Taming Invasive Species

It is welcome news that lawmakers and the public now recognize the threat of certain exotic species which can displace our native species and alter our native ecosystems. Gardeners, nurserymen, landscaper architects and other land stewards need to act responsively to preserve our native habitats. No one wants to be responsible for the next purple loosestrife, kudzu, or multiflora rose, all well known examples of problematic species. The proverbial Pandora’s box has been opened, and now the question is how to close it.

Lawmakers have been scrambling to solve the problem of invasive plants. Banning plants “deemed invasive” has been the main tool utilized thus far. For example, the Ohio Department of Agriculture has just banned 38 plant species of plants. Banning these weedy, seedy plants should please environmentalists and gardeners alike because most have no commercial or ornamental value. But how do we address address plants that do have horticultural value? 

Plant scientists, horticulturists, farmers and gardeners have been breeding and selecting cultivars since the dawn of agriculture. Historically, cultivars have been developed to produce greater crop yields, larger fruit and bigger, more colorful flowers. But they have also developed breeding techniques to create seedless plants. We're all familiar seedless oranges, seedless watermelons and seedless bananas. So why not create seedless ornamental plants to solve the invasive plant problems? Researcher are!   

North Carolina State University researcher have been at the forefront of taming invasive species. Dr. Dennis Werner developed the Lo & Behold® series of butterfly bush (Buddleia) which was granted an exemption in Oregon where Buddleia has been banned because of its evasiveness in the Pacific Northwest.    

Black Knight butterfly bush (left) and Lo & Behold Purple Haze (right) 

Dr. Thomas Ranney, another plant researcher at NSCU, has developed two seedless cultivars of Japanese barberry (Berberis thunbergii). One of the cultivars, Sunjoy® Mini Maroon produces fruit, but just like navel oranges the fruit contains no seed. Sunjoy® Toto, another dwarf, dark leafed selection does not produce any fruit at all. Both Sunjoy® Mini Maroon and Sunjoy® Toto perfect replacements for the purple cultivars of  barberry that have been shown to be invasive in the Northeastern United States.

The fruit of Sunjoy® Mini Maroon barberry contains no seed rendering it non invasive.

Sunjoy® Mini Maroon - the environmentally friendly barberry. 

Comparison of female fertility traits among cultivars of Berberis.
Fruit Set (%)
Germination (%)
fertilityZ (%)
 0.3 B
0.10 B
 0.0 B
 0.0 B
 0.0 B
Sunjoy Toto ‘NCBX1’
 0.0 B
0.00 B
 0.0 B
 0.0 B
 0.0 B
‘Golden Devine’
 33.8 A
1.15 A
 38.3 A
 0.16 A
 71.3 A
 42.7 A
1.26 A
 41.1 A
 0.22 A
 100.0 A
37.4 B
 0.09 B
23.3 B
0.003 B
 1.2 B
 66.0 A
 1.30 A
 30.3 B
 0.284 A
 100.0 A
 33.5 B
 1.13 A
 56.4 A
 0.220 A
 77.6 A
ZRelative fertility = seedlings/flower of that cultivar divided by seedlings/flower for the highest cultivar measured that year x 100.  Means followed by the same letter, within a column, for a given year, are not significantly different, P<0 .05="" a="" anova="" based="" font="" means="" on="" separation.="" waller-duncan=""> 
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Cultivars such as these have the potential to, in part, solve the invasive plant problem, but in some cases states are banning them along with the culprit species. It’s frustrating because plant breeders are addressing this issue and their work is going to waste because people are simply uneducated. Legislators are throwing the baby out with the bathwater. 

At the moment few people seem to care about the cultivar issue because they don’t know that environmentally safe, seedless cultivars exist. Gardeners, like environmentalists, are proud of our natural heritage and want to preserve native habitats. They want to do what is morally right, but they also want to create beautiful gardens in our man made habitats. Cities and suburbs present challenging growing environments and some plants perform better than our native plants. 

There are others who do know about non-invasive cultivars and are content to keep quiet because they’re not gardeners and they don’t want to complicate the invasive plant issue. Their goal is to keep the process moving. And the process is moving fast. The question is “will gardening public wake up and smell the roses?” Perhaps, but it may be too late to make a difference, as states continue to ban environmentally friendly cultivars.

Gardeners and growers are not the bad guys and they need not be the losers. Non-invasive, seedless cultivars are the answer and not the problem in the complex issue of invasive species.