Expected List: non-native species likely to soon appear in Texas as invasive and ecologically damaging
The Expected List records species not currently known with certainty in Texas but that occur in nearby areas. Each of these is aggressively invasive and ecologically damaging, and there is a high probability that each soon will reach Texas (see caveat for Melaleuca). As with the Super Watch List, the possibility exists that early establishments of these species can be eradicated, and their potential occurrence should receive particularly close monitoring.
This account has been formed at the suggestion of Dr. Norma Fowler of the University of Texas and with her input. More species are to be added. The listings of states are from the USDA PLANTS Database.
Alliaria petiolata (M. Bieb.) Cavara & Grande (Garlic mustard). Herbaceous. Native to Europe, North Africa, Sri Lanka, and India. A biennial herb planted as a garden ornamental, now escaped abundantly from Quebec and Ontario, south to North Carolina and Kentucky, and west to Kansas and North Dakota; USA (AK, AR, CO, CT, DC, DE, GA, IA, ID, IL, IN, KS, KY, MA, MD, ME, MI, MN, MO, NE, ND, NE, NH, NJ, NY, OH, OK, OR, PA, SC, TN, UT, VA, VT, WA, WI, WV), CAN (BC, NB, NS, ON, QC); expected in north Texas. It invades forested natural areas and can dominate the ground-level vegetation.
Ampelopsis brevipedunculata (Maxim.) Trautv. (Porcelain berry). Woody vine. Native to northeastern Asia. Originally cultivated in the USA as a bedding and landscape plant, now spreading quickly by abundant production of berries in the eastern states; USA (CT, DC, DE, GA, IA, IL, KY, MA, MD, MI, NC, NH, NJ, NY, OH, PA, RI, VA, WI); expected in east Texas. It invades open woods and woods edges. Porcelain berry is in the grape family and is often confused with species of grape (Vitis) and with native species of Ampelopsis -- A. arborea and A. cordata.
Berberis thunbergii DC. (Japanese barberry). Native to Asia. Woody. Extremely invasive in recent years in the East and Midwest; USA (CT, DC, DE, GA, IA, IL, IN, KS, KY, MA, MD, ME, MI, MN, MO, NC, ND, NE, NH, NJ, OH, PA, RI, SC, SD, TN, VA, VT, WV, WY), CAN (NB, NS, ON, PE, QC); expected in north and east Texas. Capable of forming dense thickets.
Celastrus orbiculatus Thunb. (Oriental bittersweet). Woody. Native to Japan, Korea, and China. A deciduous, climbing, woody vine originally introduced as an ornamental, now escaping cultivation from Maine to Georgia and west to Minnesota; USA (AR, CT, DC, DE, GA, IA, IL, IN, KY, MA, MD, ME, MI, NC, NH, NJ, NY, OH, PA, RI, SC, TN, VA, VT, WI, WV), CAN (NB, ON, QC); expected in east Texas. It grows at old home sites, fields, and road edges; shade tolerance allows it to also grow in open forests. The vines can completely cover other vegetation and shade, out-compete, and kill even large trees. The berries are eaten by birds and the seeds spread quickly. It has been shown to hybridize with American bittersweet (Celastrus scandens), potentially leading to a loss of genetic identity.
Centaurea stoebe ssp. micranthos (Gugler) Hayek (= Centaurea biebersteinii DC.; C. maculosa authors) (Spotted knapweed). Herbaceous. Native to Central Europe, east to central Russia, Caucasia, and western Siberia. Introduced to North America from Eurasia as a contaminant in alfalfa and possibly clover seed, and through discarded soil used as ship ballast. It is reported to occur throughout Canada and in every state in the U.S. except Alaska, Georgia, Mississippi, Oklahoma and Texas; expected to occur widely in Texas. Spotted knapweed infests many habitats, including fields, roadsides, forests, prairies, meadows, pastures, and rangelands, a horrible weed.
Centaurea solstitialis L. (Yellow star thistle). Moved to known occurrence, F1, May 2010.
Cirsium arvense (L.) Scop. (Canada thistle). Herbaceous. Native to Eurasia. It arrived in North America in the early 1600's and has now spread widely; USA (AK, AL, AR, AZ, CA, CO, CT, DC, DE, IA, ID, IL, IN, KS, KY, MA, MD, ME, MI, MN, MO, MT, NC, ND, NE, NH, NJ, NM, NV, NY, OH, OR, PA, RI, SD, TN, UT, VA, VT, WA, WI, WV, WY), CAN (AB, BC, MB, NB, NF, NS, NT, ON, PE, QC, SK, YT), DEN (GL), FRA (SPM); expected to occur widely in Texas. It is an unusual thistle in its dioecious habit, the heads either with staminate or pistillate flowers and separated on different plants, and in its rhizomatous reproduction, quickly spreading by fragmentation of the rhizomes. It is a pernicious weed.
