Kudzu

Kudzu is a group of climbing, coiling, and trailing deciduous perennial vines. These plants belong to the genus Pueraria within the pea family, Fabaceae. While they are native to much of East Asia, Southeast Asia, and some Pacific islands, they have become a major invasive species in many other parts of the world. An invasive species is a plant that moves into a new area and causes harm to the local environment. In North America, kudzu is often considered a noxious weed because of how it affects local ecosystems.

The way kudzu grows allows it to dominate its surroundings very quickly. It spreads through vegetative reproduction using stolons, which are runners that root at the nodes to form new plants. It also spreads through rhizomes, which are underground stems. While it can spread via seeds found in pods, this is a rare occurrence. For a seed to germinate, the soil must remain soggy for five to seven days. The temperature must also stay above 20 °C (68 °F).

Kudzu causes ecological damage by outcompeting native flora for vital resources. Its primary method of competition is for sunlight. The vine grows rapidly over other plants and trees, creating a dense layer of leaves. This layer shades the plants underneath, blocking their access to light. Without enough sunlight, these native plants may die. This process can also change the soil. When kudzu invades, it makes the leaf litter more labile. This can lessen the ability of the soil to perform carbon sequestration.

The history of kudzu in the United States is quite unique. It was first introduced from Japan at the 1876 Centennial Exposition in Philadelphia. It was also displayed at the Chicago World's Fair. During the Dust Bowl era of the 1930s and 1940s, the plant was marketed to farmers as a tool to stop soil erosion. The Soil Conservation Service grew seventy million kudzu seedlings to help with this goal. They even paid $8 an acre to people who would sow the vine.

By the 1940s, kudzu cultivation reached its peak. A man named Channing Cope, known as the "kudzu kid," helped popularize the vine in the South. He started the Kudzu Club of America, which grew to 20,000 members by 1943. However, once the Soil Conservation Service stopped its payments, many farmers turned the land over to more profitable uses. The government stopped promoting the plant altogether by the 1950s. Today, kudzu is found in 32 U.S. states, ranging from the Southeast to as far north as Boston, Massachusetts.

Controlling kudzu requires targeting its most resilient parts. The most important part to destroy is the root crown. This is a fibrous knob of tissue that sits on top of the roots. These crowns can be the size of a pea or a basketball. They can weigh as much as 180 to 225 kilograms and extend twenty feet into the ground. If any part of the crown remains, the plant can grow back. Some people use mechanical methods, like cutting crowns just below ground level. Others use animals like goats or llamas to graze on the vines.

Scientists and researchers have developed several other ways to manage the vine. Some use systemic herbicides like glyphosate to kill the extensive root system. Since 1998, the U.S. Agricultural Research Service has tested a fungus called Myrothecium verrucaria as a biological herbicide. This fungus can damage kudzu very quickly. Another unique method involves using helium gas. A student named Jacob Schindler discovered that drilling holes and saturating the soil with helium can kill 98% to 100% of the plants.

Despite its reputation as a weed, kudzu has some beneficial biological traits. As a legume, it has a symbiotic relationship with nitrogen-fixing bacteria. This relationship helps increase the amount of nitrogen in the soil. Its deep taproots also help move minerals from the subsoil up to the topsoil. This can actually help improve soil quality. However, in most places where it is invasive, the damage it does to native ecosystems outweighs these benefits.