Watershed Newsletter
The Wimberley Valley Watershed Association

Protecting Jacob's Well and the Springs of the Wimberley Valley

The Top Ten Invasive Species in Texas


The Edwards Plateau is a land of canyons, caves, and springs. It has grasslands, juniper/oak woodlands, live oak savannahs and….Chinese Nandina! Invasive species are a monumental threat to habitat loss, second only to direct habitat destruction by development. State legislators and citizens need to implement stronger limitations very soon, starting with a ban on selling them in our nurseries.

Imagine that your favorite food and only food is pizza, and there are pizza bushes that you feast on every day. In fact, your family, going back hundreds of generations, has also done the same. Someone then decides to get rid of all the pizza bushes, as they want a plant that blooms French crepes. What will happen? You will have to leave the area, or die out.

Invasive plants are big players in the threats to almost half of the federally listed endangered species, and controlling them costs the US $137 billion annually. Gardeners are not too fond of how much work they put towards keeping them at bay.


Milkweed Leaf Beetle

Bugs and Insects: Wildlife species have evolved over time with area native plants. For example, the Milkweed is a host plant and primary food source for about 15 species, but for Monarch Butterflies, Milkweed Bugs, and Milkweed Leaf Beetles, it is their only food source. The Milkweed sap is poisonous to some animals, but not to the Monarch. It not only tolerates it, it results in a very bad tasting meal to its predators.

Water Tables: Invasive plant species have evapotranspiration rates higher relative to native flora, and can result in lower water tables.

Birds: The number and species richness of birds has a direct correlation with the volume of native plants in any given area. A South Texas study found that overall bird abundance was 32% greater on native-grass sites than on exotic-grass sites (Flanders et al. 2006).

Star Thistle
Currently, Bastard Cabbage tops the list of the least-desired plants. It is native to southern Europe and northern Africa, which once shared similar ecosystems with the Hill Country, having been connected tectonically. Bastard Cabbage now lines many Texas highways, crowding out native flowers. The Wildflower Research Center is attempting to handle the problem by seeding large amounts of Indian Blanket.

In addition, high infestations of Star Thistle are causing native species to experience drought conditions even with normal rainfall. Attempts at controlling the thistle have reduced the population by 50% in some areas, mainly through the use of insects. Mowing before the flowers set is also successful, if the there are no leaves left below the level of the cut.

The Edwards Plateau Dirty Dozen
Click on the link to learn to recognize these plants.
Glossy privet - Ligustrum lucidum
Chinese tallow tree - Triadica sebifera
Johnson grass - Sorghum halepense
Heavenly bamboo - Nandina domestica
Chinaberry tree - Melia azedarach
Japanese honeysuckle - Lonicera japonica
Giant reed - Arundo donax
Golden rain tree - Koelreuteria paniculata
Elephant ears - Colocasia esculenta
Paper mulberry - Broussonetia papyrifera
Tree of heaven - Ailanthus altissima
King Ranch bluestem - Bothriochloa ischaemum var. songarica

Adapted from the City of Austin’s Native Species Management Plan and Texas Invasives.org