There are twenty-four species of ragweeds or bursages native to North America. Most are plants of upland to arid soils. The most notorious and widely found is annual ragweed (Ambrosia artemisiifolia Linnaeus), the cause of so many miserable cases of 'hayfever' in the late summer and early autumn.
Annual ragweed is a colonizer, a weed. It is one of the first plants to establish on disturbed soils or fallow fields. Ragweed seeds germinate rapidly on or near the surface of the soil emerging before most other plants. The tiny cotyledons (seed leaves) turn green and begin photosynthesizing within hours of germination. The seedlings are tolerant of bright sunlight, varying temperatures, and drying soils. Ragweed also produces an allelopathic compound, coronopilin, which reduces the vigor of other plants growing in the vicinity.
If the field is used the following year, annual ragweed often out-competes the planted crop. It has evolved an ability to resist herbicides making it an expensive nuisance for farmers. One of the best controls of the plant is to mow just before it flowers. But mowing is not an alternative when the plant is growing among crops.
Unlike other members of the Asteraceae, the daisy family, annual ragweed has small drab green flowers. The plant is monoecious; staminate (male) and pistillate (female) flowers are borne separately on the same plant. The staminate flowers produce copious amounts of pollen which is carried on the wind. Annual ragweed blooms about the same time as goldenrod, but the very visible flowers of goldenrod got the blame for the runny nose, congestion and sneezing of allergic rhinitis. Goldenrod, though, is insect pollinated; its pollen does not float in the wind.
As odious as ragweed is, then, its botanical name is quirky. The species epithet fits, artemisiifolia "with foliage like artemisia (wormwood)". But the Greek Ambrosia was a food or unguent that imparted immortality and, hence, was reserved for the gods. Frankly, the gods can have it.
(Compiled from: Composition of Scientific Words, Roland Wilbur Brown, Smithsonian Institution Press, Washington, DC, 1991; "Ambrosia artemisiifolia L.", James A. Duke, Phytochemical and Ethnobotanical Databases, Agricultural Research Service, and "Ecophysiology of Ambrosia artemisiifolia: A Successional Dominant", F.A. Bazzaz, Ecology: Vol. 55, No. 1, 1974)
