Ambrosia trifida

This huge plant is probably an allergy sufferer's worst nightmare. It has some ecological value to various moths, but otherwise is less important than Ambrosia artemesiifolia (Common Ragweed). Giant Ragweed can be distinguished from other Ambrosia spp. (Ragweeds) by its palmately lobed leaves; other Ragweeds have leaves that are pinnatifid or bipinnatifid. The name of this genus of plants refers to ambrosia, "the food of the gods" in antiquity. This seems like a strange name for a group of unattractive plants, unless it refers to the value of the seeds of certain species from a bird's point of view. Return

This is a native annual plant from 3-12' tall, branching occasionally. The green stems are covered with white hairs. The opposite leaves are up to 12" long and 8" across. The larger leaves are divided into 3 or 5 lobes, usually serrated along the margins, and have long petioles that are sometimes winged. The smaller leaves near the base of an inflorescence are lanceolate and often hairy underneath. Many of the upper stems terminate in a cylindrical spike of flowers, about 3-6" long, with one or more smaller spikes near its base. The small flowers are are yellowish green and devoid of petals and sepals. They occur in small drooping clusters less than ¼" across on short pedicels, and are densely arranged all around each spike. The fine pollen of the male flowers is easily carried aloft by the wind. This typically occurs during late summer or early fall. The seeds are large, tough-coated, and remain viable in the soil for several years. The root system is fibrous. Cultivation

Giant Ragweed is a common plant that occurs in every county of Illinois (see Distribution Map). It can be found in disturbed areas of moist to mesic black soil prairies, especially along the margins near woodlands or fields. Other native habitats include disturbed areas of moist clay prairies, meadows in woodland areas or near rivers, thickets, and woodland borders. In more developed areas, it occurs in vacant lots, cropland, abandoned fields, poorly drained waste areas, areas along roadsides and railroads, and fence rows. Faunal Associations

Ambrosia trifida var. trifida :
Canada (North America)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Ambrosia trifida fo. trifida :
Canada (North America)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Ambrosia trifida var. texana Scheele:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Ambrosia aptera DC.:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Ambrosia trifida L.:
Canada (North America)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Annuals, 30–150(–400+) cm. Stems erect. Leaves mostly opposite; petioles 10–30(–70+) mm; blades rounded-deltate to ovate or elliptic, 40–150(–250+) × 30–70(–200+) mm, usually some blades palmately 3(–5)-lobed, bases truncate to cuneate (sometimes decurrent onto petioles), margins usually toothed, rarely entire, abaxial and adaxial faces ± scabrellous and gland-dotted. Pistillate heads clustered, proximal to staminates; florets 1. Staminate heads: peduncles 1–3+ mm; involucres ± saucer-shaped, 2–4 mm diam., scabrellous (often with 1–3 black nerves); florets 3–25+. Burs: bodies ± pyramidal, 3–5(–7+) mm, glabrous or glabrate, spines 4–5, ± distal, ± acerose, 0.5–1 mm, tips straight (bases ± decurrent as ribs). 2n = 24, 48.

Ambrosia aptera de Candolle; A. trifida var. integrifolia (Muhlenberg ex Willdenow) Torrey & A. Gray; A. trifida var. texana Scheele

Giant Ragweed is a common plant that occurs in every county of Illinois (see Distribution Map). It can be found in disturbed areas of moist to mesic black soil prairies, especially along the margins near woodlands or fields. Other native habitats include disturbed areas of moist clay prairies, meadows in woodland areas or near rivers, thickets, and woodland borders. In more developed areas, it occurs in vacant lots, cropland, abandoned fields, poorly drained waste areas, areas along roadsides and railroads, and fence rows. Faunal Associations

Ambrosia trifida (Giant Ragweed)
(Wind-pollinated; honeybees collect pollen, while the wasp merely explores the flowers; observations are from Robertson)

Bees (short-tongued)
Apidae (Apinae): Apis mellifera cp fq

Wasps
Vespidae: Vespula germanica exp

The following is a representative barcode sequence, the centroid of all available sequences for this species.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 5
Specimens with Barcodes: 13
Species With Barcodes: 1

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: T5 - Secure

United States

Rounded National Status Rank: NNR - Unranked

Rounded Global Status Rank: T5 - Secure

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure