The Invasive and Noxious Privet

What traits placed privet among the Department of Agriculture's noxious plants?

An acquaintance recently asked me why so many familiar landscape plants are now considered bad. A moment earlier, he complained about hairy bittercress, Cardamine hirsuta, popping up on his lawn. He didn't like those weedy white flowers among the turfgrass. So, what makes a plant "bad?"

Privet, Ligustrum spp., was purposely imported from Asia and Europe as an ornamental shrub in the mid-1800s for single and mass plantings. Privet tolerates shearing well, making it ideal for hedges and topiaries. Without pruning, privets may grow over ten feet tall. Most privet species are winter leaf-losing (deciduous) in Pennsylvania, but their leaves appear early in the spring and drop late in autumn. In areas with warm winters, some privets are evergreen. Their dense branches and small leaves make them ideal for privacy screens. The privet's root system is extensive and increases its branch density by forming suckers that broaden the plant's width. Clusters of fragrant white flowers form in early summer. Soon, these panicles become pea-sized blue-black fruits readily consumed by birds. Privets tolerate all soils, poor or fertile, moist or dry. They prefer sunny areas but tolerate shade well. Even white-tailed deer, Odocoileus virginianus, do not feed on their leaves or branches. It surely sounds like an excellent plant for the landscape! I just described the problem with privets.

Invasive plants produce copious fruits or seeds dispersed by birds or mammals, often into natural, wooded areas. Invasive plants germinate or leaf out early in the spring to shade out their competition. They thrive in any habitat.

A noxious plant is a plant that has been deemed much more than invasive by the Pennsylvania Department of Agriculture. A noxious plant is injurious to public health, crops, livestock, agricultural land, or other property and cannot be sold, transported, planted, or otherwise propagated in Pennsylvania. In the case of landscape plants, their status as noxious plants is announced a year or more before the actual ban date so that propagators can plan their inventory.

In Pennsylvania, four species of privets are listed as noxious plants, effective on January 10, 2025. Japanese privet, Ligustrum japonicum, Chinese privet, L. sinense, European privet, L. vulgare, and border privet, L. obtusifolium are listed. Despite its common name, California privet, L. ovalifolium is not native to North America. This species of privet is not listed as a noxious plant in Pennsylvania, but may be considered invasive in nearby states.

Because of the privet's properties as an invasive plant, it isn't easy to control. Small plants can be pulled by hand, but any remaining roots will likely resprout. Mowing is a temporary measure due to extensive root systems. Prescribed burning damages only the above-ground portions of privet and may cause permanent damage to nearby desirable plants. Chemical controls can be successful when properly applied. Different treatments are needed at various times of the year to be effective.

Select native shrubs instead of privets for your landscape. Consider these native shrubs: red chokeberry, Aronia arbutifolia; black chokeberry, Aronia melanocarpa; fragrant sumac, Rhus aromatica; arrowwood, Viburnum dentatum; inkberry holly, Ilex glabra; and winterberry, Ilex verticillata. Remember the shrub dogwoods: silky dogwood, Swida amomum; gray dogwood, Swida racemosa; and red twig dogwood, Swida sericea. The genus name of silky, gray, and red twig dogwoods has recently changed from Cornus to Swida.)