Pennsylvania's Invasive Plant List – How it Works

In the past several years, we have spread the news that several once-popular landscape plants were added to the Pennsylvania Controlled Plant and Noxious Weed List.  According to Pennsylvania law, a noxious weed is "a plant that is determined to be injurious to public health, crops, livestock, agricultural land, or other property." Most plants on the noxious weed list are recognized nuisances (for example, Canada thistle, poison hemlock, and stiltgrass). Some, such as Japanese barberry, Callery (Bradford) pear trees, privet, and burning bush were once popular landscape plants and still grow in many landscapes, but these plants have been found to be invasive. Their placement on the noxious weed list is part of a long-term plan to lessen their impact on the environment. When a plant is placed on the list, plant sellers have a grace period to stop selling the plant, but eventually, the propagation and sale of the banned plant in Pennsylvania becomes illegal.

History of the Noxious Weed List 

Pennsylvania Department of Agriculture (PDA) controls the administration of the Pennsylvania Controlled Plant and Noxious Weed List and its website outlines the history and process very clearly. To summarize, the first noxious weed law in Pennsylvania was enacted in 1862 to control Canada thistle, chicory, Johnsongrass, and "marihuana." (Chicory no longer appears on the list.) In 2017, the law was expanded and codified into a list of three categories: 

• Plants that are established in Pennsylvania and are intended to be eradicated.
• Plants that are widely established in Pennsylvania and cannot feasibly be eradicated.
• Plants currently on the Federal Noxious Weed List that are not currently in Pennsylvania, but would pose a threat if introduced. 

How is the Noxious Weed List administered?

The 2017 law created a committee to oversee the Pennsylvania Controlled Plant and Noxious Weed List. This committee decides on the addition and deletion of plants. According to PDA's website, it is comprised of the secretaries of various state committees, the chairperson and minority chairperson of the Agricultural and Rural Affairs Committee of the PA Senate and House of Representatives, and Pennsylvania citizens who represent agriculture, the green industry, and an institution of higher learning. The committee meets quarterly and the meetings are open to the public. For details on the committee structure and meeting schedule, visit PDA’s Controlled Plant and Noxious Weed Committee.

What about sterile versions of banned plants? 

A nursery or plant breeder cannot simply begin selling a sterile plant—one that cannot reproduce and therefore would not naturalize in the environment. Sterile cultivars of plants on the Noxious Weed List must be approved through an application to PDA. To date, four cultivars of Japanese barberry (Berberis thunbergii) have been approved: the WorryFree® Series of barberries from the company SynRG, LLC. One cultivar of glossy buckthorn (Frangula alnus) has been approved—Rhamnus 'Fine Line'.

What plants are of concern and being considered for addition to the Noxious Weed list? 

According to Trilby Libhart, Botany & Weed Specialist, Pennsylvania Department of Agriculture, Imperata cylindrica 'Red Baron' is under discussion for inclusion on the list. Commonly known as Japanese blood grass, it is available in the nursery trade as an ornamental plant. However, it is reputed to lose its attractive red color and become invasive when grown in shade. If you have a concern about a plant, you may email RA-plant@pa.gov with the subject line: Controlled Plant and Noxious Weed List Request.