Waterhemp

Amaranthus tuberculatus

Leaves: Long and linear and sometimes oval-shaped. Leaf petioles are shorter or no longer than the leaf blades.

Stems: Smooth (not hairy) and green, red, green-red striped.

Height: Can grow very tall, up to 10 feet in, especially in competition with corn.

Flowers: Male and female flowers on separate plants. Flowers are primarily produced on long (up to 1-2 feet or more, in length) terminal flower heads. Female flowers do not have sharp bracts associated with them. Waterhemp flowers clusters are more widely spaced apart than those of Palmer amaranth.

Herbicide resistances in US: WSSA Groups 2, 4, 5, 9, 14, 15, 27.

waterhemp leaves are linear — Waterhemp has long, linear and sometimes oval-shaped leaves.

Linear leaves of waterhemp — Waterhemp has long, linear and sometimes oval-shaped leaves.

Images above: Waterhemp has long, linear and sometimes oval-shaped leaves..

waterhemp leaves — Waterhemp has linear leaves.

Images above: Waterhemp has long, linear and sometimes oval-shaped leaves..

Images above: Smooth (hairless) waterhemp stems (left) can sometimes be mistaken for Palmer amaranth stems (right).

Image above: Waterhemp plant.

male and female waterhemp flowers — Male (L) and female (R) waterhemp flowers

male waterhemp flowers — Male waterhemp flowers. Note the spaces between clusters on the left.

Images above left: Waterhemp produces flowers primarily on long (up to 1- to 2-feet-long or more) terminal flower heads (male on left, female on right). Images above right: Male waterhemp flowers. Note the spaces between clusters on the left.

Image above: Waterhemp cotyledons (left) and seedling (right).

soybean field with herbicide resistant waterhemp — Herbicide resistant waterhemp in soybean.

Image above: Herbicide resistant waterhemp in soybean.

Waterhemp vs. Palmer amaranth (leaves)

Waterhemp (lower left) vs. Palmer (upper right) leaves

Left image above: Waterhemp (lower left) vs. Palmer amaranth (upper right) leaves. Right image above: Waterhemp (left) vs Palmer amaranth (right) leaves

Leaves of Palmer amaranth are more distinctly, diamond-shaped as compared to waterhemp, which has long and linear leaves which can sometimes approach oval-shaped.

Waterhemp vs. Palmer amaranth (flowers)

Waterhemp and Palmer amaranth female flowers (right). — Female flowers of Palmer amaranth (left) vs waterhemp (right).

Above left image: Waterhemp female flowers (left) and Palmer amaranth female flowers (right).

Male waterhemp flowers will have anthers full of yellow pollen grains. These may be best observed in early morning before the sacs break open and pollen is released. Female flowers will have white, branched stigmas, which catch the pollen. Waterhemp flowers are less tightly clustered on the stem compared to Palmer amaranth. Palmer amaranth female flowers will have sharp, stiff bracts.