great ragweed
Family
AsteraceaeScientific Name
Ambrosia trifida
Other Common Names:
giant ragweed
Habit
This erect summer annual flowers from July through September.
Leaves
The opposite leaves are palmately lobed with 3 lobes, although it may occasionally have 5, or be simple. Each lobe is lanceolate shaped, and have toothed margins. The lower leaves are more deeply lobed, while the upper leaves tend to be simple. Both the leaves and the stem are rough and hairy
Identifying Characteristics
This plant can be differentiated by it's opposite leaves, and its crown shaped achene.
Flower Seed Head
The small greenish flowers occur in long racemes, and are divided by male and female flowers. The male flowers occur on the ends of long racemes, while female flowers are found at the base of the racemes, and at the leaf axils.
Seed Fruit
Each seed is enclosed in a 6 to 12 mm long black achene. The achene is crown shaped, with a long central spike surrounded by 5 shorter points.
Where Found
This plant prefers moist soils in full sun or light shade. It can be found growing in ditches, low lying fields, and other areas that tend to collect water. In dry conditions, or in poor soils, the plant will be smaller and somewhat wilted.
Growth Habit
upright and nonwoody
Thorns or Spines
not present
Approximate Flower Diameter
Varies:
pencil,
dime
Dominant Flower Color
green
Flower Symmetry
bilateral symmetry
Leaf Hairs
has hairs
Leaf Shape
lance
Leaf Arrangement
opposite
Leaf Margin
serrated
Leaf Structure
simple
Leaf Stalk
shorter than leaf
Stem Hairs
has hairs
Stem Cross Section
round or oval
Milky Sap
not present
Root Structure
Varies:
fibrous,
taproot
Life Cycle
summer annual
Ochrea
not present
Plant Type
Herb