Ragweed (4)
Ragweed pollen is considered the number one cause of hay fever in the late-summer and fall. Each plant can produce over a billion grains of pollen per season which occurs from mid-August until frost. Ragweed flourishes during dry hot summers.
Common Ragweed
Ambrosia artemisiifolia
Family:
Sunflower (Asteraceae)
AKA:
Annual Ragweed
Photo taken on:
July 31, 2011
Location:
Heron Lake Area, NM
Life Zones:
Plains and foothills
Habitat:
Waste and disturbed areas
Grows 1 to 3ft tall with deeply cut, softly hairy leaves. Flowers are tiny and yellow-green. Male flowers grow above the female flowers on the same spike.
Seeds are enclosed in a hard bur. Leaves are more divided than Western Ragweed.
Flora of North America reference.
Western Ragweed
Ambrosia psilostachya (A. coronopifolia)
Family:
Sunflower (Asteraceae)
AKA:
Western Ragwort, Perennial Ragweed
Photo taken on:
September 17, 2011
Location:
Los Alamos, NM
Life Zones:
Plains and foothills
Habitat:
Dry waste areas, roadsides
Grows 1 to 2ft with lobed but broader leaves than the other Ragweeds. Like other Ragweeds, male flowers grow above the female flower heads. The fruits are not spiny.
Flora of North America reference.
Flatspine Bur Ragweed
Ambrosia acanthicarpa
Family:
Sunflower (Asteraceae)
AKA:
Annual Bursage, Bur Ragweed
Photo taken on:
September 17, 2011
Location:
Los Alamos, NM
Life Zones:
Plains and foothills
Habitat:
Dry waste areas, roadsides
Grows to 2ft erect or sprawling, with deeply lobed leaves. The male flowers are small and inconspicuous with a dark strip on the phyllaries. The fruits are very spiny and painful to touch.
Flora of North America reference.
Skeletonleaf Bursage
Ambrosia tomentosa
Family:
Sunflower (Asteraceae)
AKA:
Bursage, Skeletonleaf Bur Ragweed
Photo taken on:
September 4, 2011
Location:
Los Alamos, NM
Life Zones:
Plains and foothills
Habitat:
Disturbed areas, roadsides
Grows up to 3 feet tall. Leaves are up to 5 inches long,
and very deeply lobed with coarsely toothed margins. The upper leaf
surface is greenish-gray and may have rough hairs; the lower surface is
white with short, dense hairs. Male flowers hang in umbels from the top
portion of the stem.
Female flower heads are spiny burr-like structures in the leaf axils. Fruits are 2-seeded, light brown burs with up to 10 short spines.
Flora of North America reference.