How to Identify Lawn Weeds in Arizona

Identifying lawn weeds in Arizona.

According to the University of Arizona, a weed is any plant that grows where it's unwanted or is unwelcome because of its undesirable characteristics. Three main categories of common weeds annoy gardeners: sedge, grass weeds and broadleaf weeds. In addition, weeds may be further subdivided into cool and warm season plants, and according to their life cycles as well: annual, biennial and perennial. The presence of many weeds may be the result of improper gardening and lawn care. An unhealthy lawn is left wide open to weeds. Gardeners must keep an eye on their lawn throughout the year, especially in Arizona where winters are mild.

Things You'll Need

• Soil pH test

Instructions

1. Examine your yard for growing weeds. Broadleaf weed flowers are generally more colorful than grasses and sedges. Sedges resemble grass weeds, but their stems usually have a triangular shape rather than the flat or round stems seen in grass weeds. Also, grasses have a prominent mid-vein.

2. Look in areas around the yard, such as in ditches and along the road. Weeds growing near these run-off areas tend to be very aggressive and commonly include puncturevine, common sunflower, Russian thistle and spiny aster.

3. Note the time of year. Summer-growing weeds include red sprangletop, Palmer amaranth and crabgrass. Winter weeds include London rocket, nettleleaf, spiny sowthistle and silversheath knotweed.

4. Dig up the weed in question and inspect its root system. Annual weeds have a shallow root system, whereas perennial weed roots are usually deep and extensive. Annual weeds include yellow sweetclover, little mallow and camphorweed. Dandelion, broadleaf plantain and dallisgrass are examples of perennial weeds.

5. Check the pH range of various weeds. This is a scale that measures how acidic or alkaline soil is. Purchase a soil pH test from your local gardening supply store, and follow the directions to test your soil. Each plant has a range of pH it prefers to grow in, so you can narrow down the list of weeds likely to be growing in your soil. For instance, dandelions need a soil pH range of 4.8 to 7.5.

Tips & Warnings

• Contact your local cooperative extension office for a list of Arizona weeds common in your area.

• Avoid using a broad-spectrum herbicide on lawns, because it will kill the surrounding grass areas.

References

• The University of Arizona: Arizona Weeds
• University of Texas: Choosing the Right Herbicide for Weed Control
• The University of Arizona: Arizona Cooperative Extension: Non-native, Invasive Plants of Arizona