Tom's Blog

Monday, August 23, 2010

Sumac clone out of control

Driving in rural Dane County west of Verona, Kathie and I were stunned to see several old fields that were being taken over by sumac. The photo here shows a "classic" growth pattern of a clone that has been allowed to spread unchecked. The field is obviously mowed, but one imagines that as the clone spreads further, the mower keeps giving it more room.

There is another sumac clone just out of the photo to the right, which is being blocked from coalescing with this one by a clone of Canada goldenrod in the middle.

In the foreground is a substantial roadside population of sumac, and in the background left is another large sumac clone spreading down the hill.

Nearby was another old field that is now solid sumac.

This area along Messerschmidt Road would make a great research site for someone interested in clonal growth of invasive species.

Note the shape of the clone, with taller (older) plants in the center and shorter ones on the periphery. This form agrees with the sumac clonal structure described in detail in 1966 by Elizabeth Gilbert of Oberlin College (American Midland Naturalist 75: 432-445). She studied thirteen clones of Rhus glabra in Washtenaw County, Michigan, and found clones ranging from one to 15 years old, with the mean age of stems in different clones ranging from 2.4 to 7.6 years. The tallest stems were the oldest. Her largest clone was 66 X 120 feet, and the average annual rate of horizontal spread was about 20 feet per year. Excavations showed that rhizomes could extend nearly 12 feet beyond the apparent boundary of the clone. (See her paper for many more fascinating details.)


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