Identifying Invasive Oklahoma Plants

As defined by the U.S. Forestry Service, invasive species are “non-native (exotic/alien) to the ecosystem that they occupy, and their existence in that ecosystem causes or is likely to cause harm to the economy, environment or human health.” Can you tell the difference?

Why is it important to know which plants are invasive in Oklahoma? Also, how can you tell the difference between an invasive species and one that is simply aggressive?

As defined by the U.S. Forestry Service, invasive species are “non-native (exotic/alien) to the ecosystem that they occupy, and their existence in that ecosystem causes or is likely to cause harm to the economy, environment or human health.”

That’s complicated, so I spoke to Julia Laughlin, Oklahoma County Extension horticulture educator, and she had a simple yet effective definition for invasive plants. “An aggressive plant might be a problem in your garden depending upon your soil type and microclimate, while an invasive plant becomes a problem for those around you and in the environment.”

Invasive plants crowd out native plants in an ecosystem, which is a huge issue. Some like Eastern redcedar, Juniperus virginiana, are also a wildfire hazard in our state.

Invasive water plants like yellow iris, Iris pseudacorus, can also clog waterways and crowd out native water plants.

“One of the best things you can do is take a good look around, see what you like and research it before you buy. Also, you can call your county extension office if you have questions,” Laughlin says.

Start with Oklahoma’s Dirty Dozen plant list compiled by the Oklahoma Invasive Plant Council. The plants listed are:

• Cheatgrass – Bromus tectorum
• Chinese privet – Ligustrum sinense
• Eastern redcedar – Juniperus virginiana
• Field brome – Bromus arvensis
• Hydrilla – Hydrilla verticillata
• Japanese honeysuckle – Lonicera japonica
• Johnsongrass – Sorghum halepense
• Musk (nodding) thistle – Carduus nutans
• Russian thistle – Salsola tragus
• Saltcedar – Tamarix spp.
• Sericea lespedeza – Lespedeza cuneata
• Siberian elm – Ulmus pumila
• Yellow bluestem – Bothriochloa ischaemum

Before you take a start of a passalong plant from a friend, first note how it grows in their garden. Then, do a quick online search to make sure it isn’t considered invasive or on the Oklahoma Invasive Plant Watch List, www.okinvasives.org/watch-list-1.

If it is a problem plant, Oklahoma State University has a fact sheet for those too. Included on the problem plant list is the Callery or Bradford Pear, Pyrus calleryana, which has escaped into wooded areas throughout our state.

Plants may also be reported as invasive on U.S. public lands. Although Autumn clematis, Clematis terniflora, isn’t on the invasive lists for Oklahoma, it is a real thug in my garden popping up in places throughout my landscape. Autumn clematis is also on the invasive plant list in several Eastern states and on public lands. Perilla, Perilla frutescens, and garlic chives, Allium tuberosum, are two other plants that can be aggressive at best, and may be considered invasive in the future. I think it’s better to remove them from my garden now instead of letting them march onward.

When considering a new plant for your landscape, look for native versions instead of those introduced from other countries. An excellent example is planting American wisteria, Wisteria frutescens, instead of Chinese wisteria, W. sinensis, or Japanese wisteria, W. floribunda, although you’ll see the Asian varieties sold in some box stores usually in spring.

The longer I garden on my rural acreage, the more I realize I’m its steward. To get rid of invasive plants, I first do research and then I use whatever means needed to eradicate them. Sometimes, I must use chemical controls, but I can remove other plants manually. Most of us who have gardened awhile have at least one problem plant. I have my husband’s grandmother’s Japanese honeysuckle I’m still trying to eradicate 40 years later.