Common Name: Giant Ragweed

General Information

Ambrosia trifida is an erect, annual plant with a stem that is usually 30 - 150cm tall, exceptionally reaching 400cm[].
The plant is harvested from the wild for local use as a medicine - the plant is sometimes also cultivated for medicinal use[].. A good quality oil can be obtained from the seeds - the plant has been suggested for commercial cultivation as a source of this oil[].
The plant is found as a weed in many areas outside its native range.

Known Hazards

The pollen of this plant is a major cause of hayfever in N. America[]. Ingesting or touching the plant can cause allergic reactions in some people[].

Botanical References

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Range

N. America - Alaska, British Colombia to Nova Scotia, south to California, northern Mexico, Texas and Florida

Habitat

Disturbed sites, waste places, damp soils; at elevations from sea level to 1,600 metres[]. Alluvial waste places, sometimes forming vast pure stands[].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual
Height	1.20 m
Pollinators	Wind
Cultivation Status	Wild

Cultivation Details

We have very little information on this species but suggest growing it in a sunny position in a well-drained soil[].
This plant is sometimes cultivated by the N. American Indians for food and medicine[].
The name Ambrosia ×helenae Rouleau applies to hybrids between A. artemisiifolia and A. trifida. Hybrids between A. bidentata and A. trifida have been recorded[].

Edible Uses

This plant was cultivated by the pre-Columbian N. American Indians, seeds found in pre-historic sites are 4 - 5 times larger than those of the present-day wild plant, which seems to indicate selective breeding by the Indians[].
The following report is for Ambrosia artemesifolia, it quite possibly also applies to this species[].

An oil is obtained from the seed. It has been suggested for edible purposes because it contains little linolenic acid[, ]. The seed contains up to 19% oil[], it has slightly better drying properties than soya bean oil[].

Medicinal

The leaves are very astringent, emetic and febrifuge[, ]. Taken internally, they are used as a tea in the treatment of pneumonia, fevers, nausea, intestinal cramps, diarrhoea and mucous discharges[].
The leaves are applied externally to insect bites and various skin complaints[].
The juice of wilted leaves is disinfectant and is applied to infected toes[].

A tea made from the roots is used in the treatment of menstrual disorders and stroke[].

The pollen is harvested commercially and manufactured into pharmaceutical preparations for the treatment of allergies to the plant[].

Other Uses

A red colour is obtained from the crushed heads[]. (This probably refers to the seed heads[].)
The sap of the plant can stain the skin red[].

Propagation

Seed - we have no details for this species but suggest sowing the seed in situ in mid spring.