Ambrosia determination help page

You have found a plant and want to know if it is indeed common ragweed (Ambrosia artemisiifolia). Please tick the appropriate responses. (The radio buttons will not send any information anywhere)

Our Swiss colleagues at www.ambrosia.ch have published a useful page that helps to identify Ambrosia artemisiifolia by going through a small questionnaire. This page is available there in German, French and Italian. We thank our Swiss colleagues who have allowed us to implement this page in English and to use the pictures.

Questions about the plant you found

Stem (shoot)

Is the stem round in diameter? Yes No
Is the stem hairy? Yes No
Is the stem filled and not hollow? Yes No

If all questions are answered with “yes”: go to the next set of questions.
If at least one question is answered “no”: most likely you have not found Ambrosia artemisiifolia. Please look at this external page on confusing species.

Leaf

Does the top and underside of the leaf have nearly the same colour? Yes No
Are the veins whitish? Yes No
The leaf is divided into many lobes, which are themselves often divided to the middle rib? Yes No
Does the tip of the leaf lobes have fine tips? Yes No
8_blatt_mit_siel

The leaf is pinnate, that is, it has small tabs which are cut down to the petiole. The leaves have a long petiole. The individual lobes in turn are cut deep.

7_blatt_nervatur_stiel

Leaves are deep green with whitish veins.

If all questions are answered with “yes”: go to the next set of questions.

If at least one question is answered “no”: most likely you have not found Ambrosia artemisiifolia. Please look at this external page on confusing species.

Flowers

Does the stem have tips of branches and clusters of small, green, bell-shaped flowers? Yes No
Does the flower show bright dots or yellow pollen dust? Yes No
Are there small organs similar to flowers in some leaf axils of the plant ? Yes No
Male, bell-shaped flowers at the branch tips

Male, bell-shaped flowers at the branch tips

Yellow pollen

Yellow pollen

Female flowers in the leaf axils

Female flowers in the leaf axils

If more than two questions were answered “no”:

most likely you have not found Ambrosia artemisiifolia. Please look at this external page on confusing species.

If at least 2 questions of this last section were answered with “yes” and all questions of sections “stem” and “leaf” with “yes”: Most likely you are holding Ambrosia artemisiifolia in your (gloved) hands.