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Fredericksburg Chapter

Invasives

Let’s start with the immediate question.

“What are invasive plants?”   And then follow with why be concerned and what we need to  look for.

The term “invasive” describes alien species , usually native to Europe, Eurasia, or Asia. According to the National Invasive Species Information Center  “…these plants are characteristically adaptable to the climate and soil of their new habitats,” and cause harm to the environment or humans.

  • They thrive without cultivation,
  • expand into natural areas displacing the native plants,
  • disrupt naturally-balanced native ecosystems of plant, insect and wildlife,
  • and grow aggressively with a high reproductive capacity. Many have a

 

In their new location they are without the environmental checks and balances of seasonal weather, diseases, or insect pests that kept them under control in their native range. Their vigor combined with a lack of natural enemies often leads to “outbreak populations.” 

As a result invasive plants become a monoculture – crowding out the native species and impacting the ecosystem that supports the native plant foundation.  Insects native to the Edwards Plateau don’t use invasives as food, habitat, or as host plants for larvae. With the destruction of the natural ecosystem, the food supply for nesting birds and the larger, key wildlife species is undermined.

How Do Invasive Species Get Here?    There are several routes. Usually, we have something to do with it in some manner. 

  •  seeds and weeds sneak in through imported nursery plants and soils.
  • landscapers and friends misidentify/or give us unknown plants. 
  • travelers bring home fruits, flowers or seeds as souvenirs.
  • Then there are migratory birds who eat fruit there and poop out the seeds here.
  • And wind. The only control we have over birds and wind is to not provide additional resource.

 

But some species have been purposefully introduced to “improve” our natural resources.

* Russian thistle (Tumbleweed), while not included in the top dirty dozen, was introduced as a cattle feed in the midwest. Wind spreads the fine seeds as the dry plants tumble.

*The bunch grass King Ranch Bluestem (KR Bluestem) was seeded on degraded rangelands in west Texas as graze for cattle and for soil and water conservation. Wind spreads the fine seed.

*Chinaberry (Pride of India), was imported in the early 1800’s as a shade tree.   It continues to be sold widely as a popular ornamental tree. Birds spread the seeds from the berries creating monocultures. 

 

Horehound,(Marrubium vulgare L.) a native of the Mediterranean, arrived in North America with the colonists as a medicinal plant for the herb garden. (You have probably had horehound cough drops.) Its fine seeds flourish readily on disturbed ground. It grows wild now across the country.

Pyracantha spp.

 

Stewardship: What Can We Do As Consumers and Gardeners?

In 2017 the Board of Directors of the Fredericksburg chapter NPSOT  raised the issue of the degradation of the Hill Country ecosystem with a letter sent to the largest big box stores. Our goals were to help their managers,  and those in the main offices who order the plants, understand the issue, to register our concerns, and to ask them not to sell plants on the Edwards Plateau“dirty dozen” list. We can all

  •  Consider using plants from native plant nurseries.  Native plants are best suited for your microclimate and require minimal upkeep. They also help support native fish and wildlife by providing them with the sources that they consider as foof.
  • When disposing of plants with the potential of spreading, completely dry or freeze the plants to kill them. Then add them to household garbage that will not be composted. Do not dump aquatic plants into waterways.
  • Learn to identify invasive non-native plants, as well as recognizing the native plants of the region.
  • Remember! Plants from other regions of the world are houseguests.  Help them mind their manners.

 

The Edwards Plateau Ecoregion Dirty Dozen Terrestrial Invasive Species

These plants, identified by texasinvasives.org, are particularly worrisome invasive species in the Edwards Plateau ecoregion. Many of these are beautiful plants. Texas state law states that many plants identified by scentists as invasive and harmful are perfectly legal to sell. You will find them offered every spring and summer in the gardening department of major stores in our area. However, they spread quickly, easily and overwhelm the growth of native plants to the detriment on the wildlife that rely on them.  They invade the Texas Hill Country, a territory where there is no natural protection. Click on their common names to go to the Invasive Plant Database to identify each.

