Catching up to the 21st century, part 11...scotch broom

Scotch broom is a perennial leguminous shrub that is considered an invasive species in California. If left unmanaged, it can quickly take over a land area. Every year in spring, we practice the ritual of "pulling broom" to keep it under control. We pull in spring because the soil is loosened up from rain, making easier work.

I have questioned the effectiveness of pulling because the scotch broom always reappears. I have heard that there can be an 80 year supply of seeds in the soil around plants that have been freely reproducing year after year. Pulling one of these plants exposes seeds that were buried in the soil around the roots. These seeds germinate in the disturbed soil resulting in another patch of scotch broom next year.

I decided to try an experiment comparing pulling to cutting. In the middle of February, 2007, we pulled waist-high scotch broom west of a north to south running landmark. We cut broom east of this landmark. The nice thing about cutting is that it is quicker and requires less effort. The before and after photos are shown below. Notice how the orange road safety cone came into view - yes it was there before removal.

Before Removal

After Removal

Flash forward to February of 2008. The verdict? In this case, the pulled broom side had fewer plants of smaller size than the cut broom side. I guess you get out what you put in. Cutting takes less effort in a given year, but requires the same - or possibly more - effort year after year. Pulling requires significantly more effort the first year. However, in my experience, it looks like the effort will taper off with continued maintenance.

Thanks for reading. Let me know if you have a scotch broom or other invasive species story.