Tom's Blog

Sunday, December 9, 2012

Controlling prairie willow at Black Earth Retttenmund Prairie

Yesterday our monthly work party at Black Earth Rettenmund focused on controlling the large amount of prairie willow (Salix humilis) that threatens to take over the top of the knoll on the North Unit.

About 8 years ago, when we did major brush work on the North Unit, we left the native prairie willow when removing all the nonnative shrubs. We assumed that because it was native, and had the word "prairie" in its common name, that it should be allowed to remain. At that time there were only a few small clumps. About three years ago we suddenly realized that the willow had spread greatly, and was now starting to shade out prairie forbs and grasses. The biennial burns that should have held it back were not doing their job. Since the North Unit had lots of important prairie species, we decided we needed to control the willow.

Prairie willow grows in clumps with a variable number of stems. (My counts yesterday ranged from 11 to 84 stems.) No rhizomes are formed, so an individual plant is rarely more than a couple of feet wide and about knee-high. I haven't followed individual plants but according to the horticultural literature it is moderately short lived. It flowers early in the spring (the buds are like pussy willows), and spreads by seeds. At Black Earth Rettenmund we have seen it spread widely on the North Unit, but it has not appeared elsewhere at the site.

In May of this year we had a volunteer work party which controlled brush on the North Unit. At that time, prairie willow was the primary target. See this link for details, including growing-season photos. Soon we became occupied with sweet clover control followed by seed collecting and it was only now that we could return to willow. Since we plan to burn the North Unit in the spring, it was important to deal with the willow now.

Yesterday a small but dedicated group of volunteers helped us attack the willow. Some people used hand clippers or loppers, treating the cut stems with Garlon 4 in oil. Because the willow stems are quite thin, the cut stems present very little surface for herbicide, so that the herbicide was used as a basal bark.
Mark working at the top of the North Unit. In the foreground is a large willow plant with over 50 living stems. These clumps can be easily spotted this time of year by the distinct red color of the stems.

 In fact, you don't really need to cut the stems, and at this time of year, when there is no foliage, each stem of a clump can be easily herbicided with the paint sponge technique. The photo below shows this working on a small clump.

Close up of the center of a willow clump. At this time of year, when there is no foliage, it is easy to basal bark stems with the paint sponge stick.


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