California Pest Control Adviser PCA Weeds: Weed ID Exam
Guide 2026|: Weed Identification and Management|2026
Full-Length Practice Examination.
Section 1: Weed Identification (Morphology & Taxonomy)
1. You are called to a ranch in the Central Valley to advise on a late-winter weed. The
seedling has a rosette of hairy leaves, and upon close inspection, the stem is square.
Which of the following is most likely the genus?
A) Amaranthus
B) Senecio
C) Lamium
D) Chenopodium
Answer: C) Lamium
Rationale: Lamium (Henbit/Deadnettle) is in the Lamiaceae (mint) family, characterized by
square stems and opposite leaves. Amaranthus (pigweed) has thick, fleshy
stems; Senecio (groundsel) has a round, often fleshy stem; Chenopodium (lambsquarters)
has a round, often striated stem.
2. A grower brings in a grass seedling that has a membranous structure covered in small
hairs at the junction of the leaf blade and sheath. What is this structure called, and why is
it important?
A) Auricle; it clasps around the stem to prevent water loss.
B) Ligule; it is a key diagnostic feature for identifying grass species.
C) Collar; it is the site of meristematic growth.
D) Sheath; it wraps the stem to provide structural support.
Answer: B) Ligule
Rationale: The ligule is the membranous or hairy appendage on the inside of the leaf at the
junction of the blade and sheath. Its presence, absence, or type (membranous vs. hairy) is
critical for distinguishing between grass species at the seedling stage.
3. Which of the following weeds is a perennial that spreads primarily via rhizomes and is
notoriously difficult to control in row crops?
A) Avena fatua (Wild oat)
B) Convolvulus arvensis (Field bindweed)
,C) Capsella bursa-pastoris (Shepherd’s-purse)
D) Salsola tragus (Russian thistle)
Answer: B) Convolvulus arvensis
Rationale: Field bindweed is a deep-rooted perennial that spreads by both seeds and
extensive creeping roots (rhizomes). Wild oat and Shepherd’s-purse are annuals; Russian
thistle is an annual tumbleweed.
4. A seedling emerges in the spring with large, fleshy, cotyledons and later develops a
hairy stem and large leaves. It is toxic to livestock and has a foul odor. What weed is this?
A) Datura stramonium (Jimsonweed)
B) Abutilon theophrasti (Velvetleaf)
C) Portulaca oleracea (Purslane)
D) Tribulus terrestris (Puncturevine)
Answer: A) Datura stramonium
Rationale: Jimsonweed is a summer annual in the Solanaceae family. It is characterized by
large, coarsely toothed leaves, a foul odor, and spiny seed pods. All parts are highly toxic to
animals and humans.
5. You find a low-growing, prostrate weed with small, opposite leaves that exudes a milky
sap (latex) when the stem is broken. Which weed fits this description?
A) Euphorbia maculata (Spotted spurge)
B) Malva parviflora (Cheeseweed)
C) Polygonum aviculare (Prostrate knotweed)
D) Stellaria media (Common chickweed)
Answer: A) Euphorbia maculata
Rationale: Spotted spurge is identified by its prostrate growth, dark spot on the leaves, and
the distinct milky latex sap (a hallmark of the Euphorbiaceae family).
6. Which structural feature is found ONLY in grasses and is used extensively for
identification?
A) Hypocotyl
B) Cotyledon
C) Ligule
D) Petiole
Answer: C) Ligule
Rationale: The ligule is a membrane or fringe of hairs found on the inner side of the grass
leaf at the junction of the blade and sheath. Dicots (broadleaves) do not possess this
structure.
7. A perennial grass weed is identified by its large, creeping rhizomes, thick stems, and a
dark purple-brown panicle. This is likely:
, A) Lolium multiflorum (Italian ryegrass)
B) Sorghum halepense (Johnsongrass)
C) Poa annua (Annual bluegrass)
D) Echinochloa crus-galli (Barnyardgrass)
Answer: B) Sorghum halepense
Rationale: Johnsongrass is a tall, perennial grass that spreads aggressively via rhizomes. Its
seed head is a loose, purplish panicle. It is one of the most troublesome perennial grasses in
California agriculture.
8. A grower in a tomato field shows you a vine with large, showy white flowers and heart-
shaped leaves. You explain this is a morningglory species. What scientific genus does this
belong to?
A) Solanum
B) Convolvulus
C) Ipomoea
D) Physalis
Answer: C) Ipomoea
Rationale: While field bindweed (Convolvulus arvensis) is a vine, the large, showy
morningglories common in agronomic fields generally belong to the
genus Ipomoea. Solanum is nightshade; Physalis is groundcherry.
9. A seedling has a rosette of deeply lobed, prickly leaves with a white mid-vein. If left to
mature, it will produce a dandelion-like puffball of seeds. What is the common name?
A) Common groundsel
B) Prickly lettuce
C) Annual sowthistle
D) Shepherd’s purse
Answer: B) Prickly lettuce
Rationale: Lactuca serriola is characterized by the prickly hairs on the underside of the leaf
mid-vein and the rosette growth habit. It is a winter annual.
10. A weed sample has triangular stems and produces "nuts" (tubers) at the tips of
rhizomes. What is the correct classification of this plant?
A) Grass (Poaceae)
B) Broadleaf (Dicot)
C) Sedge (Cyperaceae)
D) Rush (Juncaceae)
Answer: C) Sedge (Cyperaceae)
Rationale: Sedges (like Cyperus species) are characterized by solid, triangular stems and
Guide 2026|: Weed Identification and Management|2026
Full-Length Practice Examination.
