For those interested in seeing a partial view of a full-grown Joshua trees (Yucca brevifolia) root system, read this post. This plant grows along Alamo Road about 5 miles northwest of my property. It predates the road by at least 100 years or so, but just happened to be on the edge of the easement when Alamo Road was widened to its current alignment. Ive noticed this large and beautifully-shaped 15 foot (5 meter) tall tree for years as I drive past it. Although the basally flared trunk was clipped a few times by the county road grader, its mostly been unbothered by the road maintenance activities - until now that is. Heavy late summer rains and flooding about 6 weeks ago have eroded quite a bit of the embankment back toward the trees root system, undermining and exposing it to the sun and the air. As monocot plants, Joshua trees have a fibrous root system like palms and grasses do, as opposed to the woody, branching one of dicot trees. The tangled mat of pencil-thick roots extends laterally about as wide as the trees crown does - about 6 to 8 feet radially in all directions and 3 to 4 feet deep. I placed my shadow into the second image to show a bit of scale for the size. This is a good illustration of how roots do not necessarily need to be huge in order to effectively anchor a large plant to the ground. Thousands of small roots are about as useful as fewer, thicker roots are. Plus the fibrous root systems of yuccas and other monocots are not as prone to heaving sidewalks, cracking foundations, or breaking water or sewer lines as the thick, massive underground roots of large trees like pines, oaks, maples, or eucalyptus, for example. With dicot trees like those, the roots start small and over time can massively increase in diameter, buckling nearby buried or surface objects. Joshua tree roots, while dense, never get thicker in diameter than about 1/4 inch (6 mm), and as such they tend to leave those things intact. The future of this Joshua tree is uncertain. Continued erosion will eventually topple it, and its also in danger from the activities of the road grader and repair work. I hope that it will continue to live, but it may be destroyed by either one of these forces before too long. Therefore, if nothing else, I wish to use the trees plight to help educate people before it disappears. Wish the tree luck!
Posted on: Mon, 21 Oct 2013 07:09:09 +0000
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