the science

studying the Age, Health, history, and genetics of Boulder’s apple trees.


Our remaining apple trees not only hold vast potential to unlock fascinating historical and cultural narratives, they provide genetic resources that convey disease resistance or tolerance to environmental stressors and offer an important potential local food resource. These benefits are particularly strong with apples since you can take a graft of a historic tree and preserve it for future generations in urban orchards, with great potential to provide multiple ecosystem services in the future.


Evaluating diversity, health, and potential

We collect all kinds of data on the trees surveyed in the project. Data that shed light on the age and health of the tree, on the type and flavor of the apples, and the genetic diversity that it offers to future populations. Here we explore some of our primary data types and what we hope to learn.



Our quest for the lost apples of Boulder County has begun. In 2018, we located nearly 300 trees and collected biological data on almost 200 trees. We are building GPS maps, spanning public and private land, to understand where these trees still stand in and around Boulder County. Join our efforts to find and map all of the remaining apple trees.


Age & Health

Old apple trees often have rotting or hollowed trunks so taking core samples for exact tree ring dating is challenging. To get relative tree age estimates, we measure the trunk diameter and use historical information to assign approximates dates to when the cultivars may have been planted. We are also collecting information about insect use of the fruits, state of trunk rot, and symptoms of fireblight, a bacterial disease that can be destructive to the trees.


Fruit flavors & morphology

In the lab, we assess the flavor, shape, texture, and colors of each tree’s apples. We measure the sugar content in the fruits, which is important for their culinary and cider-making potential. We also photograph cross sections of the apples in the US Department of Agriculture style, so we can compare with their reference photos.

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Cultivar identification

Apples are notoriously tricky to identify, as some apples look the same but are different cultivars, while others look very different but are actually the same. We extract DNA from the leaves of the tree, to sequence the genes and compare to the USDA genetic reference collection. The fruit and tree characteristics we’ve collected help us cross-check the genetic identification and learn more about trait variability within a cultivar.


Submit your tree for sampling!


If you have an apple or crabapple tree in your yard or know of one on public property, please submit information about it here! We collect leaf samples (and fruit, if possible) from each of the trees that we sample, to build a database on the genetics, phenology, disease, and age of the trees around town. We are particularly interested in heirloom varieties of apples that were planted on Boulder's early homesteads.


Get involved

We would love your help with ecological research!


join our fall 2019 cure at cu-boulder!

In Fall 2019, we are offering our first CURE for CU-Boulder incoming freshman and transfer students: EBIO 1250. The first round of this course features three research branches that students can choose from: 1) Research on the urban ecology of apple trees including effects of urban heat islands on tree growth, 2) Investigations on the effect of the shifting climate on apple tree phenology and physiology, or 3) Genetic explorations of the basis of fruit characteristics such as sweetness or bitterness. For questions about the course or to enroll, contact Lisa Corwin.


join our bridge program at Front Range Community College!

FRCC students are invited to participate in the first annual Boulder Apple Tree Project bridge program. Students who are accepted into the program will spend the first three weeks in August 2019 working on a research project that seeks to map where historic apple trees are located, determine environmental influences on tree growth, and identify the genetic variety/cultivar of trees. Stipends of $800 will be awarded for 20 hours of engagement/week for 3 weeks (60 hours total) in August 2019. For questions about the program or to apply, contact Lisa Corwin.


Collect your own fruit and leaf samples!

The information you collect about the tree and fruit characteristics will help us identify cultivars and compare fruit ripening among trees. Identifying cultivars is the first step to understanding the diversity of apple trees we have in Boulder and will allow us to explore research questions about how differences in the local environment and climate change may affect these historical trees in our community.


have you Completed a fruit / leaf sample?

drop it off at one of these locations:

INSTAAR main office. Room N202
CU-Boulder East Campus
Sustainability, Energy and Environment Complex

4001 Discovery Drive
Boulder, CO 80303

(303) 492-6387
Monday- Friday 8am-5pm


CU Museum of Natural History front desk
CU-Boulder Main Campus
Henderson Building

15th and Broadway
Boulder, CO, 80309

(303) 492-6892
Monday- Friday 9am-5pm