Culturally Modified Trees at Great Sand Dunes

A female Native park ranger touches the peeled area of a ponderosa pine in front of the dunes
A park ranger touches the peeled area of a 500+ year old ponderosa pine near the dunes. This tree was peeled by a regional tribe in the early 1800s.

NPS/Patrick Myers

Hidden among the woodlands and forests of Great Sand Dunes National Park and Preserve are unique living artifacts - trees that were modified by generations of Native peoples. On trees still alive today, this modification is visible through distinct peeled areas left behind on ponderosa pines. The purpose of this peeling is to remove the bark from the tree and use it as a resource. Uses for the outer bark include building materials, cradleboards, or trays. The sap or pitch from the tree is traditionally used medicinally, for waterproofing baskets, and as an adhesive. However, the focus of this resource is to use the inner bark of the pine as food and medicine.

At least 200 culturally modified trees have been identified throughout the park and preserve. In 2000, a concentrated grove of 72 modified ponderosa pines just east of the dunefield was added to the National Register of Historic Places as 'Indian Grove'. The National Register of Historic Places is a list of places with significance to American history that are worthy of preservation. With the National Historic Preservation Act of 1966, the National Register was created to protect and preserve these special places. The requirements for National Register designation are a 50-year age minimum and proof that the place has exceptional significance in American history. Living things, such as trees, do not often make the register because many do not meet the age minimum, nor do they retain evidence of human alteration. The modified ponderosa pines within Indian Grove bear this human-altered evidence, or cultural modification, and are up to 500+ years old today.

In the 1996 photo at left, Alden Naranjo stands with a park ranger and archeologist in front of a modified tree; the same photo was repeated in 2016 with Alden's daughter Cassandra
The first image, taken in 1996, features Resource Management Program Manager Fred Bunch, Southern Ute Elder Alden Naranjo, and Archeologist Marilyn Martorano in front of a peeled tree in Indian Grove. The second image, taken in 2016, features Alden's daughter Cassandra with Bunch and Martorano.


The inner bark, or cambium layer, of various pines and firs is highly nutritious, containing calcium, vitamin C, and antioxidant properties. Ponderosa pine bark is full of vitamins, minerals, and vital nutrients that have traditionally sustained Native American tribes. Additionally, ponderosa pines smell strongly of vanilla or butterscotch in the spring and summertime, which means their inner bark also tastes sweet. Historically, these trees were often peeled annually by Indigenous groups for their sweet taste and nutritious value. Springtime was the best time to peel the trees because sap is running through the tree and new growth is taking place, making it easier to peel the outer bark layers off. Southern Ute Tribal Elder, Alden Naranjo, described the peeling process saying “they [his ancestors] would cut the bark, make a line across it, then they would take a piece of wood and peel it from the bottom pulling it [the outer bark] apart [from the tree].”

Once the outer bark is removed, Native peoples scrape the inner bark off the outer bark slabs and either eat it raw or save it for later use. Inner bark can be ground into flour to make bread, boiled in a tea to cure upset stomachs, or saved in strips to be eaten with salt. Based on those who have tasted the inner bark of a ponderosa pine, the taste and consistency is described to be most like eating raw cane sugar. While the bark is not as sweet as the processed sugar we eat today, like in candy bars or cookies, it has a sweet element and was historically a treat for people to go out and peel the trees each spring.

A visitor center exhibit featuring an actual ponderosa pine peeled by tribes with an interpretive panel in front of it
In the lobby of the Great Sand Dunes Visitor Center, one of these peeled trees has been preserved in an exhibit for visitors to view. Nearby is a panel that displays all the names and emblems of the tribes affiliated with Great Sand Dunes National Park and Preserve.


It is hypothesized that the modified trees at Indian Grove were primarily peeled by Indigenous people because of the groundbreaking research done by archeologist Marilyn Martorano. She was able to determine the peel dates of the trees through dendrochronological analysis, which is the science of tree ring dating. She determined that the trees were peeled from 1777 to the early 1900s with the majority of peel dates taking place from 1820-1879. Based on historical research, there were many Indigenous groups inhabiting the area at this time. After consultation with tribal members, they confirmed that their ancestors peeled trees in the area.

According to Alden Naranjo, the Capote band of Utes were the ones who camped in the area where Indian Grove is located, and it is likely that they could have been the people who peeled the trees. However, it could have been any Native American group as many traditionally practice peeling trees and have deep cultural roots to the San Luis Valley and the dunes themselves including Jicarilla Apache, Navajo Nation, and Puebloan peoples. There is a noticeable drop off in peeling activity after 1879. This is because gold and silver were discovered in the San Juan mountains and in the 1880s the U.S. government began relocating Native American tribes to reservations outside of the San Luis Valley. While tribal members would occasionally travel back to peel trees, this was not often and eventually the practice here stopped altogether.

Many of the peeled trees at Indian Grove and found throughout the park and preserve are only peeled on one side. There are only a few instances where a tree was peeled more than once or all the way around. If all the outer bark is stripped from the tree, it would be unable to protect itself and it would die. When a tree is peeled, it produces something called rosin which is a sap that coats and hardens over the scar. This acts like a scab that protects the peeled area and keeps insects out of the tree. While this rosin coating is not as effective at protecting the tree as the outer bark layer, it does a pretty good job. Therefore, the tree is able to live for many years after it has been peeled and continues to grow around the peel which is why many of the trees in Indian Grove continue to live today.

Indigenous peoples know that if they peel the whole tree, it will die. Therefore, they only traditionally take as much as they need, and historically left most of the trees living for many years after the peeling event. Since trees are a non-renewable resource, meaning they cannot be replaced as fast as people eat them, why would they not take the whole tree? The reason these trees were intentionally left living is because Indigenous people have a lot of respect for them and the greater purpose they hold. Trees are homes to animals, provide shade, keep the air clean, and are essential pieces to the ecosystem. Native peoples historically relied on the land to sustain them, and they understand the important role trees play in keeping the forest healthy. If you take away the trees, then there will be no forest left to live in. Therefore, the Indigenous ancestors only took what they needed and left the trees living to finish their job and keep the ecosystem strong and healthy for the next generation of people.

Today these peeled trees continue to thrive here at Great Sand Dunes National Park and Preserve as living artifacts that connect modern tribal members to their ancestors and traditions. The National Park Service continues to partner with Native American tribes to protect these living artifacts and continue the mission of the Native Americans who first peeled them by allowing them to live out their natural life cycles. The landscape that these trees live in has seen little change since the days when Native Americans first encountered it and will only continue to remain this way if we all work together to protect it. Therefore, we ask that you practice Leave No Trace protocols, not just at national parks, but at all the places you visit, so that future generations can come and enjoy the places we love so much.

Last updated: December 6, 2023

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