roughfruit amaranth
Family
AmaranthaceaeScientific Name
Amaranthus tuberculatus
Other Common Names:
common waterhemp
tall amaranth
tall waterhemp
Synonyms (former Scientific Names):
Amaranthus ambigens
Amaranthus tamariscinus
Acnida subnuda
Acnida tuberculata
Acnida concatenata
Amaranthus rudis
Acnida tamariscina
Amaranthus altissimus
Acnida altissima
Habit
Plants germinate in spring and quickly grow during the summer months. Flowering occurs in mid summer until frost and a single plant may produce thousands of tiny seed. Stems are erect to sometimes ascending, and usually grow to 3-7 feet in height.
Leaves
Leaves lack hairs, and have conspicuous veins. The petiole is usually half the blade length. Blades are oblong or narrow and much longer than wide.
Identifying Characteristics
Tall waterhemp has no hair on the stem or leaves, while most other pigweeds have some hair. This characteristic is especially evident when inspecting the newest emerging leaf on young plants. If this newest leaf is hairless, the plant is most likely tall waterhemp or Palmer amaranth. Palmer amaranth leaves, however, are short and broad with petioles that area usually at least as long as the leaf.
Flower Seed Head
Flowers are inconspicuous and produced in a terminal inflorescence containing branched spikes with numerous green, brown, or reddish flowers. Some plants produce male flowers that will have yellow stamens and lack seed and other plants produce female flowers that are usually green, often have white stigmas, and will typically expel shiny brown to black seed when beat across the palm.
Seed Fruit
Seeds are dark reddish brown to dark brown, 0.7-1 mm in diameter, and shiny. Each seed is enclosed in a papery sack (utricle) that splits in half easily dispelling the shiny seed.
Where Found
Wet areas, such as margins of rivers, ponds, marshes, lakes, and creeks, and disturbed habitats, such as agricultural fields, roadsides, and railroads.
Growth Habit
upright and nonwoody
Thorns or Spines
not present
Approximate Flower Diameter
pencil
Dominant Flower Color
green
Flower Symmetry
radial symmetery
Leaf Hairs
no hairs
Leaf Shape
oval
Leaf Arrangement
alternate
Leaf Margin
entire
Leaf Structure
simple
Leaf Stalk
shorter than leaf
Stem Hairs
no hairs
Stem Cross Section
round or oval
Milky Sap
not present
Root Structure
taproot
Life Cycle
summer annual
Ochrea
not present
Plant Type
Herb