Invasive species create negative habitat problems

Queen's Wreath spreads atop tree branches. (Photo by Anita Westervelt)

Published in the McAllen Monitor, January 17, 2026

Story and photos by Anita Westervelt

Texas Parks and Wildlife Department and Texas A&M AgriLife Extension Service, who sponsor the statewide Texas Master Naturalist program, encourage Texans to learn more about invasive species.

Volunteer organizations like Texas Master Naturalist, Native Plant Project, Native Plant Society of Texas, and local city, county, state and national parks provide events and lectures to help promote public awareness about invasive species.

Another way to learn about invasive species is through a community-involved citizen scientist bioblitz, like the one scheduled for January 24 and 25. Sponsored by the Native Plant Society of Texas to document invasive plants using iNaturalist.org, residents may join the bioblitz at https://www.inaturalist.org/projects/2026-npsot-invasive-species-bioblitz or by searching the projects in iNaturalist.org for “2026 NPSOT Invasive Species BioBlitz.”

Invasive plants have some common negative traits. They are capable of producing huge amounts of seed, thrive in their nonnative environment and outcompete native species for sunlight, water, nutrients and space. An invasive plant can alter soil chemistry and inhibit native plants from growing, alter or destroy biodiversity and create negative impacts on wildlife.

An Internet search of “South Texas Plains Texas Invasives” brings up a list of invasive plants particularly worrisome in the Rio Grande Valley. The website, Texasinvasives.org, offers information about Texas’ invasive species. It also has an Invasives Database where plants can be looked up by common or scientific name to find if they are listed as invasive in Texas. A valuable resource to check before purchasing new plants for a garden or landscape.

Five of the invasive species that significantly plague the Rio Grande Valley are described below:

Giant reed, Arundo donax. Native to India. Canes are highly flammable. They can grow to 30 feet tall; leaves grow like corn stalks; feathery plumes top the foliage. Plants spread from thick rhizomes; root masses can cover several acres. Cut, even long-dried stems touching the ground sprout roots. Giant reed sucks water from its surrounds, displaces native vegetation and leads to significant plant, fish and wildlife biodiversity loss. It chokes rivers and resacas, alters hydrology and interferes with flood control.

Giant Reed knows no boundaries. (Photo by Anita Westervelt)

 Common water hyacinth, Pontederia crassipes. Native to the Amazon River basin in South America is invasive in more than 50 countries. Free-floating water plants rapidly reproduce. Thick mats of common water hyacinth blanket the Rio Grande under Progresso International Bridge and local resacas. Plants can get three feet tall. Long dark roots reproduce via fragmentation, forming impenetrable mats that clog waterways and shade submerged native plants, which often die; resulting decay processes deplete dissolved oxygen in the water and lead to fish kills.

Common Water Hyacinth blooms are beautiful; the plant is highly invasive. (Photo by Anita Westervelt)

Common Water Hyacinth blanketing a resaca. (Photo by Anita Westervelt)

Queen’s wreath, also called corona de reina and coral vine, Antigonon leptopus, (top photo) is native to Mexico’s Pacific and Atlantic coastal plains and to South America. A deciduous, fast-growing vine that climbs by tendrils to 40 feet. Three-inch heart-shaped leaves are textured looking. Cascading clusters of hot pink or white flowers bloom profusely along the vine, subsequently producing huge amounts of viable seeds. Animals and birds eat fruit and seeds and help spread the plant. Vines climb to the top of trees, seeking sun, eventually killing what it smothers.

Castor bean, Ricinus communis. Native to tropical east Africa around Ethiopia. Plants can grow 20 feet tall with a single thick, tough stem at the ground and numerous ascending branches above. Leaves can reach 23 inches across. Blooms have showy pink stigmas and yellow anthers; pollen is toxic to honeybees. A heavy seed producer, seeds can remain viable for three years. Leaves and especially seeds contain a powerful toxic enzyme called ricin; it is toxic to humans, cattle, horses, rabbits, pigs, goats, cats, dogs and poultry. Plants exhaust soil and deposit high ricin concentration from seed and leaves.

Castor Bean flowers and leaves are attractive; plants are not good for the habitat. (Photo by Anita Westervelt)

Tall Castor Bean plant among Black Willow trees along a resaca bank. (Photo by Anita Westervelt)

Saltcedar, Tamarix ramosissima. Introduced from Eurasia in the 1800s for ornamental landscaping. Blooms attract insects but trees are not attractive to bird activity. Trees can grow 20 feet tall. They are aggressive reproducers, consume large amounts of water and produce thousands of seeds annually. Leaves and stems secrete high concentrations of salt into the ground, preventing native plant growth. Saltcedar can grow in high salinity, drought conditions and submerged. They replace native vegetation, reduce biodiversity and degrade wildlife habitat.

Pretty pink Saltcedar blooms and feathery foliage. (Photo by Anita Westervelt)

There are 179 nonnative plants considered invasive in the Texas invasives database, both aquatic and land. Different state agencies and organizations maintain different lists based on ecological, regulatory and economic threats. Plants, vines, shrubs or trees, beautiful in their own right, may be harmful to our natural habitat, making it wise to be careful what we introduce into our own gardens.

For a list of local nurseries that carry native plants, visit: https://www.stbctmn.org/post/valley-native-plant-growers-nurseries

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