Skip navigation

Weed Identification

smooth pigweed

Family

Amaranthaceae

Scientific Name

Amaranthus hybridus

Other Common Names:

red amaranth
smooth amaranth
slim amaranth

Synonyms (former Scientific Names):

Amaranthus chlorostachys
Amaranthus incurvatus
Amaranthus patulus

Habit

This erect summer annual flowers from June through October.

Leaves

The alternate leaves are oval to egg shaped. The leaves are green on the upper surface and light green to magenta on the lower surface. The stems are densely hairy with short hairs.

Identifying Characteristics

This plant can be distinguished from other pigweeds by it's smaller, less bristly, limp flower spikes.

Flower Seed Head

The small greenish flowers occur in terminal spikes. The male and female flowers occur in different places, the males on the terminal spikes, and the females in smaller spikes of flowers at the leaf axils.

Seed Fruit

The glossy black seeds each form inside a 2 mm long utricle that splits open at maturity.

Where Found

This plant can be found in pastures, along roadsides, and other disturbed soils.

Growth Habit

upright and nonwoody

Thorns or Spines

not present

Dominant Flower Color

Varies: 
purple
green

Leaf Hairs

has hairs

Leaf Shape

Varies: 
round
oval

Leaf Arrangement

alternate

Leaf Margin

Varies: 
entire
wavy

Leaf Structure

simple

Leaf Stalk

shorter than leaf

Stem Hairs

has hairs

Stem Cross Section

round or oval

Milky Sap

not present

Root Structure

taproot

Life Cycle

summer annual

Plant Type

Herb