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It’s an important task to manage Gambel oak because of the fire risk. These trees are ignitable and burn really hot.

If you live in the foothills, you probably have Gambel oak, aka scrub oak (Quercus gambelii), in your landscape. This native tree has some great attributes and some big management challenges.

Good qualities of this tree is that it is native, drought-tolerant, resilient and provides shelter and food for wildlife, including larval food for butterflies.

The downside of these trees includes fire risk: They are ignitable and burn really hot. The thicket- forming growth habit can be unsightly. While they are rarely killed by disease or insects, they often become disfigured and unattractive due to these problems. Dead branches increase fire risk. Unlike other oaks, they really do not form a broad canopy, probably because they naturally grow in thickets, where they are more of an upright shrub form. There is lateral branching, but as they grow taller the canopy does not expand proportionally.

Control of these trees is challenging. The thicket habit is the result of an extraordinary ability of these trees to produce new sprouts from the trunk of the trees, the roots and some intermediate rhizome like segments of roots. All three of these sites contain adventitious buds; growth areas which are not directly on the stem (trunk) of the plant. If you dig out the trunk of a Gambel oak you will find numerous adventitious buds starting a few inches below the soil, and occurring as deep as 3 feet deep. That is why if you cut the tree down, or it burns down, you will see new growth very quickly, perhaps within 10 days after a fire. These trees really know how to come back! You will see this new growth around the trees even with the main tree in place. In addition, the roots have clusters of these buds; unlike many trees that require sunlight to trigger new growth, these buds will sprout up between established trees.

For fire management purposes, you can control these trees by mechanical means — pruning and thinning. However, this is an ongoing task; you will be doing it every year. If you find the trees desirable, make sure they are limbed up to the lesser of 10 feet or 1/3 of the height of the tree. The trees should be no closer than 15 feet from structures; 30 feet is preferable. For urban locations, tree should be thinned to 10 feet apart.

Chemical controls are available. If you are removing trees, you can apply herbicides such as glyphosate or triclopyr directly to the stumps immediately after they are cut. Follow label instructions. Be aware that neighboring Gambel oak trees will likely be damaged because of shared root systems. To control sprouts, more- dilute foliar applications of these products may help control sprouting, but may also damage neighboring trees. More discouraging, it might not control new sprouts at all. Both of these products work through the root system of the plant they are applied to. They are not soil active, so will not negatively other plants in the area.

Love them or hate them, but make sure these trees don’t increase the risk of your home burning.

Submit gardening questions to csumg2@elpasoco.com or call 719-520-7684. The in-person help desk is open 9 a.m.-noon and 1-4 p.m. Mondays and Wednesdays at 17 N. Spruce St. Find us on Facebook at Colorado Master Gardeners — El Paso County.

Submit gardening questions to csumg2@elpasoco.com or call 719-520-7684. The in-person help desk is open 9 a.m.-noon and 1-4 p.m. Mondays and Wednesdays at 17 N. Spruce St. Find us on Facebook at Colorado Master Gardeners — El Paso County.

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