When it comes to noxious weeds, few can compare with Pennisetum clandestinum, commonly known as Kikuyu Grass. Its origin is the highland region of central Kenya, home of the Kikuyu people. It has since been introduced to every temperate continent, with the first recorded arrival in California in 1925. It has its good points: cattle fodder, soil stabilization, cheap lawn, golf course roughs. But it takes high maintenance to keep it in check. Once it escapes, it’s a monster. It spreads rapidly both underground via rhizomes, like some bamboo, and at the same time aboveground via tough, thick runners. It can also spread via seeds that can remain viable in soil as deep as six cm for at least ten years, and survive digestion by cattle to sprout in their dung. The rhizomes may run as deep as 2.5 meters (8.2 feet) in some conditions, and a small fragment is enough to regrow the plant and restart its spread. Grazing, mowing, frost, drought, and fire may slow it down but not stop it.
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.https://en.wikipedia.org/wiki/Pennisetum_clandestinum
This weed is on the California Invasive Plant Council list, on the noxious weed list of 45 other states, and on the US federal noxious weed index. In Cesar Chavez Park, it owes its introduction primarily to the controversial establishment of the landfill gas collection system in the late 1980s. More than 40 collection wells and some 16,000 feet of trenches had to be dug to feed the flare station near the center of the park. Two City of Berkeley gardeners, Nikki Wright and Jazz Duberman, submitted a report in January 1990:
When the Park is disturbed, such as occurred when the methane extraction system was installed during the summer of 1988, established areas of the Park were disrupted, primarily the Lower Meadow (established in 1982 with native grasses), and the 2nd Tier along the north-south first pathway. Kikuyu grass, an extremely invasive rhizomatous weed, and many broad-leaf weeds, have become rooted and are propagating very noticeably in the Lower Meadow since that disturbance occurred.https://chavezpark.org/wp-content/uploads/2020/06/1990-02-05-Landscape-report.pdf
There is nothing that can be done at this late date about the Kikuyu in the grassland areas of the park. But in the Native Plant Area — the forested grove on the west side of the park — the danger from Kikuyu Grass to the native shrubs and trees is clear and present, and remedial action is possible, if there are stewards with the vision and the courage to attack it.
Just such stewards are Bob Huttar and Jutta Burger. Regular readers of this blog know them well already: they are the brains, eyes, and legs behind the wonderful Flora Friday series that ran for most of 2019. Bob is an ecologist with an active consulting practice in biological and botanical site surveys. Jutta is an all-around naturalist and senior scientist with the California Invasive Plant Council, and is a member of the Board of Directors of the Chavez Park Conservancy, and its Secretary. They have identified and photographed well over 150 species of plants in this park, all listed here. In past decades, the City has paid consultants hefty sums to generate botanical inventories of this sort. Jutta and Bob have exceeded the quantity and production quality of those efforts entirely as volunteers, out of love for this park. In the face of that kind of scientific sharpness and passionate energy, the Kikuyu Grass ought to tremble. Its kingdom in the Native Plant Area is in deep trouble.
Bob and Jutta had only a few hours to spend on this occasion. Nevertheless, they managed to save significant stands of native Ceanothus, Bishop Pine, and Baccharis from suffocation by Kikuyu. They will be back and they invite other park volunteers to join in the effort. Bob will act as Volunteer Coordinator. If you would like to join this effort, please use the Contact Form at the bottom of this linked page.