As gardeners, we may consider ourselves stewards — of plants, of the land, of beauty. One of the biggest threats to the natural Oklahoma landscape is invasive plants. While that might seem like a problem reserved for park rangers and the like, these weeds could be masquerading as specimens in your own garden, and many are still sold in nurseries and big box stores. But why worry about them at all? Invasive plants in Oklahoma not only are detrimental to native plants and wildlife but also clog waterways, impact agriculture, and require significant economic input to remove.
Invasive Plants in Oklahoma
The following is a list of some of the worst invasive plants likely to be found in Oklahoma gardens. If you see one in your own yard, look up your local Extension office for information on how to get rid of it properly. And if you notice an invasive plant for sale, kindly ask the seller to stop offering it — they might not know it’s problematic. Although a similar nonnative but harmless plant could be grown in place of an invasive species, choosing a native alternative will have a decidedly positive impact. Each invasive plant description includes a couple suggestions for similar native plants.
1. Chinese privet (Ligustrum sinense)
A popular ornamental shrub introduced from China in 1852, Chinese privet is medium-sized and semi-evergreen. It reproduces quickly via root suckers as well as seeds dispersed by birds. Its small, opposite leaves are shiny, dark green, and ovate. In late spring, it produces small panicles of white, malodorous flowers, and the berry-like drupes that follow mature to purple-black.
Alternative native shrubs include coralberry (Symphoricarpos orbiculatus), which is deciduous, and yaupon holly (Ilex vomitoria), a similar evergreen shrub with white flowers and bright red berries.
2. Chinese and Japanese wisteria (Wisteria sinensis, W. floribunda)
Chinese and Japanese wisteria are long-lived, woody vines that twine tightly around tree trunks, often damaging or killing the trees. New vines both grow from seed and sprout from rootstock. In spring, they produce the large, showy, dangling panicles of pink to purple flowers for which they are known. Velvety seed pods ripen in fall. One notable difference between the two species is Chinese wisteria twines counterclockwise and Japanese wisteria clockwise.
Also very similar is American wisteria (W. frutescens), which makes a perfect alternative, or choose another native vine, such as trumpet creeper (Campsis radicans).
3. Eastern redcedar (Juniperus virginiana)
Although it doesn’t happen often, sometimes a native plant becomes invasive. Such is the case with eastern redcedar, a medium-sized evergreen whose population has gotten out of control due to fire suppression and overenthusiastic ornamental and windbreak plantings. Actually a juniper, not a cedar, it has blue-green, scale-like leaves and reddish, peeling bark. Female trees produce blue berry-like cones, and males produce pollen-bearing cones.
Shortleaf pine (Pinus echinata) makes a good native alternative evergreen tree, and Rocky Mountain juniper (J. scopulorum) shares the same genus.
4. Hydrilla (Hydrilla verticillata)
Hydrilla is an aquatic plant with stems that rise to the surface, shading out native plants, causing stagnant water, and crowding out waterfowl. It tolerates many challenges and spreads via rhizomes, tubers, stem fragments, and aboveground stolons. The slender, branched stems grow up to 25 feet long. Small, narrow, sharply serrated leaves grow in whorls, giving the plant a bottlebrush appearance. Tiny, white, six-petaled flowers bloom late summer into fall.
Native aquatic plants to grow instead include coontail (Ceratophyllum demersum) and waterweed (Elodea canadensis or E. nuttallii).
5. Japanese honeysuckle (Lonicera japonica)
A deciduous to semi-evergreen climbing vine, Japanese honeysuckle can smother shrubs and small trees as well as form dense ground cover. It spreads aggressively via rhizomes, seeds, and runners that root wherever their nodes touch soil. It has opposite, ovate, dark green leaves and hollow stems when mature and blooms throughout summer with white to yellow, sweetly fragranced tubular flowers. Its berries ripen from green to red to blue-black.
Yellow honeysuckle (L. flava) is a native vine from the same genus, while passionflower (Passiflora incarnata) is another beautiful native flowering vine.
6. Mimosa (Albizia julibrissin)
A showy but unfortunately problematic deciduous tree, mimosa produces unique fringed, pink blooms in the summer, for which it is also called silktree. Large, feathery, bipinnately compound leaves provide an attractive backdrop. It resprouts as well as spreads via seed dispersal. This small to medium tree has a broad crown and averages 10 to 50 feet tall.
Plant a native sumac (Rhus spp.), with its compound leaves and showy flower panicles, or lovely American fringetree (Chionanthus virginicus) instead.
7. Saltcedar (Tamarix spp.)
Several species of saltcedar were introduced to the US as ornamentals in the early 1800s but unfortunately escaped cultivation and became invasive throughout much of the country. This shrub to small tree readily resprouts to form colonies and is a prolific seed producer. It has slender stems with scale-like leaves resembling those of a cedar or juniper. In summer, it produces feathery racemes of white to pink flowers.
False indigo (Amorpha fruticosa) has a similar appearance with airy, pinnately compound leaves and dense spikes of unique deep purple flowers. Buttonbush (Cephalanthus occidentalis) is another lovely native shrub with unique white, spherical flower clusters.
8. Siberian elm (Ulmus pumila)
A medium-sized deciduous tree, Siberian elm is extremely adaptable, hardy, and fast-growing and often forms dense thickets. It has dark green, doubly serrate leaves with an ovate to lanceolate shape, and one side is often larger than the other. Drooping clusters of non-showy light green to reddish flowers bloom before the leaves appear, and the fruits are winged samaras. Reddish-brown to black buds are present in winter.
Plant American elm (U. americana) or hackberry (Celtis laevigata) instead.
9. Yellow bluestem (Bothriochloa ischaemum)
An allelopathic perennial grass, yellow bluestem not only crowds out native plants but also inhibits their growth. It has rhizomatic growth and an erect habit, though older stands often form a sod. Its yellow-green leaves may be flat or folded, and it closely resembles native bluestem grasses except when flowering: look for reddish-purple, fan-shaped, finger-like panicles.
Though belonging to a different genus, little bluestem (Schizachyrium scoparium) resembles yellow bluestem. Side-oats grama (Bouteloua curtipendula) also makes a nice alternative native grass.
Let’s all be gardeners who make a positive impact on the places we live. Keep an eye out for invasive plants on your property (and where plants are sold!), and if you find one, take the time to remove it and then do the fun work of searching for a beautiful native alternative to plant.
Plant These Oklahoma Native Plants For A Low Maintenance Landscape
Replace any invasive plants you find around your property with one or more of these native plants and you’ll have much less maintenance to worry about, since natives help control soil erosion, reduce air pollution, and are less fussy.
Check out our Oklahoma native plants list to help you decide the best plants to use in your garden or landscape.