Keys to Crown Reduction by Trees Are Key published on 2019-05-16T15:56:48Z Trees Are Key Let’s discuss "Keys to Crown Reduction." Crown reduction may be one of the more challenging pruning objectives. Most of this work should be done in the outer canopy of the tree and is a skill. Listen in to learn more! Species Spotlight The Blackjack Oak, Quercus marilandica, is less commonly known as Barren Oak, Jack Oak, and Black Oak in Texas. The range of the Blackjack Oak is from East Texas all the way to Central Texas, with a small distinction on the western side.