Ambrosia tomentosa

Species category

Weed

Common name

skeletonleaf bur ragweed

Diagnostic characters

Planting unit

AcheneAchene:
A dry, hard, one-chambered, one-seeded indehiscent fruit, as in buckwheat (Fagopyrum) or sunflower (Helianthus). The fruit wall is not united with the seed coat.

Shape

ObovateObovate:
Inverted egg shaped with apical end the broadest.

Size

  • Length: 6 mm
  • Width: 3 mm
  • Thickness: 3 mm

Color

Brown

Texture

Smooth

Other structures

Large spines on apicalApical:
The distal end of the fruit or seed away from the point of attachment or attachment scar.
half

Identification notes

Seed type is best described as an acheneAchene:
A dry, hard, one-chambered, one-seeded indehiscent fruit, as in buckwheat (Fagopyrum) or sunflower (Helianthus). The fruit wall is not united with the seed coat.
enclosed in an involucreInvolucre:
A number of bracts (often leaf-like) that subtend an inflorescence such as the head in sunflowers.
. Midsize of the bursages. Usually with two terminal spikesSpike:
Has a strong central axis (rachis) on which flowers or spikelets are directly attached (sessile), e.g. wheatgrasses.
.

Noxious weed seed categories

State Noxious Weed: Colorado, Hawaii, Idaho, Nebraska, Wyoming

AOSA examination list

Not included

Nomenclature

Family

Asteraceae

Valid name

Ambrosia tomentosa Nutt.

Synonyms

Franseria discolor Nutt.
Franseria tomentosa (Nutt.) A. Nelson, non A. Gray
Gaertneria discolor (Nutt.) Kuntze
Gaertneria tomentosa (Nutt.) A. Heller

 Ambrosia tomentosa.  Seed type is best described as an achene enclosed in an involucre. Mid-sized bursae. Usually with two terminal spikes.
Ambrosia tomentosa. Seed type is best described as an achene enclosed in an involucre. Mid-sized bursae. Usually with two terminal spikes.
From Left to Right: 1.  Ambrosia tomentosa  2.  Ambrosia grayi  3.  Ambrosia confertiflora .
From Left to Right: 1. Ambrosia tomentosa 2. Ambrosia grayi 3. Ambrosia confertiflora.