In many areas of California, winter temperatures can pose a threat to the fruit and foliage of citrus and other subtropical trees such as avocado (Persea americana), loquat (Eriobotrya japonica), guava (Psidium spp.), and macadamia (Macadamia spp.). Susceptibility to frost depends on the health and vigor of the plants, the characteristics of individual species or cultivars, the rootstock on which the individual trees are grown, and the intensity and duration of the cold.