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Elm trees on the research plot begin life as a cutting from an older elm tree. To get material to make new trees, we prune the old ones. Jonathan, myself, and Lara our volunteer cut off all of the lower branches from one plot of the elms. After taking the branches off, we took them to be processed.

Jonathan, Lara and I are all working our pruning technique. It is as much science as an art form, and to get material to make cuttings from, we are able to practice our cuts. We made a  red permanent marker marking to outline the cut. When removing a limb, the aim is a cut that is perpendicular to the branch. The cut should be as close as possible to the collar of the branch without breaching it. The collar provides a physical and chemical barrier to disease entering the main stem of the tree, and nicking it or the trunk of the tree with a saw is the sure sign of a beginner.

During processing, we removed the new growth from the woody growth from last year. The newer the cutting, the more likely it will sprout roots. We cut the new growth into sections of around 6 inches, or the distance between an extended pinky and thumb (think "hang loose").

After they are in 6 inch pieces, we remove all but two or three leaves from the very top of the cutting. The bottoms of the cuttings are then dipped in a hormone solution that causes the cutting to sprout roots.

Fast forwarding 10 years, the elm trees in the plot are inoculated with Dutch elm disease. This disease wiped out much of the elm population, and now we are working to propagate the most resistant varieties. The trees that prove resistant to the disease are then trimmed down again, and another generation of elm trees is produced.

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Urban forestry and arboriculture has changed quite a bit over the last 100 years.

Many old practices like cavity filling and wound painting are gone for good. Oftentimes, though, we can learn from the old-timers, like Theodore Wirth.

Wirth & Co Photo - Calhoun.jpg

Wirth was appointed Superintendent of Parks in Minneapolis in 1906 and was instrumental in creating this "City of Parks".

In this photo we see Wirth (far left) and other Park Board Commissioners, posing with bare-root American elms.

Fast-forward 100 years to 2010 and we are applying pruning practices from this bygone era to trees in the 21st Century.

Craig - Theo Wirth.JPG

Craig Pinkalla, arborist with the Minneapolis Park & Recreation board, stands next to a Princeton American elm he's just finished pruning at Fort Snelling. 

Since his days maintaining the urban forest in the City of Milwaukee, Craig has been a strong advocate of giving young trees a chance to become mature, productive shade trees. 

In a sense, we've gone "back to the future."



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Chad - Smiley.JPGChad Giblin will be at the 48th annual Minnesota Shade Tree Short Course at Bethel University in Arden Hills, MN on 16 & 17 March 2010 signing his new book Pruning Young Elms and discussing structural pruning techniques for young elms and other popular trees in the urban forest.

Stop by for some great continuing education for arborists, urban foresters, and tree advocates.  A copy of Chad's book is included in the registration price for the Short Course.







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