There are about 40 different types of ragweed plants in the family of Asteraceae, and most of them are native to North America. Ragweeds are common everywhere in the northern hemisphere. They are often classified as weeds, or nuisance plants. Extremely common in the northeastern and midwestern regions of North America, ragweed plants are perhaps best known as a cause of seasonal allergies. While there are quite a few different varieties, there are a few that are more prevalent and numerous than others, like the common ragweed and the giant ragweed.
Asteraceae is also known as the sunflower family. These plants are characterized by rough, hairy stems with either divided or lobed leaves. The scientific name for ragweed is Ambrosia, which probably refers to their tenaciousness, and should not be confused with the dessert or the legendary food of the Greek gods.
Many ragweed plants produce allergens that cause hayfever suffers to show symptoms. Hayfever usually occurs when plants are producing pollen, the substance that causes allergic reactions, which is at its peak, in North America, during August and September. Pollen counts are usually the highest right after the sun rises for the day. When this substance is inhaled by an allergy sufferer, his body identifies it as a potentially harmful foreign agent, and mounts an immune response. The allergy sufferer may then begin to exhibit symptoms like itchy and watery eyes, runny nose, and sneezing.
The common ragweed plant, Ambrosia artemisiifolia, is so named because it is the most common of all the ragweed plants in North America. It is an annual, which means it dies after it produces seeds, so only lives about a year. The plant is also very invasive and has spread to Europe and Japan. It is also known to be a very strong allergen for those who suffer from seasonal allergies.
The giant ragweed plant, Ambrosia trifida, is one of the most competitive ragweed plants in North America. A competitive plant is one that will choke out other plants, and take over areas and resources. As a weed, it is a particular bane to farmers. It can reduce the yields of crops like corn and soybeans by 50% or more.
While it is probably impossible to eradicate these invasive plants completely, they can be controlled. An annual ragweed plant, like either the giant or common ragweed plant, can easily be killed off if it is mowed or chopped down. To help allergy sufferers, mowing down fields of the plants before they flower may greatly help reduce the amount of pollen that is present in the air.
Some plants that bloom in late summer or early fall are often mistaken as ragweed plants. For example, many people falsely label goldenrod as a ragweed plant. Goldenrod is a perennial with bright yellow flowers. It is not as invasive and does not cause allergy issues like many of the ragweed plants.