Garlic Mustard Follow-up

by Carl Strang

I have a final bit of data to share for this year in my study of garlic mustard removal methods. I returned to this year’s study plots in September to see how much the seedlings had thinned out over the summer. Thinning always occurs, as various mortality factors (including competition among the seedlings themselves) take their toll. I did not expect the dramatic degree of thinning I observed, however.

The bare soil you see in this study plot corner was typical. Median counts were 0 seedlings in the square-meter plots for pulled treatments, clipped treatments and controls. Totals in the 9 square meters for each category were 17 seedlings in clipped squares, 4 in pulled squares, 5 in controls.

That compares to respective totals in May, the last time I counted seedlings, of 700, 609, and 575. I should say that this is a different result than I saw last year. Last year’s May totals were 1002, 747 and 214. Last year’s end-of-season totals were 107, 236, and 3. The two years had much different weather, so I cannot say that this difference is due to the year, to the slightly different plot locations, or to the difference in treatments (treatments applied in March 2009, April 2010). On the other hand, the controls produced similar results in the two years.

The only data I neglected to report last spring, by the way, were the over-winter survival numbers of those end-of-season first year plants. The respective totals were 97 plants in clipped treatment squares, 226 in pulled treatments, and 4 in controls (obviously I missed one the previous fall). Over-winter survival thus was good in all three cases; the main thinning occurs during that first growing season.

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