Section 1: Weed Identification (Morphology & Taxonomy)
1. You are called to a ranch in the Central Valley to advise on a late-winter weed. The
seedling has a rosette of hairy leaves, and upon close inspection, the stem is square.
Which of the following is most likely the genus?
A) Amaranthus
B) Senecio
C) Lamium
D) Chenopodium
Answer: C) Lamium
Rationale: Lamium (Henbit/Deadnettle) is in the Lamiaceae (mint) family, characterized by
square stems and opposite leaves. Amaranthus (pigweed) has thick, fleshy
stems; Senecio (groundsel) has a round, often fleshy stem; Chenopodium (lambsquarters)
has a round, often striated stem.
2. A grower brings in a grass seedling that has a membranous structure covered in small
hairs at the junction of the leaf blade and sheath. What is this structure called, and why is
it important?
A) Auricle; it clasps around the stem to prevent water loss.
B) Ligule; it is a key diagnostic feature for identifying grass species.
C) Collar; it is the site of meristematic growth.
D) Sheath; it wraps the stem to provide structural support.
Answer: B) Ligule
Rationale: The ligule is the membranous or hairy appendage on the inside of the leaf at the
junction of the blade and sheath. Its presence, absence, or type (membranous vs. hairy) is
critical for distinguishing between grass species at the seedling stage.
3. Which of the following weeds is a perennial that spreads primarily via rhizomes and is
notoriously difficult to control in row crops?
A) Avena fatua (Wild oat)
B) Convolvulus arvensis (Field bindweed)
,C) Capsella bursa-pastoris (Shepherd’s-purse)
D) Salsola tragus (Russian thistle)
Answer: B) Convolvulus arvensis
Rationale: Field bindweed is a deep-rooted perennial that spreads by both seeds and
extensive creeping roots (rhizomes). Wild oat and Shepherd’s-purse are annuals; Russian
thistle is an annual tumbleweed.
4. A seedling emerges in the spring with large, fleshy, cotyledons and later develops a
hairy stem and large leaves. It is toxic to livestock and has a foul odor. What weed is this?
A) Datura stramonium (Jimsonweed)
B) Abutilon theophrasti (Velvetleaf)
C) Portulaca oleracea (Purslane)
D) Tribulus terrestris (Puncturevine)
Answer: A) Datura stramonium
Rationale: Jimsonweed is a summer annual in the Solanaceae family. It is characterized by
large, coarsely toothed leaves, a foul odor, and spiny seed pods. All parts are highly toxic to
animals and humans.
5. You find a low-growing, prostrate weed with small, opposite leaves that exudes a milky
sap (latex) when the stem is broken. Which weed fits this description?
A) Euphorbia maculata (Spotted spurge)
B) Malva parviflora (Cheeseweed)
C) Polygonum aviculare (Prostrate knotweed)
D) Stellaria media (Common chickweed)
Answer: A) Euphorbia maculata
Rationale: Spotted spurge is identified by its prostrate growth, dark spot on the leaves, and
the distinct milky latex sap (a hallmark of the Euphorbiaceae family).
6. Which structural feature is found ONLY in grasses and is used extensively for
identification?
A) Hypocotyl
B) Cotyledon
C) Ligule
D) Petiole
Answer: C) Ligule
Rationale: The ligule is a membrane or fringe of hairs found on the inner side of the grass
leaf at the junction of the blade and sheath. Dicots (broadleaves) do not possess this
structure.
7. A perennial grass weed is identified by its large, creeping rhizomes, thick stems, and a
dark purple-brown panicle. This is likely:
, A) Lolium multiflorum (Italian ryegrass)
B) Sorghum halepense (Johnsongrass)
C) Poa annua (Annual bluegrass)
D) Echinochloa crus-galli (Barnyardgrass)
Answer: B) Sorghum halepense
Rationale: Johnsongrass is a tall, perennial grass that spreads aggressively via rhizomes. Its
seed head is a loose, purplish panicle. It is one of the most troublesome perennial grasses in
California agriculture.
8. A grower in a tomato field shows you a vine with large, showy white flowers and heart-
shaped leaves. You explain this is a morningglory species. What scientific genus does this
belong to?
A) Solanum
B) Convolvulus
C) Ipomoea
D) Physalis
Answer: C) Ipomoea
Rationale: While field bindweed (Convolvulus arvensis) is a vine, the large, showy
morningglories common in agronomic fields generally belong to the
genus Ipomoea. Solanum is nightshade; Physalis is groundcherry.
9. A seedling has a rosette of deeply lobed, prickly leaves with a white mid-vein. If left to
mature, it will produce a dandelion-like puffball of seeds. What is the common name?
A) Common groundsel
B) Prickly lettuce
C) Annual sowthistle
D) Shepherd’s purse
Answer: B) Prickly lettuce
Rationale: Lactuca serriola is characterized by the prickly hairs on the underside of the leaf
mid-vein and the rosette growth habit. It is a winter annual.
10. A weed sample has triangular stems and produces "nuts" (tubers) at the tips of
rhizomes. What is the correct classification of this plant?
A) Grass (Poaceae)
B) Broadleaf (Dicot)
C) Sedge (Cyperaceae)
D) Rush (Juncaceae)
Answer: C) Sedge (Cyperaceae)
Rationale: Sedges (like Cyperus species) are characterized by solid, triangular stems and
