Bennett Juniper

The Bennett Juniper is the largest known juniper tree in America. It is located on a privately owned nature preserve within Stanislaus National Forest in Tuolumne County, California. Its height is 78 feet with an average crown spread of 56 feet. The diameter at breast height (4.5 feet above ground) is 12.7 feet. This gives it a total of 573 points by the American Forests formula for measuring “Big Trees” and determining the champion.

The Type of Species

Originally the Bennett was considered to be a western juniper (Juniperus occidentalis). Over time the differences between the northern and southern populations of western junipers justified dividing them into two subspecies and the Bennett is in the southern population which was named Juniperus occidentalis australis. A field guide published by UC Press in 2001 gives the common name Mountain Juniper for the australis population. DNA studies (2006) by Adams resulted in the southern population being raised to species status and it was given the common name “grand juniper” (Juniperus grandis). This name and status is recognized in the USDA Plant Database.

The Age of the Specimen

The age of the Bennett has been an enigma and the subject of varied attempts to determine the age. As reported in Madroño the tree was cored in the 1930s by Glock and he estimated the age as about 3,000 years old. The tree was cored again in 1989 by Peter Brown from the University of Arizona Tree Ring Lab at the request of the current owners of the Bennett, Save-the-Redwoods League. His estimate based on a short sample was the age was also almost 3,000 years. During this coring it was discovered that rotten wood was reached about 2 feet into the tree and that the tree was also partially hollow. As a result there will never be a definitive result from a complete core sample.

The steward of the Bennett, Ken Brunges, suggested a novel method for refining the age estimate. He had noted that the marmot (Marmota flaviventris) living within the tree commonly drags out pieces of rotten heartwood from underneath the tree. The idea was to have it Carbon14 tested as that might provide a provable minimum age. In 1994 the 3 samples tested showed to be about 1800 years old. From these results Brown revised his age estimate to be between 2,000 and 2,200 years old. It is unknown by what criteria he defined the samples’ location in the cross-section or in the vertical column. His conclusion also does not account for that the outer foot of the tree having over a 1,000 years of growth rings.

The naturalist Clarence K. Bennett for whom the tree is named believed the tree to be over 6,000 years old. His conclusion was based upon extrapolations of measurements taken either from core samples or cross-sections of nearby trees. An example is a cross-section from a downed juniper about 200 feet away which was 16” in diameter and 800 years old. About 10 miles away is the Scofield Juniper stump which is about 6 feet in diameter and 2700 years old by ring count. A major issue with the extrapolation method is that the Bennett has some access to water in a drainage which is unusual in this area for junipers. Any extrapolations are tricky at best.

The Site

The Bennett Juniper grows in an open area at an 8400’ elevation just off the top of a ridgeline. The site was heavily glaciated during the last ice age stripping the site of any previous soils. Current soils vary between 6 and 24” thick and are derived from the underlying volcanic bedrock. While sitting in a dry spot, the roots on one side of the tree can reach a seasonal drainage. The area is dominated by low growing (18”) sagebrush (Artemisia tridentata) and scattered lodgepole pine (Pinus contorta murrayana) and a few juniper. Because of fire suppression since the 1950s there is more sagebrush and young trees (both lodgepole and juniper) than would be historically normal for the preserve. Once the sagebrush established its dominance very few young trees have started since 1960. It should be noted that there are a number of junipers within several miles whose height (not other dimensions) rivals the Bennett. In each case they are growing on glacial till or more commonly a glacial moraine with its much deeper soil and water availability.

Human History

The Native Americans certainly visited this area in the summer time, though no specific history regarding the tree is known. Within a half mile of the preserve are 5 locations with bedrock mortars and several spots where obsidian was worked. The earliest known sighting, probably in the 1920s, of the Bennett was by Basque sheepherders who described a huge juniper to their employer, Ed Burgson, a local Tuolumne County sheep rancher. The naturalist Clarence Bennett who had traveled throughout the Sierra studying junipers connected with Burgson a few years later. This was the largest specimen that Bennett had ever seen. Bennett became a champion of getting the tree studied and protected. By the 1950s the Forest Service had named the tree after Bennett.[10] Note that neither the land or the tree was owned by government.

It quickly became apparent after a road was built into the area in the 1950s that the Bennett was going to need some protection from visitors. The first attempt was the formation of the Bennett Juniper Association. Other than a monument being placed in 1963 the group apparently did nothing. Joseph W. Martin (Sr.) the owner of the land on which the Bennett resides and Clarence Bennett were getting on in their years and decided that establishing a formal nature preserve and transferring it to a major established conservation organization was the best method of long term protection for the Bennett. Martin carved out a 3+ acre piece of land from his holdings in the area. It was donated to Nature Conservancy in 1976. As it turned out the Conservancy was not in a position to manage the preserve. Cumulative impact from an increasing number of visitors was taking its toll. John B. Dewitt, the Executive Director of Save-the-Redwood League, had been a regular visitor to the Bennett for many years. He could see how the site was being degraded and foresaw irreversible damage was on the verge of happening. He convinced his Board of Directors that the League should acquire the property and take on the responsibility for the protection of the Bennett. Nature Conservancy transferred title to the League in 1987. The following year the League hired a summer resident steward to manage the visitation and repair previous impacts. The preserve has been staffed since then.