Mullein expands even more rapidly because it grows well in the disturbed site left behind. Staff clips seed heads from plants. Mullein quickly grows two new seed heads to replace each lost one. Staff cuts the plant's stalk where it joins the root with a spade or applies a herbicide directly to the mullein. Mullein sprouts the following year from seeds that remain viable for up to fifty years.
Staff analyzes the results of their efforts for the last three years.
No headway has been made in eradicating the mullein. The National Park Service is still trying to prevent the spread of mullein into new areas, but it is a daunting task which will require concerted effort over a long period of time. Although complete eradication is likely impossible, the monument is having some success eliminating mullein along the highway corridor. The starling and sparrow, both introduced from Europe, compete aggressively with native birds for the limited nesting holes in trees. If the number of starlings and house sparrows continues to grow, native cavity nesters like the bluebird may be severely affected.