretum back in the late 80’s and attending after work “botanizing” sessions led by Ray himself. I am sure he would appreciate all of your hard work.

    Dave Sollenberger

  8. Chris, as usual, you rock. Great explanation of why we manage invasives, even when it appears we’re not making progress. A couple things – we do not find that fire and clearing reduce garlic mustard in IN. GM seems to do quite well in the 1/2 shade of a savanna and it is increasingly found around and in farm fields – in full sunlight. This may be because we have more rain in IN, and that allows garlic mustard to survive in these marginal open habitats. We have had burns that knock back the current year’s crop of flowering plants, but generally the next year is worse, as the seed bank takes advantage of the cleared soil. If we could consistently burn the same units every year and repeatedly knock it back, I think it could help – but who can consistently burn every unit every year? Also, severe infestations will not carry fire unless there is really good leaf litter fuel. The green rosettes tend to put the fire out. Bottom line, invasives love disturbance and are often able to capitalize on it before natives.
    A very important issue for us is deer population – we are way beyond carrying capacity in much of Indiana, and garlic mustard appears to be simply invading the areas cleared by deer. To really get the natives back, deer populations have to be reduced (this is true in much of the east, but may not be an issue for you – you may have reasonable numbers of deer there). And lastly – there are HUGE yearly fluctuations in populations unrelated to management. 2012 was the worst GM I’ve ever seen do to a very mild winter (didn’t kill any of the overwintering rosettes), 2013 there’s hardly any (very bad drought seems to have killed many of the first year plants). If we have a severe drought or a bitterly cold winter, 2014 may be a good year- if we have lots of rain and a mild winter, it’ll be GM hell. It makes it very difficult to see long term trends.
    Keep up the good fight – I still have hope for an eventual biocontrol.

    • Thanks Ellen – and thanks for the input as I was putting the post together. It’s been interesting to see the comments here and the others I got via email. There is a wide range of strategies being used and apparently a wide range of (often conflicting) responses to those control strategies from place to place. As per usual with invasive species control, no one strategy is sufficient, and it takes a lot of trial and error to see what works best at a particular site.

  9. Good work! It is a constant battle we fight in Missouri as well. We have found if you can’t beat it, eat it. It was brought to this country by imigrants from Eastern Europe where it is consumed regularly. Unfortunately, its natural predators were left behind.
    Garlic mustard leaves are a great addition to salads or on sandwiches. They are said to be best eaten as the small early rosette leaves, but we find them tasty even when they are trying to go to seed. Some cook with them, a taste we haven’t yet developed.
    Our battles are documented at

  10. I have been controlling garlic mustard since 1991 on several dozen properties with many different plant communities such as woodlands, savannas and grasslands and have yet to see it disappear. The typical scenario that I see repeated over and over is that areas managed for garlic mustard using a combination of control methods are able to maintain healthy ecosystems while the neighboring lands degrade quickly into novel ecosystems. Unfortunately, the mustard control comes at a cost and the control in ongoing year after year. I tell folks to use the garlic mustard control time as a chance to do species inventories as all areas of the property must be checked. Watching lands being consumed by garlic mustard is tragic, but what I have found to be even more tragic is when property managers become overwhelm with the logistics of garlic mustard control and give up on it. Incidentally, I remember talk of biocontrol as far back as the early nineties.


  11. Overall, I totally agree with Ellen and “cedarmeadow” – There’s a lot of evidence that garlic mustard is an opportunist, and readily takes advantage of the disturbance and changes that we’ve caused on the landscape. On the other hand, it certainly seems capable of causing further change in areas it invades.

    I was interested to hear that at least a couple of people have found that Garlic Mustard seems to increase following management. I worked on some removals in central Illinois, and we found that second-year GM plants seem to out-compete GM seedlings. So, removal of established plants actually increased seedling survival, and in the following year, we had more mature GM plants! With continued pulling, the seed bank seems to get depleted and pulling does reduce GM abundance.

    Recovery of native species is fairly slow though. The first response that we noticed was from spring ephemerals – possibly because they’re competing most directly with GM. Over time, the species that increased with removal were all non-mycorrhizal. Which suggests that invasion, even after it’s controlled, has “legacy effects” on the soil. After five years of removals Roger Anderson tested for the abundance of mycorrhizal fungi, and found that they had increased in areas where Garlic Mustard was removed. We don’t have any never-invaded reference areas for this study, so it’d difficult to know if the removal areas are recovering to their pre-invaded condition. However, it does seem like plant and soil communities can respond positively to GM removal – it just takes a lot of work!!!

  12. When I was helping pull garlic mustard here in Illinois a few years ago we were told to put the plant directly into a plastic bag so that the seed wouldn’t be spread. The picture of Nelson above made me a little bit nervous!

    • I agree with the recommendation to bag the garlic mustard and even burn it later. The pulled plant has a remarkable ability to continue to transfer its residual energy into the seeds. Several friends have dramatic stories of leaving a pile of pulled plants or in one case placing a wad in the crotch of a tree, then coming back the next year to find a massive plot of rosettes.
      We religiously bag the pulled plants, then burn them next winter.

  13. Garlic mustard can be controlled by pulling alone. After the first couple of years the amount of work required reduces dramatically. Garlic mustard kills the symbiotic fungi required by most native plants. Interestingly enough, once the garlic mustard has won the battle and eliminated mycorrhizal fungi the garlic mustard stops smelling like garlic. It is best to take a military style clear and hold approach to garlic mustard control. Clear the areas permitted by resources. As garlic mustard is controlled in those areas you will be able to expand to new territory. Over time you will have eliminated garlic mustard from the largest area possible given your resources. It is worth the effort in quality areas. It is also an enjoyable task. It is great to get out into the woods when the spring wildflowers are blooming and the bugs have not yet become a nuisance.

  14. It sounds like the terrain is fairly steep. Garlic mustard seed can be moved downhill by overland flow as well as by streams, so position in the watershed can also be a factor to think about when deciding which populations to target (i.e., scout for and focus on populations that are high in gullies, or that are upslope from pockets of high diversity).


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