Despised ragweed can be interesting plants
September 16, 2001

Ragweed are common plants that are "despised" because of their abundance in cultivated and disturbed land, and because their abundant pollen, this time of year, causes hay fever.

If these two faults can be overlooked, ragweed are extremely interesting plants, their abundance making them available for closer study. Allergy sufferers are excused!

Ragweed are member of the composite family which includes asters, daises, dandelions, characterized by having disk flowers. Ragweed are a member of one of the tribes of composites with the name "Ambrosieae." Ironically, the scientific name for ragweed is "Ambosia!" The common ragweed is ambrosia artemisifolia because the foliage resembles the artemisias (wormwoods).

there are three species of ragweed in Wisconsin. The giant, the common, and a perennial variety. Although many of our common "weeds" originally came from overseas, the ragweed are native Americans that were probably originated from arid and semi-arid regions in southwestern North America, where primitive species are still abundant.

These species often have spines that allow them to be dispersed by animals. The more advanced species, such as the present common ragweed have adapted to being spread in other ways.

When European settlers opened up the land by cultivation, the ragweed were ready to take over. Seeds that pass through birds are still viable and can be spread in that manner. The seeds usually fall in close proximity to the parent plant, where they join those that might have been burled in the soil for as long as 40 years, awaiting a turnover disturbance.

Whey the surplus pollen that causes a problem? The plants are pollinated by wind, and an excess is needed. Examine the flower "tails" of a ragweed. The top portion contains the staminate (male) blossoms which contain five little compartments packed with pollen. The pistillate part of the plant is lower on the stem and can be seen as a hard little spiny burr with very noticeable beaks through which the stigmatic lobes project.

The pollen-packed stamens have a sterile female part in their center. Its only purpose is to push out the pollen. This airborne pollen drifting through the air is the cause of the most serious natural air pollutant in North America.

All ragweed are found in open habitats. The common ragweed is an annual. In a few years, if the soil is undisturbed, the plants are replaced by perennial species, like goldenrod.

there is little good to be said about the ragweed unless one happens to know about their value to wildlife. The seeds are rich in oil, and production per plant is enormous. They provide food for game birds, some of our best loved songbirds such as goldfinches, song sparrows, and juncos, as well as small mammals---especially during the winter months as the seeds stay on the plants into the winter and are an available food source.

As humans continue to provide more open and disturbed space for ragweed, the "good" for the birds and the "bad" for hay fever sufferers will be an everlasting plus and minus for ragweed.