Introduction

Urban horticulture is plants for cities – functional uses of plants to improve urban environments for the benefit of the people who live there. Functional uses mean screens against unpleasant views and against headlights. It means essential food and special nutrition in the human diet – fruit and vegetable production in cities is important. It means effects upon noise and air pollution and on the amelioration of climates in urban areas. It also means plants to improve the human psyche – plants and gardens are good for people.

Why should we talk about plants in cities? Because most of us live in cities and as world populations expand, more and more people are gathered in tighter and tighter clusters. It includes us all. We get most of our information about city plants from observations and anecdotes, from nurserymen, from landscape architects, and from people who manage properties in the city. For example, the civil engineer in the city knows more about root growth of tree species than does a research scientist because he has to repair the clogged sewer lines and broken pavement caused by urban trees.

Our most substantive information comes from agriculture and forestry. And although the principles of plant growth can be demonstrated equally well with an apple tree, a Douglas fir, or a chrysanthemum, strategies developed from these plants don't apply well when we try to manage rhododendrons in gardens and parks, or a grouping of sweetgum trees along a city street, or the collection of common plants in a backyard, or the rushes and cattails of an urban wetland. Indeed, the whole concept of commercial agriculture is different from urban horticulture.