Glossy privet – Ligustrum lucidum
Chinese tallow tree – Triadica sebifera     ` leaves, fruit, sap are toxic to humans
Johnson grass – Sorghum halepense
Heavenly bamboo – Nandina domestica     – toxic to songbirds
Chinaberry tree – Melia azedarach     – mature plants produce fruit that is poisonous to humans, pets, livestock
Japanese honeysuckle – Lonicera japonica


Giant reed – Arundo donax   This particular clump, is located in the  Barons Creek drainage below Natural Grocers, Fredericksburg. photo by Jennifer Coulter.  Clogs waterways creating flooding situations in heavy rains.Will regrow from smallest root or stem.

 

Golden rain tree – Koelreuteria paniculata
Elephant ears – Colocasia esculenta
Paper mulberry – Broussonetia papyrifera
Tree of heaven – Ailanthus altissima     – sap can cause headaches and nausea when cutting and handling.
King Ranch bluestem – Bothriochloa ischaemum var. songarica     – little nutritional value for livestock.Wind borne seeds, create environment that crowds out native species.

Mediterranean Mustard – a Real “Bastard Cabbage”

Additional Invasives that damage the Texas Wildscape

Bermudagrass – Cyodon dactylon  – Native to Mediterranean regions of Europe and Africa. Releases chemicals that inhibits growth of other plants.

Lantana camara  – Indian Lantana -Also found in the nursery trade under the cultivar names: Confetti,  New Gold, and Dallas Red. Cross pollinates with native species. Prolific. spread by birds. 

Tall thistle alongside road
Malta starthistle out competing other plants along the road. Broad leaves of Texas thistle at lower right.

Malta star-thistle – Centaurea melitensis – Out competes native plants. Spines on the seeds prevent forage. Deep tap root.

 

Russian musk-thistle – Carduus nutans     – Forms dense carpets that cut out light to other plants. Depletes soil of nitrogen. Does not provide forage for wildlife or livestock due to spiny nature of plants. 

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About the Region

New Braunfels, the location of our Fall 2024 Symposium, straddles both the Edwards Plateau Ecoregion and the Blackland Prairie ecoregion. Interstate 35 divides the city of New Braunfels; its path through the city closely parallels the boundary of these two ecoregions, with the Edwards Plateau on the west side and the Blackland Prairies region to the east. The Edwards Plateau area is also called the Hill Country; however, this general term covers a much larger area extending farther north. Spring-fed creeks are found throughout the region; deep limestone canyons, rivers, and lakes (reservoirs) are common. Ashe juniper is perhaps the most common woody species found throughout the region. Additional woody species include various species of oak, with live oak (Quercus fusiformis) being the most common. Sycamores (Platanus occidentalis) and bald cypress (Taxodium distichum) border waterways. This area is well known for its spring wildflower displays, though they may be viewed in spring, late summer, and fall, as well. According to Texas Parks and Wildlife, average annual rainfall in the Edwards Plateau ranges from 15 to 34 inches.

The Blackland Prairie extends from the Red River south to San Antonio, bordered on the west by the Edwards Plateau and the Cross Timbers, and on the east by the Post Oak Savannah. Annual rainfall averages 30 to 40 inches, with higher averages to the east. This region is dominated by prairie species. The most common grass species include little bluestem (Schizachyrium scoparium) and Indian grass (Sorghastrum nutans) in the uplands and switchgrass (Panicum virgatum) in the riparian areas and drainages. Common herbaceous flowering plants include salvias, penstemons, and silphiums. This area has suffered greatly from overgrazing and agricultural use. Few intact areas remain, though many of the plants can be found along county roadsides throughout the region.

Our four host chapters (New Braunfels, Lindheimer, Guadalupe, and the Hill Country chapters) are located in one or both of the ecoregions above. However, the eastern portion of Guadalupe County also falls within the Post Oak Savanna ecoregion. Annual rainfall averages 35 to 45 inches, with higher averages to the east. A wide variety of hardwood trees are found, including several species of oaks, elms, and in the Bastrop area, loblolly pine (Pinus taeda). Grasses and forbs dominate in the open savannas, with most common grass being little bluestem. Ranching, agriculture, and fire suppression have allowed woody species to encroach on the once-open savannas.

Source: Wildflowers of Texas by Michael Eason