Natural Areas Management Team Tackles Sweet Clover

Natural Areas Management Team Tackles Sweet Clover

By Chad Graeve, Natural Resource Specialist
Invasive species are getting increased attention and awareness within conservation circles and the general public.  Recently Governor Branstad declared June “Invasive Species Awareness Month” in Iowa.  Here at Hitchcock Nature Center we have identified 101 non-native plant species, of those about 15 of those warrant control efforts.  The others are easily dealt with not by targeting them directly, but by nurturing the native system.  A healthy native system is resilient enough to fend off most of the non-natives, so we are very selective in deciding which non-native species to target.Rich Wehmeyer, crew leader for the Loess Hills crew for the Conservation Corp of Iowa cuts sweet clover at Hitchcock Nature Center.

Rich Wehmeyer, crew leader for the Loess Hills crew for the Conservation Corp of Iowa cuts sweet clover at Hitchcock Nature Center.

Melilotus officinalis Photo By AnRo0002 - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=33379726

Melilotus officinalis Photo By AnRo0002 – Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=33379726

Six years ago we decided to engage in an effort to control sweet clover in our area, an invasive species in grasslands and tall grass prairies.  There are two species of sweet clover, Melilotus officinalis (Yellow Sweet Clover) and Melilotus albus (White Sweet Clover).  The yellow sweet clover begins blooming 2-3 weeks earlier than the white.  Both are biennial plants, which means they grow for two years, flowering and producing seed in the second year.  They can form dense stands that outcompete the native vegetation and degrade the prairie.  The plants are from the Eurasian steppes and are a fire adapted species that thrives in a mid-continental grassland system so fire stimulates germination of the seed.  Because it is so competitive and well adapted to our grassland system, and because it has been widely planted in roadsides and for honey bees, it is a problem throughout the Midwest.  Most conservation organizations that are responsible for managing natural areas choose to ignore it because it is so prevalent and seems to be an insurmountable challenge.  We believe it is possible to control with persistent and thorough hard work.
The crew prepares to scatter the prairies of Hitchcock Nature Center in search of the elusive sweet clover.  There is a tremendous amount of work, focus, sweat, and body fatigue that comes with this effort.  Thank you to the Conservation Corp of Iowa, interns, and staff for all of the hard work.

The crew prepares to scatter the prairies of Hitchcock Nature Center in search of the elusive sweet clover. There is a tremendous amount of work, focus, sweat, and body fatigue that comes with this effort. Thank you to the Conservation Corp of Iowa, interns, and staff for all of the hard work.

Melilotus albus Photo By No machine-readable author provided. Bogdan assumed (based on copyright claims). - No machine-readable source provided. Own work assumed (based on copyright claims)., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=248344

Melilotus albus Photo By No machine-readable author provided. Bogdan assumed (based on copyright claims). – No machine-readable source provided. Own work assumed (based on copyright claims)., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=248344

Since 2010 we have been methodically working at Hitchcock Nature Center to control sweet clover by cutting it when it is flowering to eliminate the seed.  This coupled with our annual fire regime – which stimulates the seed to germinate – will exhaust the seed bank and eventually eliminate (nearly) the plant.  This strategy requires very thorough and persistent control efforts and takes an incredible amount of effort which is physically and mentally taxing.  We have been very fortunate to have tremendous assistance from dedicated full time staff, from hard working seasonal employees, and from the Conservation Corps of Iowa, and The Nature Conservancy.  Our efforts are paying off.  On Monday, Thad Pothast (Conservation Technician) snapped a before photo that illustrates the impact of 6 years of effort.  On the left hand side of the fence is private property that is not managed.  On the right hand side is our property where we use regular prescribed fire and we control sweet clover.  The density of the plants on the private property is exactly what we used to see at Hitchcock in our remnant prairies and in our reconstructed prairies.  Thad took the photo before any treatment this year.  I think the photo speaks to the effectiveness of our treatments and demonstrates that it is possible and worthwhile to address these invasive species for the benefit of the native biodiversity.
photo

Left side of the fence is untreated property. On the right hand side is property managed by our NAM staff to control sweet clover.