Garlic Mustard Seedlings 2011

by Carl Strang

As chance would have it, there are very few patches of second-year garlic mustard plants at Mayslake Forest Preserve this year, and none that will suit the next stage in my experimental study of best methods for manual removal of these invasive European biennials. There are, however, abundant seedlings.

This is a typical scene where garlic mustard is established. Seedlings appear very early in the season.

Last week I paid a final visit to last year’s experimental plots to count seedlings. These are areas, divided into square meter units, in which I either uprooted plants, or clipped them at soil surface level, or left them alone as controls, in April. I have found that uprooting garlic mustard is effective in March or April, and clipping also is effective but surprisingly so in April (practically none survive).

In the process I am looking into the possibility that uprooting plants disturbs the soil and increases seedling germination, a possible negative side effect. Earlier I found that pulling tiny second-year plants in March does not encourage additional seedling germination. Uprooting larger second-year plants in April disturbs the soil more. I found last year that same-year seedling germination is not increased, however. Would the same be true in the following season?

The bottom line answer is, yes. The total number of seedlings in 9 square meters of controls was 6125 (range 262-1444, median 724). Clipped areas produced 5954 seedlings (range 249-1397, median 491). Uprooted squares contained 5595 seedlings (range 150-1286, median 515). Differences were not statistically significant. That puts to rest, in my mind at least, concerns about the common practice of uprooting.

So, I am done I think with hands and knees work. The next stage, which now will need to wait until next year, will be to try clipping with a cutter that allows more efficient, faster removal than one-by-one hand clipping.

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4 Comments

  1. Beth Johnson said,

    April 12, 2011 at 8:18 pm

    I have been spraying the garlic mustard in our woods in March or early April for the last 3 years and we hardly have any new plants this year. I don’t think the Round-up is affecting the other plants, as they do not emerge until later. In fact, we have an amazing crop of new wild flowers that I never noticed before. They were always hidden by the obnoxious garlic mustard.

    • natureinquiries said,

      April 13, 2011 at 5:49 am

      Thanks, Beth,
      That’s a good example of how established populations typically are handled, especially in areas where weeding is impractical because of the volume of garlic mustard. As you point out, the rosettes of garlic mustard that overwinter are vulnerable to herbicides before native plants emerge, and if you are careful with the timing you can get good results. Your response from plants that had been suppressed must be gratifying.

  2. Maria MacWilliams said,

    April 6, 2012 at 8:10 am

    Dear Carl,
    Thank you for the systematic study of clipped vs pulled. I will feel comfortable following either method of removal.
    The photos of garlic mustard seedlings were also quite informative. It has confirmed my speculation that the nice little sprouts coming up in our garlic mustard areas are indeed the progeny of past garlic mustards.

    • natureinquiries said,

      April 10, 2012 at 5:57 am

      Thanks, Maria,
      As a rule of thumb, the effectiveness of clipping increases as the season goes on, but it must be close to the ground. Pulling appears to be better early. In 2012 I’ll be experimenting with mass methods of cutting.
      Regards,
      Carl


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