What is a grass?

Grasses are short plants with long, narrow leaves, jointed stems, and flowers that are almost always arranged in spikes. This group of plants first appeared on land more than 66 million years ago, evolving over time into the 12,000 species of grasses today. Grasses cover huge areas of land on every continent and are more widely spread than any other type of plant.

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w M e a d o Grass flowers

Anthers poke out of the flowers and bob in the wind, releasing pollen grains.

Grasses produce flower spikes with many small flowers, which are wind-pollinated. As they mature, each flower dangles its anthers in the wind, allowing millions of pollen grains to be blown away to fertilize the feathery, sticky stigmas of another grass. Since grasses do not have to attract animal pollinators, their flowers have lost their colorful petals.

Growing point ❯ Grasses can survive continual grazing by wild and farm animals because their growing point is at the base of their stem, close to the soil. When nibbling animals eat the leaves, they leave this growing point intact, allowing the plant to regrow easily.

Leaf blade ❯ Many grasses have long, thin leaves with parallel veins running down the length of each blade. Each new leaf emerges from within the base of the older blade.

Roots ❯ Grasses have very dense root systems that hold the plant in place even when being tugged at by large grazing animals. These root clusters also hold the soil together, preventing erosion.

Grass imposters

Rush This snowy woodrush has long, thin leaves that may look like those of a grass, but it is actually a rush and belongs to a related family of plants.

Seagrass These seagrasses live on the ocean floor, providing an important habitat and food source for a wide range of fish and other marine life.

Sedge Sedges are wetland plants with grasslike leaves, but you can tell them apart from grasses and rushes by their triangular stems.

Grasslands

Leaf sheaths grow at the base of each grass leaf. Wrapped around the stem, leaf sheaths prevent stems from breaking and also protect the growing point. Grassland habitats cover about a third of all land on Earth. They are found in regions too dry to support a forest but too wet to be a desert. From African savannas to North American prairies to European meadows, grasslands support a huge variety of wildlife around the world, such as the Grant’s gazelles seen here. Wildfires often sweep across grasslands, encouraging thick grass regrowth and removing tree seedlings.