Forest Nursery Notes, Summer 2007. Altland, J. Oregon Association of Nurseries monthly publication Digger 51 (3):32
The most straightforward and simple approach to weed identification is the use of a program by XID Services Inc. (www.xidservices.com/). Along with Dr. Richard Old, XID Services developed a computer program that allows the user to identify weeds and other plants by simply inputting one or more plant characteristics. The program is a user-friendly database that contains thorough details of 600 to 3,000 weed species (depending on the version you purchase).
The XID software allows the user to input any number of plant physical characteristics, which in turn narrows the list of possible plant matches. For example, telling the computer that the weed in question has pink flowers narrows the list of possibilities from 512 to just 127 species. Further adding that the flowers of the weed in question contain two sepals, narrows the list to just seven species. Photos and descriptions of the remaining seven possibilities are provided. A quick survey of the possibilities reveals the name of the weed in question.
A vast array of plant characteristics pertaining to its flowers, stems, leaves, and roots can be entered into the computer to narrow the possible list of weeds into a manageable list. I input only those characteristics of which I am certain. Counting the number of petals or sepals, describing flower color or describing the pubescence on the foliage are very discrete plant characteristics that allow me to narrow a list of potential species from several hundred to just 10 or less. From that list the software provides digital images of the species to that a potential match can be made. Using Internet searches for additional photos, I further verify the identity of the weed in question. I used this approach to identify many weed species in the Willamette Valley.
It’s best to avoid using variable or objective plant characteristics. For example, plant size is a poor characteristic to use, considering that the weed in question may have been mowed, grazed or otherwise adversely affected by the environment. Characteristics such as leaf size and even leaf shape can vary, depending on climate and growing conditions. These are often variable, and ultimately less useful, characteristics and should be avoided when identifying plants.
This software can be purchased containing a number of different plant databases. One database contains 1,000 weeds throughout America. Identical software can be purchased containing a database of the flora of Oregon or the Pacific Northwest (3,076) species). I prefer to use the database of Northwest weeds that describes 600 species in our region of the U.S. The www.Flora-ID-Northwest.com website offers databases for many different states and regions of the U.S. and Canada.