In fact, the answer is growing under your feet. Even in these days of timber decking, 80 per cent of Britain's gardens include an area of lawn. Given that the average size of a British garden is 2,000 square feet, and that the average lawn accounts for half that area, we have an awful lot of grass in our green and pleasant land.
But then grass of one sort or another constitutes the greater part of the Earth's vegetation. Which is maybe why we have simply stopped noticing it. Yet without it, we wouldn't be here. The seeds of grasses such as wheat, barley, oats, rice, millet and maize provide us with much of our food, while the animals we depend on eat the leaves of grass for a living. Bamboo is a grass, and so too are all those reeds and rushes. Even sugar cane comes from a grass.
In its wild forms, grass grows everywhere, from the savannah to the poles. Among the 6,000 species worldwide are even some that grow in the sea and on river beds. Many of the larger grasses have become familiar as ornamental garden plants.
But it's that low-growing, carpeting plant that most of us think of when we talk about grass - even if we have no idea which particular variety we mean. For the most homogeneous-looking lawn is likely to me made up of several grasses, each with it own characteristics. Buy a packet of seed for the garden and you'll probably get a blend containing fescues and bright green meadow grasses. A football pitch, on the other hand, will contain hard-wearing rye grass.
It was the British who invented the lawn in its modern form, but it is the Americans who have made its upkeep a national obsession, with a lawn-care industry worth $300 billion (pound;213.7 billion). The grass, it seems, is even greener on the other side.