Weeds In Bidwell Park
John Dittes, July 2003
What Is A Weed? A tomato farmer may tell you it's anything that's not a
tomato; a forester may tell you a weed is anything but a tree! Biologists will
give you a different definition yet. From an ecological perspective, weeds are
organisms (plants or animals) that share a set of traits that allow invasion,
persistence, and domination over pre-existing biological communities,
particularly where human activities occur.
Weeds are usually non-native, although a few native species behave like
weeds. California Poppy, our State Flower, is a noxious weed in Chile! Other
weedy natives include Fiddleneck, Doveweed, Cocklebur, Coyote Bush and
even White Fir.
Weeds Usually Share The Following Traits:
- Weeds are prolific, reproducing with abundant seeds (Tamarisk), by
vegetative cloning with rhizomes (underground stems as with Periwinkle), or
with stolons (aboveground stems as with English Ivy),
- Weeds are easily dispersed by wind (Dandelions, Tree of Heaven), by
mammals (Foxtail Grass and Cocklebur), by birds (Privet, Edible Fig, Olive and
Himalayan Blackberry), by water (Giant Reed and Purple Loosestrife), and by
people (Puncture Vine in bicycle tires),
- Weed seeds usually are long lived in the "soil seed bank",
- Weeds can germinate and grow under a wide variety of environmental
- Weeds out-compete other species with "strategies" that include rapid
lateral, or "overtopping" growth, and the physiological ability to thrive under
conditions that are poor for other species.
Why We Should Care About Weeds in Bidwell Park: Bidwell Park harbors a
wealth of biological diversity unparalleled by any other Municipal Park in
California. Over 750 species of vascular plants, 60 species of mosses, 131
species of birds, 55 mammals, 15 reptiles, 9 amphibians and 11 different
species of fish have been observed. Thousands of insect species have yet to be
- Weeds out-compete other native plant species, resulting in reduced
biodiversity and "simplified and vulnerable ecosystems",
- Weeds usually fail to provide requirements for diverse native wildlife
- Weed-dominated plant communities are generally not as aesthetically
pleasing as more intact native ones,
- Weed-dominated plant communities often present increased fire danger.
Bidwell Park's Invasive Weeds:
In Lower Park: The herb and shrub layer under the majestic native oaks and
sycamores along the riparian corridor is dominated almost entirely by
aggressive non-native species including Periwinkle, Privet, English-Ivy and
Himalayan Blackberry. Giant Reed Grass and Tree of Heaven are scattered
along the creek edges as well. Other species that are more recently spreading
in Lower Park include Bladder Senna, Pyracantha (Firethorn) and Perennial
Pepperweed. Although Pampas Grass is located in nearby gardens, it has yet to
dominate sites in the park.
Spanish broom near Diversion Dam
In Upper Park: Yellow Star Thistle and Medusa-Head Grass dominate many
grassland areas. Olives are spreading and already dominate areas on the south
side of the creek. Edible Fig, Spanish and French Broom, and Giant Reed Grass
are spreading at scattered sites along the floodplain of Big Chico Creek.
Although many of these plants are attractive and can even provide food and
shelter for select wildlife species, they are quickly replacing large numbers of
native plant species and the astonishing diversity of animal species depending
on them. Upper Park stands to lose a unique component of California's natural
heritage, one that was appreciatively described over 100 years ago by the
Ironically, the Bidwells were enthusiastic about farming and gardening and
actually introduced some of the "weeds" that are now threatening the Park.
Ivy-choked trees in Lower Park
What Can You Do?
- Participate in Bidwell Park "Weed Bashing Projects"- These efforts are
led by organizations including the California Native Plant Society,
Streaminders, Kids and Creeks, Friends of Bidwell Park, and the amazingly
energetic Laura Nissim. You can contribute muscle and sweat, or financial
- Stay On Existing Trails- We spread weeds when we pass through weedy
areas along trails and then into native undisturbed areas. We collect and
spread weed seeds with socks, shoelaces, pants, dogs, horses and bicycles. By
traveling off of existing trails, we create new disturbed surfaces that foster
- Landscape Responsibly- Avoid landscaping with any of the above-
mentioned species. When visiting local nurseries, express your concerns to the
Nursery Managers when you see any of these invasive species offered for sale.
Tell your friends, as they may unknowingly be planting or caring for invasive
species. Also, landscape with native species; they tend to be drought tolerant
and more attractive to native birds and insects.
- Promote Responsible Park Stewardship- By participating with the City of
Chico in the development of a comprehensive Bidwell Park Master