know your weeds

some common weed varieties in the southwest


The term “weed” means different things to different people.  In the broadest sense, it is any plant growing where it is not wanted. Weeds can be native or non-native, invasive or non invasive, and noxious or not noxious.

From a grass that is causing the destruction of saguaros to a flower that can poison you if you touch it to a seed that hurts more to step on than a Lego brick, learn why some plants have been classified as “noxious.

Grass Kids 1


  • Stinknet can cause severe breathing problems and severe skin reactions when handled. The name “stinknet” comes from the strong odor that sometimes comes from the plant, especially when some of the leaves are crushed.
  • Starting in February and continuing through May, the plant has bright yellow, round flowers that have no petals. These ball-shaped blooms may look fun, but the issues they cause are not worth keeping these dangerous plants around.
  • Mature plants may grow up to almost 10 feet tall but in general are found growing to about 3 ft.
  • Under certain conditions, free nitrates in redroot pigweed leaves are high enough to be toxic to livestock when consumed.
Grass Kids 1


  • Bufflegrass was first introduced in the U.S. in the 1920s and 30s as a form of erosion control. Here in the Sonoran desert, however, it quickly took over many of our native plants. It uses up water, nutrients, and sunlight that other plants (including saguaros) desperately need.
  • Once it grows into a thick clump, each clump can produce THOUSANDS of seeds.

  • Once the temperatures rise, buffelgrass goes dormant and becomes brown, dry, and brittle.  The wildfires that have ripped through Arizona – easily spread because of the buffelgrass – destroy native species that take years and years to regrow.

Grass Kids 2

Puncturevine aka “Goat Head”

  • Goat Head is a small plant with yellow flowers. The plant, however, isn’t the nuisance – the seeds are. They can injure pet paws, be painful to step on, and have caused endless bike tire flats.
  • The spiny seedpods often lie hidden under the plant. Mature seedpods break apart into 5 burs, each containing 2–4 seeds, which are viable for up to 7 years.
  • It can flower throughout the spring, summer, or fall, and the flowers are followed by fruit with spines. The seeds slightly resemble a goat head (hence its most well-known name). The plant itself is considered a noxious weed in Arizona.
Grass Kids 1


  • It has wide leaf blades, much like the turf grass in which it may grow.
  • The base of the leaves has fine hairs and the stem rises from a collar at the base of the leaf. Stems bear 3 – 10 inch long spikes of flowers, which yield to seeds at the end of the season.
  • When the needle-like seed heads on foxtails grasp onto an animal’s fur, they can burrow inside their nose, mouth, paws, eyes and/or tails. This is particularly true of longhaired dog and cat breeds. Once they become ingested or embedded in your pet, the hooking design that allows them to drill into soil to germinate will also keep them plowing forward inside your pet. This can cause pain, infection, perforated lungs, abscesses, and even death.
Grass Kids 1

Prickly Lettuce

  • Leaves are oblong football shaped to egg shaped, often have slightly indented tips, have bases that abruptly taper into a short stalk, and usually have a few fine, gland-tipped hairs, especially on the edges.
  • The mature plant can grow up to 6.5 feet tall.
Grass Kids 1

Russian Thistle

  • Russian thistle is a large and bushy noxious annual broadleaf plant.
  • Mature plants are large and bushy with rigid, purple-streaked or green stems that typically curve upward giving the plant an overall round shape.
Grass Kids 2

London Rocket

  • Plants exist as rosettes until they develop flowering stems at maturity.
  • Stems mostly branch near the base, and usually grow to about 2 feet tall. Leaves are nearly hairless.
Synthetic Grass Dog

Silverleaf Nightshade

  • A member of the tomato family, silverleaf nightshade is a branched and deep rooted perennial herb that grows 1 to 4 feet in height with purplish-blue flowers.
  • Silverleaf nightshade lowers crop yield through competition. The species is also toxic to livestock.
Grass Kids 1


  • Filaree plants are low-growing, common winter annual and sometimes biennial broadleaves.
  • Depending on the species, stems grow from spreading to more-or-less erect and reach 2 to 3 feet in height or length.
Grass Kids 1

Redroot Pigweed

  • Leaves are oblong football shaped to egg shaped, often have slightly indented tips, have bases that abruptly taper into a short stalk, and usually have a few fine, gland-tipped hairs, especially on the edges.
  • The mature plant can grow up to 6.5 feet tall.
Synthetic Grass Dog


  • It has square stems covered with white hairs with leaves opposite each other. Leaves are hairy above, with a crinkled surface, and are sharply aromatic when crushed.
  • It has small white flowers above the nodes (where the leaves join the stem) around the upper sections of the stems.
  • Clusters of flowers dry to form brown burrs with small hooked spines. Each burr contains up to 4 small spear-shaped seeds.

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