Savanna & Trails

Robert Grau Memorial Savanna

The Robert Grau Memorial Savanna is located on the ridge north of the cooperage at Motor Mill.  Robert Grau was a charter member of the Clayton County Conservation Board and enjoyed spending time outdoors in both woodlands and prairies.

The Grau family approached the Conservation Board about a memorial project at a time when the Conservation Board wanted to recreate the mid-1800’s historic oak savanna landscape at Motor Mill.  Thus a strong working partnership began.

In early 2005, the project began by removing the smaller trees from the ridge top and leaving only the dominant bur, white and red oak and walnut trees.  The open canopy has now allowed more sunlight to reach the forest floor and has promoted the resurgence of native prairie plant species.

What is a Savanna?

An oak savanna is made up of scattered oak trees above a layer of prairie grasses and forbs.  The trees’ spacing allows sunlight to reach the prairie plants below.  These rare plant communities once covered 10% of Iowa’s landscape.  Fire frequently swept through these areas and was critical in maintaining this ecosystem.

Managing with Fire

Prescribed burns are conducted periodically as a way to manage the area. The burns occur in the spring after the snow has melted and before the forest floor has greened up with new spring growth. The timing is important as the fire serves several purposes. One is to keep the forest floor open, two is to promote native plant growth and three is to help control weedy vegetation on the site.

One of the main “weeds” being controlled is a very aggressive non-native invasive plant called garlic mustard. Several methods of control are being used including fire, chemical and hand pulling.



Currently a trail system takes visitors up to the top of the savanna and by the rock quarry used in the construction of the limestone buildings. Recent plans expanded the trail system through the north end of the park.

Come out to Motor Mill and walk the trail! Make sure you have good walking shoes as the trail to the top is rather steep. Be sure to give yourself plenty of time to enjoy the sights and sounds of the Robert Grau Memorial Savanna.

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