Tom's Blog

Thursday, February 23, 2012

Dealing with invasive willows in a wetland

Although our wetland is high quality, it is hard to get it burned on a regular schedule (F & WS burned it in 2005 and 2010), which means that invasive plants like willows are able to gain a foothold. Although our principal focus is on savanna and prairie restoration, we hate to see our wetlands deteriorate. With the cold weather and lack of snow, this seems like a good time to deal with some of the willows.

This week we have been using the basal bark technique with Garlon 4 to kill scattered willows. This is probably the cheapest method. Labor cost is low since it avoids cutting, stacking, and burning. Although the dead willows will remain, they will rot away in a year or two.

With the temperature down into the 20s F at night, and no higher than 35 F in the day, footing on the frozen ground is fairly good although we have to avoid getting into any areas of upwelling ground water.

We seem to have two kinds of invasive willows, shrub-like and tree-like. The shrubby willows are scattered (see photo) and are fairly easy to deal with. In fact, many of the older stems are dead and do not need to be treated. The trick is to get the spray nozzle into the center of the bush, and be sure to spray both sides of each stem.
The tree-like willows are fairly small in size, but fiercely clonal and tend to take over a whole wetland. There are some areas along Wisconsin 78 by Vermont Creek that are completely covered with 6-10 foot high trees. We have a few (fortunately small) clones of this type, as can be seen in the background in the photo below.

The basal bark method is not the way to deal with these. If the access permits, a forestry mower would be the best approach, although treating all the cut stems would be impossible. Better might be to return after mowing in early summer and spray all the resprouts with Garlon 3A.

This year we are only dealing with the scattered willow shrubs. We'll see about next year!


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