Unlike animals, plants typically cannot move. However, there is a type of plant that can move when wet: the Pili grass.
Pili grass (scientific name Heteropogon contortus), also known as black spear grass, is a type of tropical grass widely distributed in various regions around the world, from South Africa, South Asia, and Northern Australia to the southern parts of North America and even the Hawaiian Islands (USA)…
Pili grass can grow up to 1.5 meters tall. This grass adapts well to a variety of climate conditions, from dry to humid. While Pili grass often grows wild, it is sometimes cultivated by humans for landscaping or as fodder for livestock. Pili grass clumps also play a significant role in preventing soil erosion. Native Hawaiians even use Pili grass for thatching roofs.
Pili grass seeds (left) and developed grass clumps. (Photo: Getty).
The name Pili means “to cling tightly” or “to adhere” in the language of Native Hawaiians, referring to the way the seeds of this grass disperse in nature. Pili grass seeds are dispersed by the wind or by animals.
The seeds of Pili grass have a unique shape, featuring a pointed end and a long body. Notably, Pili grass seeds can “wake up” upon contact with water and moisture.
Pili grass used by Native Hawaiians for thatching roofs. (Photo: ESS).
When wet or exposed to suitable humidity, the seeds of Pili grass will contract and bend continuously, creating movement. This allows the Pili grass seeds to work their way into cracks or small holes in dry soil, enabling them to develop into grass plants.
In some cases, Pili grass seeds may also cling tightly to the fur and skin of wild animals, allowing the seeds to disperse further.
Pili grass seeds move when they encounter water. (Video: Lê Anh Tuấn).
Sometimes, Pili grass seeds can become lodged in the open wounds of wild animals, causing these animals to suffer from infections that can lead to death. In some cases, the seeds may penetrate deep into the bodies of animals through open wounds, causing them significant pain and resulting in death shortly thereafter.
This unique dispersal method and the special ability of the seeds to “wake up” have allowed Pili grass to adapt and thrive in various living conditions, including harsh environments.