Dioscorea alata L. (Winged yam). Herbaceous. Native to Southeast Asia. Introduced in Florida as an ornamental, perhaps for the curiosity of its aerial tubers and for its large, opposite, heart-shaped leaves with radiating veins. Now naturalized and becoming aggresively invasive in the Gulf Southeast; USA (FL, GA, LA), USA+ (PR, VI); expected in east and south Texas. Winged yams are herbaceous, deciduous vines that can form blankets of overlapping leaves over native vegetation and may cover even entire trees. Each plant originates from an underground tuber that can weigh up to 100 pounds; these are edible and widely used for food. The main means of reproduction and dispersal for winged yam are the potato-like aerial tubers produced at the leaf axils; fertile seeds are rarely produced.
Winged yam is closely related to the air-potato (Dioscorea bulbifera, see Watch List), which has alternate leaves, more numerous aerial tubers, but underground tubers small or absent.
Elaeagnus pungens Thunb. (Thorny olive). Woody. Native to Asia. Planted as hedges and now escaping into the woods in the southeastern USA; USA (AL, DC, FL, GA, KY, LA, MA, MS, NC, SC, TN, VA); expected in east Texas. Capable of forming dense thickets.
Elaeagnus umbellata Thunb. (Autumn olive). Woody. Native to Afghanistan, China, Korea, and Japan. Widespread in the eastern USA, including Lousiana and Arkansas; USA (AL, AR, CT, DC., DE, FL, GA, HI, IA, IL, IN, KS, KY, LA, MA, MD, ME, MI, MO, MS, MT, NC, NE, NH, NJ, NY, OH, OR, PA, RI, SC, TN, VA, VT, WA, WI, WV), CAN (ON); expected in eastern and north Texas. Produces dense, thorny thickets. The plants produce fleshy fruits that are widely spread by birds.
Euonymus alatus (Thunb.) Siebold (Burning bush). Woody. Native of Asia. Planted mostly as a hedge and escaping cultivation in the eastern USA and Midwest; USA (CT, DC, DE, GA, IA, IL, IN, KY, MA, MD, MI, MO, MT, NC, NH, NJ, NY, OH, PA, RI, SC, VA, VT, WI, WV), CAN (ON); expected in east and north Texas. Replaces native shrubs.
Euonymus fortunei (Turcz.) Hand.-Mazz. (Wintercreeper). Woody. Native to Asia. Introduced in USA as an evergreen groundcover and now invading forests in the eastern and midwestern states southward; USA (CT, DC, DE, GA, IL, IN, KS, KY, MA, MD, MI, MO, MS, NC, NJ, NY, OH, PA, RI, SC, TN, VA, WI), CAN (ON); expected in east and north Texas. Very commonly cultivated in Texas, and as in cultivation, it forms dense mats as an escape. Flowers and fruits apparently are not commonly formed in Texas.
First report for Texas: Tarrant Co., Fort Worth, northeast end Overton Park, large clone(?), ca. 6 square feet, bank of drainage at edge of thicket, possibly washed downslope from house ca. 50 feet upslope, with Prunus caroliniana, Photinia serratifolia, Celtis laevigata, 18 May 2009, G.L. Nesom 09-01 (TEX, to be deposited).
Euphorbia esula L. (Leafy spurge). Herbaceous. Native to Europe. Planted as an ornamental and now widely escaped in the north and central plains states as well as in the West; USA (AZ, CA, CO, CT, DE, IA, ID, IL, IN, KS, MA, MD, ME, MI, MN, MO, MT, ND, NE, NH, NJ, NM, NV, NY, OH, OR, PA, SD, UT, VA, VT, WA, WI, WV, WY), CAN (AB, BC, MB, NB, NS, ON, PE, QC, SK, YT); expected in west and north Texas. Especially aggressive in dry situations, often completely displacing native forbs and grasses. It reproduces by seeds and by crown and root buds.
Halogeton glomeratus (M. Bieb.) C.A. Mey. (Saltlover). Herbaceous. Native to southeastern Russia and northwestern China. Introduced into North America as late as 1930 and now invasive in the western USA; USA (AZ, CA, CO, ID, MT, NE, NM, NV, OR, SD, UT, WA, WY); expected in west Texas. Halogeton has become common in dry deserts, barren areas, overgrazed prairies, burned-over areas, roadsides, dry lakebeds, and other disturbed areas, especially abundant in alkaline or saline soils.
