Ambrosia psilostachya

Rodents eat the seeds of Ambrosia psilostachya , including the Thirteen-Lined Ground Squirrel and Prairie Vole. Mammalian herbivores eat the bitter foliage to a limited extent. Because the caterpillars of various moths feed on its foliage, and many songbirds and upland gamebirds eat its seeds throughout the winter, this plant has high ecological value. This species may have allelopathic or other inhibitory effects on other pioneer plant species.
Photo Credit: © Joseph M. DiTomaso, University of California - Davis, Bugwood.org.
Ambrosia psilostachya
Common Name: cuman ragweed
Other Common Names: perennial ragweed
Plant Functional Group: Forb
Class > Order > Family: Magnoliopsida > Asterales > Asteraceae
What does the species look like?

Cuman ragweed is an erect, annual or perennial, herbaceous plant with little branching. It grows between 0.75 and 3.5 feet tall, but occasionally up to 6 feet tall. Small, inconspicuous male and female flowers occur separately, along stalks, on the same plant, and pollination occurs by wind.

Cuman ragweed grows in grasslands, savannas, woodlands, and riparian areas, and also in disturbed and waste areas, travel corridors, and dry fields. It typically occurs on dry, sandy soils.
Where is the species found?
States & Provinces
AB, AL, AR, AZ, BC, CA, CO, CT, FL, GA, IA, ID, IL, IN, KS, LA, MA, MB, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NM, NS, NV, NY, OH, OK, ON, OR, PA, PE, QC, SC, SD, SK, TN, TX, UT, VT, WA, WI, WY
Special Considerations for Observing

If drought seems to be the cause of leaf senescence for a plant, please make a comment about it for that observation.
Which phenophases should I observe?
Do you see...?
Leaves Initial growth
New growth of the plant is visible after a period of no growth (winter or drought), either from above-ground buds with green tips, or new green or white shoots breaking through the soil surface. Growth is considered "initial" on each bud or shoot until the first leaf has fully unfolded. For seedlings, "initial" growth includes the presence of the one or two small, round or elongated leaves (cotyledons) before the first true leaf has unfolded.
More...


Leaves
One or more live, fully unfolded leaves are visible on the plant. For seedlings, consider only true leaves and do not count the one or two small, round or elongated leaves (cotyledons) that are found on the stem almost immediately after the seedling germinates. Do not include fully dried or dead leaves.
More...


Flowers Flowers or flower buds
One or more fresh open or unopened flowers or flower buds are visible on the plant. Include flower buds or inflorescences that are swelling or expanding, but do not include those that are tightly closed and not actively growing (dormant). Also do not include wilted or dried flowers.
More...

How many flowers and flower buds are present? For species in which individual flowers are clustered in flower heads, spikes or catkins (inflorescences), simply estimate the number of flower heads, spikes or catkins and not the number of individual flowers.

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • More than 1,000
Open flowers
One or more open, fresh flowers are visible on the plant. Flowers are considered "open" when the reproductive parts (male stamens or female pistils) are visible between or within unfolded or open flower parts (petals, floral tubes or sepals). Do not include wilted or dried flowers.
More...

What percentage of all fresh flowers (buds plus unopened plus open) on the plant are open? For species in which individual flowers are clustered in flower heads, spikes or catkins (inflorescences), estimate the percentage of all individual flowers that are open.

  • Less than 5%
  • 5-24%
  • 25-49%
  • 50-74%
  • 75-94%
  • 95% or more
Pollen release
One or more flowers on the plant release visible pollen grains when gently shaken or blown into your palm or onto a dark surface.
More...

How much pollen is released?

  • Little: Only a few grains are released.
  • Some: Many grains are released.
  • Lots: A layer of pollen covers your palm, or a cloud of pollen can be seen in the air when the wind blows

Fruits Fruits
One or more fruits are visible on the plant. For Ambrosia psilostachya, the fruit is a small burr that changes from green to tan, reddish-brown or brown and drops from the plant.
More...

How many fruits are present?

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • More than 1,000
Ripe fruits
One or more ripe fruits are visible on the plant. For Ambrosia psilostachya, a fruit is considered ripe when it has turned tan, reddish-brown or brown and readily drops from the plant when touched.
More...

What percentage of all fruits (unripe plus ripe) on the plant are ripe?

  • Less than 5%
  • 5-24%
  • 25-49%
  • 50-74%
  • 75-94%
  • 95% or more
Recent fruit or seed drop
One or more mature fruits or seeds have dropped or been removed from the plant since your last visit. Do not include obviously immature fruits that have dropped before ripening, such as in a heavy rain or wind, or empty fruits that had long ago dropped all of their seeds but remained on the plant.
More...

How many mature fruits have dropped seeds or have completely dropped or been removed from the plant since your last visit?

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • More than 1,000
What do these phenophases look like?

There is currently no photoguide available for this species. If you'd like help us create one, use the guidance document and species template provided here. Then send it via email to education@usanpn.org when it is complete.

USDA PLANTS profile for cuman ragweed (USDA Symbol: AMPS )