Privets are any of a number of shrubs or trees in the genus Ligustrum, many of which are invasive. The genus contains about 50 species native to the Old World and Australasia. Many members of the genus are grown as ornamental plants in parts of the world. Several species of privet have become a nuisance in regions outside their ranges. In these conditions they are most commonly found wherever there is disturbed soil, soil that is physically perturbed from its natural state through fire or mechanical machinery, such as along fencerows, old fields, ditches, and forest margins. Privet grows particularly well in riparian forests, which are found throughout the Southeastern United States. Although tolerant of varying soil and light conditions, including a tolerance for shade, privet survives best in mesic soil with abundant sunlight. Economic and cultural effects Privet is considered a huge problem in New Zealand and the east coast of Australia (Ligustrum lucidum, Ligustrum sinense and Ligustrum vulgare). It is banned from sale or cultivation in New Zealand because its pollen is known to cause asthma and eczema in sufferers. Privet can be removed by contacting local government agencies to report its presence. but in Auckland it is only a surveillance pest plant in the 2012 Regional Pest Management Strategy. The NZ Weedbusters site provides guidance on how to get rid of the plant. When privet is invasive species, the cost of controlling and removing privet is economically detrimental, something that is problematic for conservation efforts. The annual cost of removing Chinese privet in the United States is estimated to be $737 per acre when a mulching machine and two-person herbicide application crew are employed. The cost for foliar glyphosate applications on privet is approximately $130 per acre for chemical and surfactant treatments. Invasiveness Privet is a successful invasive species because of its ability to outcompete and therefore displace native vegetation. This competitive superiority to native vegetation is connected with the plant's ability to adapt to different light conditions. For example, in low light environments, privet is able to produce fewer and larger ramets than its competitors. These larger ramets make privet more tree-like, making privet better able to compete for light than its more shrub-like native counterparts. Privet is an ideal invasive species because it reproduces both sexually and asexually. Through sexual reproduction, privet produces seeds that are easily dispersed by wind and animals. These seeds can