I hear people talking about various plants and saying it’s a bad plant because it’s invasive. What does this mean and what are some invasive plants I should look out for? TL

Invasive plants are a problem and Oklahoma has some that cause us concern, but the term invasive oftentimes gets used inappropriately. By inappropriately, I mean that some people use it to describe plants that spread. Most of the time we like plants that grow and expand their territory. It’s in this way that a single coneflower can expand to fill in blank spots in your garden, but that doesn’t mean it’s invasive.

According to the USDA an invasive plant is “a plant that is both non-native and able to establish on many sites, grow quickly, and spread to the point of disrupting plant communities or ecosystems.” By non-native they mean plants that are not naturally found in a particular area and unfortunately, most invasive species of plants are plants that gardeners have unknowingly purchased and brought home to their gardens. We all like something new and interesting, but sometimes that comes back around to bite us.

Perhaps one of the best-known examples of an invasive plant is the Bradford pear. The Bradford pear is a hybrid that was originally bred to be a sterile, thornless ornamental pear that would be resistant to fire-blight. Unfortunately, they easily cross-pollinate and produce small, 1/2” fruits. When it freezes in the fall, these fruits become soft, the birds eat the small fruits, and then the seeds get spread in the bird droppings.

The trees that sprout from these seeds have reverted to their Callery Pear origins which had thorns and tend to grow into thick stands, displacing naturally occurring plants. Your best bet to get rid of a Callery Pear is to cut it down and treat the stump with a product containing triclopyr.

Alternatives to planting a Bradford Pear would include Eastern redbud (Cercis canadensis), American plum (Prunus americana), Mexican plum (Prunus mexicana), and Carolina buckthorn (Frangula caroliniana).

Kudzu in another invasive plant that is beginning to have an impact here in Oklahoma. Kudzu was introduced int 1876 at the Centennial Expo in Philadelphia as an ornamental plant. It was later used to help control soil erosion. Unfortunately, it is now considered one of the World’s Worst Top 100 Invasive Plants. The problem with Kudzu is that it grows quite quickly and creates a very dense growth that then completely covers existing plants and even structures. When I say rapid growth, I’m talking 18 inches per day. Kudzu requires removal and/or treatment with herbicides for complete elimination.

Another one considered invasive is Bermudagrass. Yes, I know many of us have bermuda lawns and really like it, but out in the field it is an issue for farmers as it can compete with crops for water and nutrients. In farm or garden situations, black plastic mulch or garden cloth can help limit bermuda’s ability to spread into your garden.

For more info on invasive species, what you can do about them, and alternative plants to consider, go to the Hot Topics section of our website. Good luck!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo: OSU Agricultural Communications Services