The grass family (Poaceae)
From providing our breakfast cereals to fuelling our cars, grasses are some of the most economically important plants. For instance just three cereals – maize, wheat and rice – provide nearly two-thirds of the calories and half the protein consumed by the world’s population.
Types of grass
There are nearly 11,000 different species of grass; most are perennials that regrow from the root stock each year. Except for the woody bamboos, grasses are generally herbaceous plants.
Each grass leaf has two parts: a long narrow folded, rolled or flat blade extending from a cylindrical leaf sheath, the layers of which help protect the immature stems and growing point. Grasses cover the ground in a variety of ways; they all produce branches known as tillers, from buds very close to the soil surface.
Some grow straight upwards, some creep across the ground sprouting new plants at intervals, and others, such as the gardener’s enemy couch grass, have underground stems (rhizomes) which are almost impossible to remove completely.
Where grasses are found
Grasses are found throughout the world, from the southernmost tip of South America to the northern reaches of Norway and Russia.
Covering a third of the world’s land, grasslands (including prairies, veldt, steppes, savanna and pampa) develop in the zone between forest and desert. The rainfall is too low for forest trees to grow, but there is still enough rain for herbaceous plants.
Did you know?
- Grass leaves grow from an area just above the ligule - if the tips are grazed or cut, the blade will continue to grow.
There are many herbaceous forest-floor species, especially in the New World, but with their woody arboreal habit, bamboos are the only grasses that can actually form forests.
In prehistoric times, people began to harvest grass seeds for food and to gather bundles of grass to construct shelters. Since then, these plants have been used in clothes and containers, in gardens and sports grounds, and even to make explosives and jewellery.
Kew's work with grasses
Kew undertakes a great deal of research into grasses, with seeds, offsets and leaf material being dispatched to botanic gardens, universities and research institutions across the world.
Where to see grasses at Kew
Kew’s Grass Garden grows over 550 species of grasses. The best times to visit are early summer for the annual grasses and cereals, and autumn and winter for the perennial grasses when these have produced their seedheads. The Grass Garden safeguards a British grass that is extinct in the wild - interrupted brome has not been seen in its native habitat since 1963.
Most of Kew’s bamboo collection can be seen in the Bamboo Garden.
Behind the scenes, there are even more grasses, with over 350,000 preserved specimens from around the world filed in Kew’s Herbarium.
Explore our species profiles: the grass family
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