List of the 5 Most Dangerous Invasive Plants

Invasive plants are everywhere! These plants aren’t native to the areas they end up in, this creates problems for local ecosystems. Invasive plants can also be dangerous to humans, all parts of the hemlock plant are poisonous. Hemlock is known for killing livestock and pets. Many of these dangerous invasive plants spread quickly and inhibit the growth of other native plants near them, leaving a trail of destruction in their path.

Giant Hogweed - Invasive Plants

Heracleum Mantegazzianum

You do not want to touch this plant! It causes a painful burning sensation, blistering, and scaring. After the sap touches your skin, it takes about 24-48 hours before it starts to do damage. Giant Hogweed is federally regulated under the United States Department of Agriculture “Noxious Weeds Program”, making it illegal without a special permit. If you know you’ve come into contact with giant hogweed, take a shower as soon as possible and stay out of the sunlight for 48 hours.

Witchweed - Parasitic Invasive Plants


This is a parasitic plant that kills agricultural crops like sugarcane, beans, corn, and rice. Witchweed attaches itself to the root systems of other plants. They are dangerous to many types of crops because they can produce 90,000 to 500,000 seeds per plant! The seeds can stay hidden in the soil for many years making it difficult to eliminate them all. Witchweed is one of the most destructive plants in Africa, resulting in 13 billion dollars of losses every year. This plant is a major threat to global food security.

Hydrilla / Waterthyme - Aquatic Invasive Plants

Hydrilla verticillata

Hydrilla is known for being a huge problem. It’s an aggressive aquatic plant that can be found in most of the US. When hydrilla starts growing in a lake, it often ends up creating a monoculture by starving out all of the other species of aquatic plants around it. Hydrilla has caused tons of environmental, ecological, and economic damage across the world. Hydrilla can take so much oxygen from water reservoirs that it can kill fish populations. Hydrilla is edible if prepared correctly, but be careful because I’ve read that it can absorb mercury, cadmium, chromium, and lead from polluted water sources.

Poison Hemlock - Poisonous Invasive Plants

Conium maculatum

Hemlock is a noxious weed that is so dangerous that many people recommend handling it with gloves to avoid exposure to its poison. Touching this plant can cause burning on the skin. Sometimes this plant is mistaken for parsnip or parsley, causing a potentially deadly accident if eaten. Poison Hemlock contains chemicals like coniine and γ-conicein that can cause respiratory paralysis, leading to death. This plant also kills livestock and pets, so be on the lookout around your property. Hemlock is in the carrot family of apiaceae. It can grow up to 10 feet tall. Here is a video on how to identify poison hemlock.

Chicken Tree - Poisonous Invasive Trees

Triadica sebifera

This tree is mainly known as the Chinese tallow, it’s common around my area of the gulf coast but it’s native to China and Taiwan. The chicken tree is in the Texas Department of Agriculture’s noxious plant program, making it illegal to import or sell in the state. The leaves and berries contain a milky white sap that is poisonous to pets and cattle. Benjamin Franklin brought the seeds of the chicken tree from southern Vietnam to the US in 1772. I notice many articles online talking about how this tree was grown for its oil inside of the seeds, which is used in the manufacturing of soap, candles, cloth, and biofuel. I even found a whole website dedicated to the subject of chicken tree biofuel here. This video below will help you identify the chicken tree if you want to know what they look like.

Invasive Insects & Animals

Thanks for checking out my post on dangerous invasive plants! For information on invasive animals and insects, check out our discussion here.