Monoculture means the use of land for growing only one type of plant, or the plant culture that results from such use. This practice has the effect on a landscape or agricultural crop that is the opposite of biodiversity, and it can sometimes be responsible for the spread of plant diseases.
The planting of bedding plants en masse (sometimes forming a monoculture) is a widely encountered phenomenon in landscaping. Since these, however, are typically annual plants, there is less concern over disease because the investment in plant material is less than for perennials.
Sometimes the development of a monoculture is unintentional, as when an invasive plant such as Japanese knotweed crowds out all competition and dominates an area of the landscape.