More than Just Your Average Ragweed


Parthenium hysterophorus goes by many common names of which Ragweed Parthenium, Famine Weed, Feverfew, and Congress Grass are but a few.

Recently this fairly uncommonly seen but dangerous invasive plant was discovered thriving at Toni Robinson Waterfront Trail between Vero Beach and Sebastian. The noxious weed which is native to Mexico and Central America was in full flower and fortunately approximately 60 fully flowered plants were removed before seeding. This plant moves into disturbed areas and was making itself at home in an area that had been cleared of Brazilian Pepper and which is being closely monitored to observe the native (and nonnative plants) moving in.

This invader has a litany of harmful effects that go beyond the typical threat to native flora and fauna. Via a process known as allelopathy, he roots emit chemical agents which inhibit the growth of nearby plants. As is the case with some other invasive plants this process results in a dense monocultural mass of the one species. Parthenium Ragweed is very prolific and a single plant can produce 15,000 seeds.

Beyond being invasive, this noxious weed is dangerous to livestock and other animals that may feed on it. The monocultural aspect of its growth reduces fodder further encouraging livestock to eat it.

Human health can be very negatively impacted. Repeated contact with the plant can result in very painful and serious dermatitis with extremely unsightly and painful blistering. It can cause asthma, eye problems, and hay fever. Although this poison plant is not always fatal to the livestock that ingests it, meat and milk from such animals is dangerous for human consumption.

The rapidly spreading distribution of this plant worldwide is both amazing and alarming. It has caused enormous problems in Africa, India, and Australia.

When we find this plant here in Florida (or anyplace) it should be safely removed as quickly into the infestation as possible with future follow up.

Article and photo by Ken Gonyo.

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