Pistachio

Barnyardgrass

(Echinochloa crus-galli) Grass family; first leaf dull gray green; stem flattened, purplish; no ligule.

Common knotweed

(Polygonum arenastrum): Knotweed family; annual or short-lived perennial, germinates during fall or spring; seed leaves are long, very narrow, rounded at the tip and light green with a white cast; true leaves are much broader, emerging from an encircling, membranous sheath at the leaf base.

Common lambsquarters

(Chenopodium album): Goosefoot family; seed leaves are narrow, with nearly parallel sides; seed leaves and early true leaves dull blue green above and often purple below; young leaves have mealy appearance from coating of fine translucent granules.

Common purslane

(Portulaca oleracea): Purslane family; seed leaves oblong, somewhat club-shaped, succulent, maroon on lower surface, and green or maroon on upper surface; young leaves smooth, succulent, oblong, green on upper surface, maroonish underneath, and broadest around leaf tip, with short petioles.

Junglerice

(Echinochloa colona): Grass family; grayish, dull green first leaves; several purple bands on surface of leaf blade; no ligule, no auricle.

Hairy fleabane

(Conyza bonariensis): Sunflower family; annual or biennial; seed leaves gray green; first leaves narrow and covered with short, soft hairs; often wrinkled or distorted.

Horseweed

(Conyza canadensis): Sunflower family; annual or biennial; seed leaves dull green, oval with fine hairs, and with short stalks that sometimes may be tinged brown-purple; first true leaves covered with hairs on upper surface and margins; undersides of early leaves smooth.

Pigweeds

(Amaranthus spp.) Pigweed family; seed leaves narrow.

Puncturevine

(Tribulus terrestris): Caltrop family; seed leaves thick, brittle, 2 to 3 times longer than wide; petioles pinkish; true leaves dark green with grayish underside and rough margins.

Russian thistle

(Salsola tragus): Goosefoot family; cotyledons and first true leaves  long and thin; first leaves are fleshy, soft, and weakly spine-tipped; stems slender and flexible, often with reddish purple striations along their length.