How Do Nurseries Handle Invasive Plants?

ELA recently posed a few questions to regional nurseries to find out how they learning about and controlling distribution of known invasive plants and those plants that might become invasive.

ELA: Climate change has pushed hardiness zones north in many areas and some plants that formerly died over winter now might survive and thrive. Which popular plants do you no longer sell because changes in plant hardiness zones have led to them becoming invasive?

Pat Bigelow, Bigelow Nurseries, Northboro, MA: Over the past few years, winters have not been consistently warmer for us to reliably recommend or identify any plants not previously hardy in Central Massachusetts.

Steve Castorani, North Creek Nurseries, Landenberg, PA: North Creek has not dropped plants we offer based on the question you presented. A couple years ago, we had a zone 6 winter that reset the clock so to speak. Since 80% of our offerings are native species or cultivars of such, we have not noticed invasive tendencies with any of our offering. Also, we trial our plants for invasiveness ahead of any introduction or offering.

North Creek adopted a set of New Plant Principals many years ago that are the foundation of our process. “In our never-ending quest to innovate, bring to market great new plants and offer the best value to our customers we start with the following principles:

  1. Our plants are excellent garden and or landscape performers in the mid-Atlantic region.
  2. They are not invasive or overly aggressive.
  3. Once established in an appropriate site they require no material input to maintain their ornamental value or garden worthiness.”

Peter van Berkum, Van Berkum Nursery, Deerfield, NH:  None in the past few years.

ELA: Have your sales practices changed for species that might show invasive tendencies? How do you manage out-of-state sales?

Bigelow: Having been involved since the late nineties with the scientific identification of invasive plants and the regulatory actions that followed as a charter member of the Massachusetts Invasive Plant Advisory Group, we have taken a strong and enthusiastic educational role internally with our sales force and both the nursery industry and public.  We do not sell ANY plants that are identified as invasive by MIPAG ANYWHERE!  We also specialize in growing native plants and regularly encourage their use as alternatives to invasive thugs.  We are recognized for our extensive native plant palette and knowledge of same.

Castorani: Again, we don’t feel that plants we offer have invasive tendencies. When we sell out of state it is the responsibility of the customer to manage their offerings. Over twenty-five years ago, we made a philosophic decision to not offer plants that posed a threat to the natural environment. Miscanthus grass would be one genus that fits that description, as these plants were popular then as they are now. We decided not to offer them because we were aware of their potential to become invasive.  We proactively and consciously made that decision.

Van Berkum: We have lists of restricted plants in each of the states we sell too, so we know which not to ship.

ELA: Are you involved with your state’s invasive plant advisory group? What is being done at the state level to address invasive plants? Are you provided with regular updates on invasives in your state? What about updates from surrounding states, if you sale outside your own state.

Bigelow: As company president, I am a charter and ongoing member of the Massachusetts Invasive Plant Advisory Group (MIPAG) and very much involved with the invasive plant issue at both the state and regional level.  As a member of the group, we regularly receive state and regional information and alerts and continue to help educate our industry and the public. We also regularly interact with many environmental entities regarding this issue, and attend MIPAG meetings.

Castorani: I was a founding member of the Delaware Invasive Species Council (DISC). I participated in how Delaware would address potentially invasive plant species. I was the only representative of the nursery industry among government, university and not for profit participants.  That was in 1999. I have stayed current with what has been proposed and considered by Delaware. Delaware decided to begin an education campaign rather that legislate. The biggest issue is enforcement and how the state would handle it. They decided to take a market approach and start by trying to reduce consumer demand and to suggest alternatives to invasive and potentially invasive species.  Pennsylvania is not as proactive and they lag behind other states in addressing the issue.

Van Berkum: In our state, I believe the advisory board is inactive, after having made initial list of banned plants. So we have no involvement.

ELA: Looking ahead in time, which currently popular plants might be added to the invasive species list in the next two to five years?

Bigelow: As strong supporters of science based information and decisions, I would hesitate to speculate, without facts, on which plants might be added to the Massachusetts Invasive Plant List, which includes an inclusive list of of plants found to be invasive. As an active member of MIPAG we are also part of the ongoing process to review data on plants.”

Castorani: The biggest offender that should be added is Bradford Pear. This is one plant that should be outlawed and eradicated from landscapes and roadsides. To contain invasive species, efforts need to be made to not only ban sales but to find ways to have the plants removed and remediated from existing landscapes. Non-sterile forms of Miscanthus, Barberry, Euonymus alathus, and Buddleia are just a few other species that need to be on the list.

Van Berkum: We dropped a number of plants earlier that are not banned but that we worried about, including Iris pseudacarus, Petasites japonicas, Aegopodium podagraria, Houytonia cordatum.

We are keeping an eye on Lamiastrum, but so far have not seen signs of invasiveness. Also, I have heard talk about Miscanthus being invasive, but in NH it is absolutely not, from all of our observation.

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