At a Glance
Height: 8-30 feet (usually around 15 feet)
Spread: 6-15 feet
Shape: Sprawling shrub or thicket
Exposure: Full sun
Leaves: Shiny green leaves with 3 to 4 lobes on each side of the vein, about 5 inches long. The leaves turn yellow or reddish-brown in fall.
Fruit: Acorns in late summer
Firewise? No. Scrub oak can be a fire hazard. However, this type of tree is one of the first to reappear after fire thanks to sprouting roots.
Bark: Red-brown to gray, furrows or grooves on older trees
Where to Plant: Hillsides with rocky, alkaline soil where competition from other plants or trees is limited. Best used as a mass planting, such as for blocking a view. Not a good option for a street tree.
Common Problems & Possible Causes
No common issues – Do not overwater; supplemental irrigation is usually not needed unless drought conditions exist.
About Scrub Oaks
Scrub oak, or Gambel oak, can be grown as a shrub or a small tree in Colorado. It is also known as Colorado scrub oak or Rocky Mountain white oak. Although if well-watered it can reach up to 35 feet tall, it often only reaches heights of 15 feet. While oaks on the east coast can grow to be large and imposing, scrub oaks, the only oak trees native to Colorado, stay small and mighty. This allows them to survive harsh winters, dry summers, and wildfires, and their small size means that they can endure strong winds and heavy snow loads. Scrub oaks are incredibly drought-tolerant trees and are one of the first to sprout up again after a wildfire.
Gambel oaks are similar to aspen trees in that they grow from one underground root system. This shrub/tree produces acorns that can germinate to create a new tree, but it more commonly reproduces by sending up shoots from the roots.
Many types of wildlife rely on scrub oak acorns for food, including squirrels, chipmunks, deer, wild turkeys, and even bears. However, the plant itself is toxic. If you’ve heard of cattle or sheep becoming sick from eating scrub oaks, it’s because of tannic acid in the tree’s shoots. If more than 50% of the animal’s diet is made up of Gambel oak shoots, poisoning can occur. It becomes even more toxic if young foliage turns black after a freeze. The acorns are edible to humans once the tannic acid is removed and was a popular ingredient in Native American cooking.
You can spot Gambel oaks in the wild by the thicket of trees that grow together. When destroyed by fire or by browsing wildlife, they often grow again even stronger than before.
The wood is sturdy and is often used for firewood. The twisting or bent form of the branches allows heavy snow to rest on the limbs without much chance of breakage.
In the fall, the scrub oak’s foliage turns bright orange and can often be seen covering the side of mountains or hills. When covering a wide area like that, it is possible that all of the trees share an underground root system and are in fact part of the same organism.
Because these trees can grow together in thickets, they can become a fire hazard. Regular pruning and maintenance can remove some of the branches for a more fire-wise landscape. Dead, damaged, or diseased branches should be pruned out as needed.
You can view some photos of Gambel oak here >>
We recommend spring or early fall planting to get your new trees off to a great start. You can always call us for advice on where to plant your new tree(s) and don’t forget that we offer professional tree planting services if you don’t want to do it yourself!
Recommended Trees & Shrubs
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