Drip irrigation is used in farms, commercial greenhouses, and residential gardens. This resulted in many more greenhouses being constructed on smaller farms and garden centers. Some species can be a nuisance in shady greenhouses or a weed in gardens. The botanical garden consists of three greenhouses with some outside space. Chlorpyrifos was never approved for use in Denmark, except on ornamental plants grown in greenhouses. Mirrors can be used to produce enhanced lighting effects in greenhouses or conservatories. Bumblebees are also reared commercially to pollinate tomatoes grown in greenhouses. An example of inoculative release occurs in the horticultural production of several crops in greenhouses. He also arranged for the construction of greenhouses and a kitchen garden. Maltodextrin is used as a horticultural insecticide both in the field and in greenhouses. Most greenhouses use sprinklers or drip lines. Water spinach is also potentially suitable for cultivation in greenhouses in more temperate regions. Moss can be a troublesome weed in containerized nursery operations and greenhouses. There is a widespread use of drip irrigation and greenhouses. Van Cortlandt Park contains Citywide Nursery, one of three greenhouses operated by NYC Parks.