Invasive Species Double-edged Sword for Nurseries

The nursery industry has a love-hate relationship with invasive species regulations. On the one hand, exotic diseases like Phytophthora ramorum, a.k.a. sudden oak death, threaten the industry with direct losses through disease infections and, more importantly, indirect losses through restrictions and lost markets from quarantines imposed by other countries and states. As you’d expect, the nursery industry is a big supporter of keeping all sorts of harmful pests, plant diseases, and weeds out of Oregon.

They even tax themselves to support an emergency fund to address pest and disease emergencies that might impact their industry. This fund was tapped recently to help eradicate an infestation of Japanese beetles at Portland International Airport.

On the other hand, some plants introduced via the nursery trade have become noxious weeds, so the industry is also part of the problem. English ivy that drapes many of the trees in our natural areas is a well known example. The yellow flowers of Scotch broom that are appearing now along roadsides are another reminder. Both were introduced and sold for decades as ornamental plants. Understandably, the industry is concerned about what plants are added to prohibited plant lists and noxious weed quarantines. Today English ivy and Scotch broom have been phased out of the nursery trade. It is illegal to import, propagate, or sell them in Oregon.

Fifteen years ago when we first approached the Oregon Association of Nurseries (OAN) about banning sales of English ivy, the Executive Director told me, “That will never happen!” He told me one well-known nursery owner had “put his kids through college on sales of English ivy.” Since then the nursery industry has seen the writing on the wall, and OAN has supported recent additions of problem feral ornamentals to the noxious weed list. It is no surprise that a vocal minority still objects and thinks government should keep its nose out of what plants people can buy.

The Department started phasing out butterfly bush in 2008. A decade ago, land managers began to notice butterfly bush thriving on river banks, roadsides, and forest clearcuts. It showed all the signs of becoming as weedy as Scotch broom. After the State Weed Board added it to the official list of noxious weeds, I reluctantly cut down the three bushes in my yard. I love butterflies, so it was not something I wanted to do. However, this story is going to have a happy ending. The nursery industry responded to our regulations by developing new seedless hybrid varieties, analogous to seedless grapes or seedless watermelons. We adopted a 98% reduced fertility requirement and set up a process for independent review of fertility trials through Oregon State University. A dozen new seedless varieties have been approved in the past few months. They just began to trickle down to garden centers and catalogs. These complex inter-specific hybrids can’t revert to the wild type, and they produce little, if any, viable seed.

I’m holding a couple of spots in my yard for them. In reviewing the approval paperwork, I’ve seen pictures from the trials, and the plants are spectacular. They are compact, have more flowers, and have longer blooming periods than the older seeded varieties, and they still attract butterflies!

This is a big deal, and not just for me. It is the first time plant breeders have considered and successfully addressed invasiveness in developing new ornamental varieties. Oregon is leading the way. Regulators and plant breeders all over the country are watching us. Hopefully this is just the beginning. Oregon State University has recently hired a young plant breeder, Dr. Ryan Contraras, to develop new ornamental varieties. I toured his lab, greenhouse, and field plots last week. He’s started work on a dozen different types of plants—from Norway maple to ornamental grasses. In several cases, sterility to prevent invasiveness is a primary goal of the breeding.

If it ever warms up this spring and you get a chance to visit your local garden store, you’ll see a large variety of plants. You shouldn’t miss the few bad apples that have been phased out. While you’re there, if you see any of the new seedless butterfly bush varieties, like Blue Chip, White Icing, or Peach Cobbler, and are seduced into buying some by the gorgeous pictures on the label, remember. . . save some for me!   

Dan Hilburn