Garlic Mustard Study: Final Spring Results

by Carl Strang

One of my studies this spring has been an experimental comparison of removal techniques for garlic mustard, an invasive biennial that poses problems in our woodlands because it inhibits the growth of all other plants (including trees).

GM bolting b

A month ago I removed all the second-year plants from my study plots. As I reported then, it was clear that pulling the plants in March was more effective than was cutting them off at ground level, though both treatments killed most of the plants. In the following photo you can see an example of new side shoots springing up from where the main stem had been clipped.

GM clipped recovering b

In that May treatment I also clipped the control plants at ground level. After waiting four weeks I recently returned to see whether any second-year plants had recovered to send up new stalks. I also wanted to check progress of seedlings, which had been suppressed by the control plants but had been growing vigorously in treatment areas.

The results again were impressive. All but 6 of the 1482 control plants (99.6%) were killed by the May clipping treatment, in contrast to clipping in March. None of the few survivors of the pull treatment that I cut in May survived. More (17) second-year plants survived their second clipping.

GM 15JE 1b

At the moment it appears that early pulling and late clipping both are effective techniques, but I have more tests to do next year. The jury still is out on the question of whether (or under what conditions) pulling may increase germination from the seed bank in the soil.

After a month the seedlings in the control squares still were far from making up the ground they lost in comparison to seedlings in treatment squares.

GM 15JE 3b

The next step in this study will be a return to count the seedlings in the fall. I am interested in how much they thin themselves through competition with one another.

%d bloggers like this: