Eagle Creek Park Big Tree Registry

EAGLE CREEK PARK BIG TREE REGISTRY
October 2026

Welcome to the Eagle Creek Park Big Tree Registry, a volunteer science project to inventory and catalog information about lone big trees and family groves of big trees in the Park. The term “big tree” implies that a tree is large in width and usually tall in height relative to other trees in Eagle Creek Park. Big trees are uncommon in Eagle Creek Park.

Historically, Eagle Creek Park land, like most of Indiana, was covered by forest. The original old-growth trees were removed during early settlement. A century ago, this part of Marion County included old farms, rural homesteads, and private estates. In many places, the second-growth forest that emerged after the old-growth trees, also was removed. The history and mixed management of the pre-Eagle Creek Park land created locations where some lone old-growth trees or groves of second-growth forest were isolated, or ignored, or intentionally preserved. Big trees are among the oldest members of their species in the Park. These trees have survived because of inherited fitness, a healthy environment, and a safe location.

The Big Tree Registry is a catalog of information about trees that are big among all tree species and big for their species. The catalog was derived from an ongoing inventory of trees in the Park. The purpose of the registry is to communicate and educate park patrons, park staff, and park advocates about the natural history and human history value of preserving our big trees.

Big tree inventory data were collected annually since 2020, continuing through 2026. The inventory involved scouting and measuring apparently large trees along trails and roads as well in areas without trails or roads. Tree trunk size and general location information were noted in the inventory, often in winter when large tree trunks were more visible. The inventory was in Park land north of 56th St.—1,275 acres on the east side and 955 acres on the west sides of Eagle Creek Reservoir, including the Golf Course. Inventory data was recorded in a field notebook.

Big tree registry data were collected for selected trees found during the inventory. Criteria for data collection initially was a tree trunk girth of approximately 10 feet at chest height. Two adults can face against a 10-feet girth tree trunk and reach around the trunk to touch each other’s hands. The largest trees in the Park require 6 adults holding hands to span the girth. Field data include tree location, tree species, tree trunk girth, tree height, and tree shape, documented with specimens and photos. Field methods were consistent with those established by the Eastern Native Tree Society and vetted by numerous university forestry department faculty. Field data were combined with field notes and calculations, all entered in a digital data-base catalog which is a multi-tab spreadsheet with 38 columns of information per tree. 

Tree location was established with a handheld GPS (global positioning system). Latitude north and longitude west were recorded in degrees and decimal feet to 5 significant figures.

Mapped location for each tree includes a Google Earth position represented by a symbol color coded to the tree species, along with a unique ID. The ID is comprised of two letters representing a part of the Park and two numbers assigned sequentially to trees in that part of the Park. The big tree registry is organized by ID. Mapped location images have the symbol and ID for each tree and can be masked to show only select trees by using Google Earth.

Tree species were determined by comparing leaves, branches, buds, bark, and fruits or nuts to several published references. Voucher specimens of leaves and nuts were collected for select species. As needed, specimens were measured to verify species according to references. Photos of tree leaves, trunk shape, and tree bark also supported species identification for each tree.

Tree trunk girth is the circumference of the trunk 4.5 feet above land surface and was measured with a forestry tape in decimal feet. Circumference is preferred because most tree trunks are irregular rather than circular in cross section and diameter only applies to a circle. Decimal feet is preferred to inches because it has fewer digits to record and compare. Feet also are used for tree height. Girth is measured to the nearest 0.1 foot. Trees on a slope had girth measured from the midpoint of the slope.

Tree shape listed the number of stems (trunks) above the 4.5 feet girth measurement. Multi-stem trees with a single trunk below 4.5 feet were considered a single tree. In addition, field notes list a lone tree or a grove of the same species, tree health condition, and trees with a root base wider than the trunk.

Tree height in feet to the topmost limbs was determined from a distance by use of a laser range finder that includes a clinometer function to calculate height geometrically with three measurements. Multiple height determinations were averaged to attain the recorded height.

A photo gallery is part of the big tree registry and includes at least 5 photos of each tree, recording the GPS screen, the girth tape measurement, tree trunk bark, leaf or fruit specimens, and full view (often with a person in the photo for proportion).

Tree age is a calculated value estimated for the purposes of the big tree registry by use of a common method based on a species-specific growth rate factor. The growth rate factor assumes a constant linear relation between time and girth, and provides the number of years per inch increase in diameter. In the application here, tree girth was converted from feet to inches and divided by 3.14 (pi) to obtain an assumed diameter that was multiplied by the growth rate factor to obtain estimated tree age in years. Growth rate factors vary among tree species, from a fast growth rate (smaller factor) or slow growth rate (larger factor). The relation can be shown by comparing ages of different tree species that each measure 10 feet (120 inches) in circumference (girth), which is 38.2 inches in  diameter. The range of estimated ages varies threefold.

Uncertainty in tree age should be recognized. Tree ages listed are approximate and provide a point of comparison for the trees in the registry. Actually, tree growth rates are not constant or linear and they vary by location. Trees generally grow faster in height when they are seedlings and add girth once they are established. A tree in a dense forest competes with other vegetation for light and water and nutrients and may not achieve the same size as a similar tree growing alone with comparatively less competition. Locations vary in their availability of water, nutrients, and light. Yearly growth varies depending on seasonal moisture and local climate.
Tree age can be physically measured by one of two methods that involves counting the annual growth rings in a cross section from the center to near the outside edge. A sample core can be extracted from the tree with a hollow drill and the core examined under magnification to count rings. A tree that was cut down can have a cross section slice examined and the annual growth rings counted. For the Eagle Creek Park big tree registry, drilled cores or cross sections were not used to measure tree age. Until those data are collected, tree ages in this registry should be viewed as approximate.

Champion trees in Eagle Creek Park east and west of the reservoir and north of 56th St. have been identified in the big tree registry. They are the largest in girth in the Park among all species and the largest among all trees of the same species. There can be more than one champion of a specific species because they are similar in size. Just as there are gold, silver, and bronze Olympic medals but all the medalists are champions, there are some tree species with multiple champions. In contrast, there are many species with only a single champion. On the east side, starting in 2023, champion trees were protected with printed signs on a wooden monument if they were near a road or parking area. Other champion trees along trails may have a sign on a monument. These champion trees were “released” by removing invasive vines from the trunk and removing invasive shrub species and woody debris around the trunk. The trail-accessible trees that are “off-trail” also received a rough access trail. Signs are titled “Eagle Creek Park Big Tree Registry Champion Tree” and list the ID, common name, scientific name, girth at time of measurement, and approximate age at time of measurement. The girth and age are not constant. The date of measurement is in the registry data base. Some champion trees do not have a monument. Some champion trees are not larger than 10 feet in girth but they are the largest of their species. See table 1 and figure 1 for information about champion trees in the Park east of the reservoir.

Acknowledgements: The Big Tree Registry is a volunteer effort to encourage appreciation and protection of big trees in the Park with education and knowledge. Private donations to the Eagle Creek Park Foundation provided the signs for champion trees.

Disclaimer: The science, terms, names, and views stated here are not intended to represent those of the City of Indianapolis, the Department of Parks and Recreation, Eagle Creek Park, or the Eagle Creek Park Foundation. Martin Risch is the author of the Big Tree Registry.

Table 1. Champion trees in Eagle Creek Park east of the reservoir

[OC, Ornithology Center; LL, Lilly Lake; WP, Walnut Point; ED, earth Discovery Center; MP, Mount Pleasant; SP, Spring Pond]

Figure 1. Map of champion trees in Eagle Creek Park east of the reservoir