The oil-rich fruits and seeds of the ragweed persist into winter and are an important food for the bobwhite quail; they are also relished by songbirds and upland game birds. Cattle, however, have symptoms after eating the stems and leaves. An essential oil of this plant acts as an antimicrobial agent, having antibacterial and antifungal compounds. Yet this species causes many people to suffer with hay fever as its prolific pollen becomes wind-borne.
Annual ragweed is an erect, annual, herbaceous plant that is much-branched along a somewhat hairy stem. It grows 0.25 to 4 feet tall, or occasionally up to 6 feet tall. Small, inconspicuous male and female flowers occur separately, along stalks, on the same plant. Pollination occurs by wind. Annual ragweed grows in wet to dry soils on disturbed sites such as travel corridors, waterways, agricultural and fallow fields, construction sites, and urban areas.
Annual ragweed is a USA-NPN calibration plant species. Calibration species have broad distributions and are ecologically or economically important. The NPN integrates observations on calibration species to get "the big picture" of plant responses to climate across the nation. In addition, this species is an allergen. Observations on its phenology will provide valuable information to benefit people with allergies and the public health community.
If drought seems to be the cause of leaf senescence for a plant, please make a comment to that effect.
This species has separate male and female flowers. If you know whether the flowers you are observing are male or female (or both), please make a comment to that effect.
Do you see...?
Initial growth New growth of the plant is visible, 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. 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 leaves (cotyledons) that are found on the stem almost immediately after the seedling emerges. Do not include dried or dead leaves. More...
Flowers One or more fresh flowers or flower heads (inflorescences) are visible on the plant. Flower heads include many small flowers that usually do not open all at once. Do not include wilted or dried flowers that remain on the plant, or heads whose flowers have all wilted or dried.
How many fresh flowers or flower heads are present?
Less than 3
3 to 10
More than 10
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 unfolded or open flower parts. Do not include wilted or dried flowers that remain on the plant.
How many fresh flowers are open?
Pollen release One or more flowers on the plant release pollen when gently shaken or blown.
How many flowers release pollen?
Fruits One or more fresh fruits are visible on the plant.
How many fresh fruits are present?
Ripe fruits One or more ripe fruits are visible on the plant.
How many fruits are ripe?
Recent fruit drop One or more fresh 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.
How many mature fruits have dropped?
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