Invasive Weed Management

Skill 1: Invasive Weed Identification

Contents

Learning Objectives

[2] recognise and name common and high priority invasive weeds of Mendocino County, and obtain assistance from resources in the identification of unfamiliar invasive weeds;

Narrative

Plant identification is the process of determining the name of a particular plant sample. It is more of an art than a science. It is important to know the vegetation species that are present or may be introduced to a site in order to knowledgably manage them.
Plants are called by common names and scientific names. Common names may be applied to more than one species (examples foxtail, iceplant, pampas grass), so identification by common name is not always precise. However, scientific names are currently in a state of flux, with many names being changed to reflect increased understanding of plant evolution derived from molecular analysis of genetic material (DNA, RNA).
Field guides, taxonomic keys and interactive keys are the tools available to assist in identifying an unfamiliar species. The exercises below provide practice in using these tools.
Identification by sight is the method most used by experienced naturalists and weed workers. One should be careful to avoid confusion with species that look similar, especially at certain growth stages. For example, there are native thistles as well as weedy thistles. Both tend to have spiny leaves in their rosette stages, but can be more easily identified at later stages by flower color and shape as well as unique leaf characteristics. Native and invasive Himalayan blackberry have different leaflet structure (3 for native, 5 for invasive) as well as markedly different prickle shape and stem characteristics. Black and white pampas grass can be easily distinguished when blooms are fresh, but the white plumes gray with age. Grasses are notoriously difficult to identify- training, experience and patience are required.
Professional assistance may be required in identifying difficult or unusual species. Samples may be sent to the CDFA's Plant Pest Diagnostic Center for identification, but expect a long turn-around time. A list of professional botanists is available on request from the Mendocino County Planning Department (463-4281) - ask for the Mendocino County Consultant List.

Exercises

  1. After viewing a display of common and alert weed samples and photos, students identify a set of common and alert weed samples or photos provided by the instructor.
  2. Use the interactive keys for grasses or broadleaf weeds to identify samples of uncommon weed samples.
  3. Research a particular weed species in the books and/or online resources listed in the reference section for information to verify an identification. In particular, look for habitat, growth characteristics, blooming season, and lists of species, especially native species, with which it may be confused.
  4. Prepare a sample following the CDFA Plant Pest Diagnostics Laboratory guidelines.

References

 
The content of the page was last modified 2007-09-13