March 2016
Lady Bird Johnson Wildflower Center Invasives Team Maps Invasive Plants at Big Thicket National Preserve

For eight days at the end of March, six intrepid workers from the Lady Bird Johnson Wildflower Center (JWC) worked to map invasive plants at Big Thicket National Preserve, northeast of Houston, TX. Under contract with the National Park Service (NPS) and led by Invasive Species Programs Coordinator Dr. Hans Landel of the JWC, the team was continuing its effort to map invasive plants in six national parks in the area managed by the NPS’s Gulf Region Exotic Plant Management Team. They have already mapped species in San Antonio Missions National Historical Park, and will be visiting Jean Lafitte National Historical Park and Preserve, Vicksburg National Military Park, Gulf Islands National Seashore, and Natchez Trace Parkway later in the year. The team is developing the protocol for mapping using computer tablets with geographical information system (GIS) software. The protocol will be used by NPS, and the data will enter the National Invasive Species Information System (NISIMS). NISIMS is the standard database system used by two other agencies in the Department of the Interior.

While at Big Thicket, the team braved snakes, mud, mosquitoes, spiny and thorny plants, and alligators while mapping trifoliate (or hardy) orange (Procirus trifoliata), golden bamboo (Phyllostachus aurea), common and giant salvinia (Salvinia minima and S. molesta), and water hyacinth (Eichhornia crassipes). Of these, trifoliate orange had the largest infestations. They found large patches of it, some covering more than a quarter of an acre, along the few miles of Big Sandy Creek they surveyed. Nothing was growing under the thickets. See the Invasive Species Highlight below for more information on this noxious species. While searching the backwaters along the Neches River, they were pleased to find that the recent flooding had swept the infestations of salvinia and hyacinth out to sea.

Other invasives they came across incuded Japanese climbing fern (Lygodium japonicum), Chinaberry (Melia azedarach) and Chinese tallow (Triadica sebifera). It was discouraging to see Chinese tallow in so many locations. In fact, there is so much of it that the Preserve staff must rate it as a low priority, even though within a few decades the Big Thicket's very character will have changed because of the widespread infestation.

The team really enjoyed the Preserve, even with the hard work, and thanks the Preserve’s staff for their help and support. They highly recommend you visit the preserve. Be prepared to see Chinese tallow in most places, though!

Keep track of the team on the Facebook page as they survey the other parks.

mapping trifoliate orange

Mapping trifoliate orange.

mapping golden bamboo

Mapping golden bamboo.


Forcing through a thicket of trifoliate orange.

searching for aquatic invasives

Searching for aquatic invasives.
Photo credits: Hans Landel, Lady Bird Johnson Wildflower Center

Invasive Spotlight:
Trifoliate (Hardy) Orange
Poncirus trifoliata

Trifoliate orange, also known as hardy orange, is a deciduous shrub or small tree that invades woodlands, forest edges, fence rows and urban green spaces. It can grow into large thickets, crowding out all other plants. Its large thorns make it especially problematic.

It grows from 8 to 30 ft. (2.4-9.1 m) high. The leaves are alternate, compound with three leaflets (trifoliate), up to 2 in. (5.1 cm) long and have a winged petiole. The twigs are green with stout, 1 in. (2.5 cm) or more long thorns. The bark is conspicuously green-striped. Spring flowers are white, 5-petaled, 1-2 in. (2.5-5.1 cm) in diameter and showy. Its fruit looks like a dull miniature orange, 1.5-2 in. (3.8-5.1 cm) in diameter, with a downy skin.

Hardy orange spreads mainly by dispersal of the fruit, which contain several seeds. Fruit can be carried downstream, where they come to rest in bottomlands; the several seeds then sprout, creating a new population.

Trifoliate orange was introduced from northern China as an ornamental due to its unique form and green color, beauty when flowering, and interest provided when fruiting. It was likely also planted as impenetrable hedges. Due to its hardy nature it is often used as rootstock for citrus trees.

Trifoliate orange needs to be watched closely since it can easily become established and create even more competition for desirable trees in forest settings. To prevent the spread of trifoliate orange, do not plant it; choose alternative plants, and eradicate the plants you find outside of a landscaped setting. Control can be achieved by hand pulling seedlings or, for larger specimens, the cut-stump application of an herbicide. Contact your local Texas A&M Forest Service or AgriLife office for specific recommendation and as always follow label directions. To be safe use basic precautions like gardening gloves, long pants & long sleeved shirts, and eye protection.

In Texas this invasive plant is found in mainly in the eastern woods.  It is found throughout the sourthern United States and up into Pennsylvania. 

(Some information for this article comes from this link)

Follow this link for more information on hardy orange.


Photographer: John D. Boyd
Source: Mississippi State University,


Credit: Diann Mabus, citizen scientist, Invaders of Texas

under trifoliate orange

Infestation in Big Thicket National Preserve.  Note there is nothing growing under the thicket.
Credit: Hans Landel, Lady Bird Johnson Wildflower Center


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If you would like your invasive species event or news listed in the next iWire, please send the details to


Sentinel Pest Network and Invaders of Texas Species Workshops

Invaders of Texas workshops train volunteers to become citizen scientists to detect and report invasive species. Workshops, which are free, include information on the Sentinel Pest Network, which serves to increase the awareness and early detection of the Emerald Ash Borer, Cactus Moth, Asian Longhorned Beetle, and other pests of regulatory significance.

Workshops are tailored to meet the interests of your volunteer group, and supplementary session examples include an introduction to the TX Invaders mobile application and the Eradicator Calculator, a feature on designed to help organize and track volunteer-based eradication efforts.

Upcoming Workshops:

Saturday, April 2, 2016
Location: Jesse H. Jones Park & Nature Center (Humble, TX)
Contact: Rosanne Belzung

For more information or to register to attend a free workshop, please visit the Workshop Page.