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,
- 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.
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. That limits the food supply for nesting birds and the larger, key wildlife species.
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.
*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.
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.
- 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 native plants.
- 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
Johnson grass – Sorghum halepense
Heavenly bamboo – Nandina domestica
Chinaberry tree – Melia azedarach
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.
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