Ragweed is a North American plant in the genus Ambrosia which has spread to almost every region of the Earth. Plants in this genus famously produce huge amounts of pollen, much to the dismay of people who suffer from allergies, and ragweed pollen contributes significantly to hay fever and other allergies all over the world. It is essentially impossible to control ragweed, since it is tenacious, hardy, and quite sneaky, for a plant.
Ragweeds vary considerably in appearance. They have lobed to toothed leaves which can be silvery to gray-green, with rough stems and small clusters of greenish flowers. The pollen of ragweed plants is very lightweight, designed for dissemination on the wind, and these plants produce a lot of pollen each year, so the air can be heavily laden with pollen in some regions of the world on a windy day. Ragweed pollen can even enter the jet stream, traveling considerable distances before it returns to earth.
Depending on the species and the climate, ragweed can be an annual or a perennial. Some species cling close to the ground, often hiding under larger plants which are sometimes blamed for seasonal allergies, while others become subshrubs or even full shrubs. This plant can be choked out with thick groundcovers, but it also springs up wherever the soil is disturbed or of poor quality. Vacant lots, roadside ditches, abandoned fields, and poorly-maintained gardens are all havens for ragweed, and the plant is often the first to appear when a plot of land has been cleared.
Many gardeners treat ragweed as a noxious invasive, because it can spread rapidly if given a chance to do so, and it is associated with health problems. While there are some herbicides which can treat ragweed, the best way to cope with the plant is to establish hardy groundcovers, and to pull up ragweed whenever it is spotted. Neighbors should also be encouraged to get proactive about this member of the sunflower family, to reduce the pollen load in the air.
In addition to causing allergies, ragweed has also been linked with skin irritation, especially in people with sensitive skin. Ragweed often hides in hay fields and other locations frequented by people, and it can raise large welts, rashes, and rough spots on people with pale or delicate skin.
People with allergies should make a habit of checking pollen counts in the spring and summer to determine the condition of the air before going outside. Flushing out the nose with saline rinses periodically over the course of the day can also help to reduce seasonal allergies by flushing pollen and other irritants out of the nose. Nasal irrigation kits designed for this purpose are available at many drugstores. For pollen-related eye irritation, gentle eye rinses are very helpful, as warm warm moist compresses to soothe aching eyes.