Thanks to the contributions of two energetic people who know plants, chavezpark.org is publishing a complete botanical inventory of the park. Jutta Burger PhD is Lead Scientist for the California Invasive Plant Council, and Bob Huttar is a certified arborist and a consulting field biologist specializing in botany generally and rare plants in particular. Together they are photographing and identifying everything that grows in the park, both common and scientific names. They’ve done the scientific heavy lifting. I’m adding some background blog-talk. We’re going to publish the results in a series, with a new installment every Friday.
This week’s featured park plants are four grasses: Kikuyu Grass, Orchard Grass, Upright Veldt Grass, and the Slender Wild Oat.
(1) Kikuyu Grass
The Kikuyu Grass occupies a lot of territory in the park, and thereby hangs a story. As many readers of this blog will know, Cesar Chavez Park is an entirely man-made area, an unalloyed example of the Anthropocene. About 1.6 million tons of garbage lie under the surface, covered by a motley mixture of clay, construction dirt (including excavation of the BART tunnel), and soil of unknown origin. Early gardeners likened the soil to “mine spoils.” The initial effort to green it up in the 1980s was done by hydroseeding (spraying from a truck) a mix of Alta Tall Fescue, Derby Perennial Rye, and Dutch White Clover. After several efforts, this was reported in early 1988 as successful, “except for the presence of kikuyu grass.” This grass, predicted the environmental consultant, “will eventually take over the turf if left unchecked.” It is extremely difficult to remove , said the consultant. Repeated applications of a systemic herbicide (glyphosate) would be effective if applied while the Kikuyu grass is still young. Once it is established, herbicide is futile.
“The resultant kikuyu lawn will form a deep thatch layer resulting in a thick springy turf. The surface is generally unsuitable for sports and field games, affecting both footing and ball movement, but it is drought tolerant, extremely hardy, and suitable as an informal, unstructured recreation surface.”Malcolm J. Sproul, Principal of LSA Associates Inc., letter to John Roberts, John Northmore Roberts & Associuates, February 18, 1988.
A January 1990 report on park vegatation authored by Nikki Wright and Jazz Duberman, then the members of the Park gardening staff, traced the origin of the Kikuyu grass to the installation of the landfill gas collection system in 1988, which disturbed the soil throughout the park for the installation of 12,000 feet of PVC pipe in trenches. They wrote:
Kikuyu grass, an extremely invasive rhizomatous weed, and many broad-leafed weeds, have become rooted and are propagating very noticeably in the Lower Meadow since that disturbance occurred.”
Wikipedia observes that many golf courses use this grass in the rough, and it is popular as a residential lawn in Southern California. It’s inexpensive, drought-tolerant, and grows fast. On the other hand, once you have it, it’s a problem to control it.
It has high invasive potential due to its elongate rhizomes and stolons, with which it penetrates the ground, rapidly forming dense mats, and suppressing other plant species. It grows from a thick network of rhizomatous roots and sends out stolons which extend along the ground.
It can climb over other plant life, shading it out and producing herbicidal toxins that kill competing plants. It prevents new sprouts of other species from growing, may kill small trees and can choke ponds and waterways. It is resistant to mowing and grazing due to its strong network of roots, which easily send up new shoots. It springs up in turfs and lawns, and can damage buildings by growing in the gaps between stones and tiles. The plant is easily introduced to new areas on plowing and digging machinery, which may transfer bits of the rhizome in soil clumps. While the grass spreads well via vegetative reproduction from pieces of rhizome, it is also dispersed via seed. Rhizomes that have reached very hard to reach places will continue to grow as separate plants if they are snapped off during the attempted removal process.
(2) Orchard Grass
Orchard Grass, according to the California Invasive Plant Council (CalIPC) is an aggressive invader that grows in any type of soil, is drought resistant, and is capable of overrunning other grasslands. Wikipedia says that it’s a perennial native to Eurasia or North Africa, it’s a kind of bluegrass, and some call it cocksfoot grass. It’s also known as cat grass because domestic cats like to chew it. Many butterfly caterpillars also like to feed on it. More about it on CalPhoto and CalFlora.
(3) Upright Veldt Grass
Ehrharta erecta or Upright Veldt Grass is also known as Panic Veldt Grass, possibly because its arrival is cause for alarm. Native to Southern Africa and Yemen, it’s “a documented invasive species in the United States” and elsewhere, according to Wikipedia. It’ll grow almost anywhere, with or without sun. It flowers and seeds year round. Its seeds germinate rapidly, forming new plants in just a few weeks. This means that mowing in an effort to stop it is most likely to help it spread by broadcasting its seeds. See CalPhotos and CalFlora.
(4) Slender Wild Oat
Avena barbata, at least the variety we have in California, is a gift of the Spanish conquistadores who ravaged the Americas in the 16th and 17th centuries. So says Wikipedia, citing genetic evidence; this grass has been the focus of intensive genetic studies. In North America generally and California especially, according to the same source, “it is an introduced species and noxious weed … it has displaced native species of grass.” It does well in sandy/poor soils; ranchers introduced it for forage, and it replaced native perennial grasses. To its credit, its seeds are edible. Check it out on CalPhotos, CalFlora and CalIPC.