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    Why do plants grow in some places but not in others? Why does some land have so many plants growing on it, while other land has almost no plants growing on it at all?

    To grow, plants need several things. One is warmth. In very cold places almost nothing grows. Plants also need water. In very dry parts of the Earth only a few unusual plants can grow. That's why there are almost no trees or grass in dry deserts.

    Plants must also have a place to put down their roots and grow. They find it difficult to grow on hard land. The town is built (被建立) on hard land. The plants there have only the soil between the cracks of the stones to grow in.

    Another thing plants must have before they can grow is food. What will happen if we try to make things grow on the sandy beach? A few plants, such as grass, will grow in sand, but most plants won't. Even if the weather is warm enough and we water the plants each day, many of them will die because the sand on this beach has almost no food for plants.