What's Growing On
Fall 2003

by Jason Lopez, Resources and Trails Manager

Weeds vs. Wildflowers

 The effects of the drought that we have been experiencing the past few years became very evident this spring with the return of rain and wildflowers to the Park. Enthusiasm was in the air as old friends such as Canchalagua and Indian paintbrush decided to visit for a while. Certain locations with enough shade and moisture sustained wildflowers into the summer months. Park trails provide great access for viewing because the edge of the trail tread is often lined with native flowers. Walking along a meandering trail with flower pedals brushing against your leg was probably not your experience this spring because also with the rain and wildflowers came the weeds.  

Unfortunately, our open space and trails are inundated with non-native pests such as the prickly Tecolote star thistle and voraciously growing black mustard. Weeds grow intermixed with native species.

This presented a dilemma for Park field staff because the weeds along trails need to be trimmed back to ensure that trail users will stay on the designated trails, out of wildlife habitat and can safely use the trail. But it is also important that the wildflowers have an opportunity to produce seed for the next wet winter. Wildflowers grow well along the trail because there is often less competition with weeds due to maintenance and recreational usage. The timing and technique of the trail trimming is important. Trails can be trimmed to avoid wildflowers, but the people doing the work need to have a trained eye and be able to determine what is a weed and what is a wildflower. With limited staff this can be challenging because the Park maintains about 22 miles of designated trail, regrettably not all lined with wildflowers.

Various terms define a plant that does not belong. Exotic, invasive, non-indigenous, pest, non-native and noxious all have a specific meaning that best describes a type of plant in a certain situation. The term weed is a common and general term, and, according to the book Invasive Plants of California Wildlands, weeds can be defined as “species, population, and individual plant that are unwanted because they interfere with management goals.” Since a primary management goal of the River Park is to preserve and restore land, deciding what is a weed is essential. Along an overgrown trail, weeds may direct people off the trail or may discourage usage. It is important for people not to be discouraged while visiting natural areas so that they appreciate the atmosphere and support further preservation.

Off the trail in wildlife habitat, weeds present huge problems. Along with the blooming natives this spring weeds demonstrated their dominance at Lake Hodges and San Pasqual Valley. In many areas where previous disturbances such as grazing, farming, grading, etc. have occurred, the weed coverage far exceeds that of the native plants. Considering the amount of historic land use in the area, one can imagine the amount of acreage that is covered by weeds.

Once established, weeds have a tremendous capacity to invade natural plant communities and prohibit native plant recovery. Typically, they steal precious moisture, nutrients and sunlight from native plants that provide wildlife a food source, nesting area and water. While visiting a park, look around at the composition of the vegetation and be aware of the weed issue. It is very possible that weeds pose the greatest threat to biodiversity on land that is already preserved.