Lonicera morrowii A. Gray (Morrow's honeysuckle). Woody. Native to eastern Asia and first introduced into North America in the late 1800s as an ornamental and for wildlife food and cover; USA (AR, CO, CT, DC, DE, IA, IL, KY, MA, MD, ME, MI, MN, MO, NC, NH, NJ, NM, NY, OH, PA, RI, SC, TN, VA, VT, WI, WV, WY), CAN (NB, ON, QC, SK); expected in north and northwest Texas. It invades open woodlands, old fields, and other disturbed sites, the fruits rapidly dispersed by birds and mammals, and forming dense thickets.
Lygodium microphyllum (Cav.) R. Br. (Small-leaf climbing fern). Herbaceous. Native to southeastern Asia. Introduced as an ornamental, now abundant in the southern half of peninsular Florida and said to have expanded into Alabama and Mississippi; expected in south and east Texas. It can climb high into trees and sometimes forms thick mats on the ground. Both L. microphyllum and L. japonicum (already widespread in east Texas) are highly self-fertile, and their microscopic spores are dispersed rapidly and widely by wind.
Melaleuca quinquenervia (Cav.) Blake (Melaleuca, punk tree, paperbark). Woody. Native to Asia, Australia, and Pacific Islands. Initially planted in Florida for landscaping, quickly to become regarded as a highly aggressive and destructive species in the southern half of the peninsula; now also reported to occur in southeast Louisiana (Orleans and Jefferson parishes); FL, LA; possibly expected to appear in wetlands of southeast Texas. Melaleuca trees typically are emergent semiaquatics and form dense thickets in wet or intermittently wet subtropical prairies and marshes –– it is perhaps the most serious threat to the Everglades, along with the Brazilian Pepper Tree (Schinus terebinthifolius). Even young melaleuca trees can produce huge numbers of seeds in capsular fruits that remain closed and on the plants until some form of stress causes them to open and release the seeds. Its potential appearance in Texas probably would be through wind-borne seeds, although viable seeds also can be carried by water, and the inadvertent transport of seeds by car or truck always is possible. The expectation that melaleuca will reach Texas is not as great as for the other species in this list, but the possibility still is distinct.
Miscanthus sinensis Anderss. (Chinese silvergrass). Herbaceous. Native to Asia. Introduced into the USA as an ornamental during the late 1800s and still widely sold, now invasively widespread in the eastern states; USA (AL, CA, CO, CT, DC, DE, FL, GA, IL, KY, LA, MA, MD, MI, MO, MS, NC, NJ, OH, PA, RI, SC, TN, VA, WV), CAN (ON); expected in east Texas. It invades roadsides, forest edges, old fields, and other disturbed areas.
“Miscanthus sinensis is the premier ornamental grass –– a garden favorite for centuries. There are literally hundreds of cultivars, differing in blade size, shape and color pattern; plant height and texture; summer, autumn and winter foliage colors; flower timing and color; and cold hardiness” (from the horticultural site www.Floridata.com). It is already widely cultivated in north and east Texas.
Phalaris aquatica L. (Harding grass). Herbaceous. Native to Europe and Asia. Introduced into the northern USA for forage and now naturalized across the continent; USA (AZ, CA, DC, HI, MS, MT, NC, OR, SC, VA); expected in Texas. Harding grass invades drainages and other wetland habitats, including wet prairies in the Midwest. It spreads vegetatively and forms dense stands covering large acreages. The species has been attributed to Texas by the PLANTS Database on the basis of its listing in Hatch et al. (1990), but vouchers apparently are from cultivated plants.
Pennisetum setaceum (Forsk.) Chiov. (Fountain grass, crimson fountaingrass). Herbaceous. Native to Africa. Widely introduced as an ornamental grass for its large, pink to purple inflorescences. USA (AZ, CA, CO, FL, HI, LA, NM, OR, TN); expected in north and west Texas and perhaps elsewhere, since it is now commonly cultivated in our state. Fountain grass is a highly aggressive, fire-adapted colonizer; it has a wide elevational range but is said to be limited to areas with a median annual rainfall of less than 50 inches.
Polygonum cuspidatum Siebold & Zucc. (= Fallopia japonica Siebold & Zucc.) (Japanese knotweed). Herbaceous. Native to eastern Asia. Introduced as an ornamental and now outside of cultivation over most of the eastern and northern USA and lower Canada; USA (AK, AR, CA, CO, CT, DC, DE, GA, IA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, NE, NH, NJ, NY, OH, OK, OR, PA, RI, SC, SD, TN, UT, VA, VT, WA, WI, WV), CAN (BC, MB, NB, NF, NS, ON, PE, QC), FRA (SPM); expected in north, east, and west Texas. It forms dense stands, especially along riverbanks and wet areas. The rhizomes fragment and small pieces are able to regenerate.
Schismus arabicus Nees (Arabian schismus). Herbaceous. Native to Africa, Asia, and Europe. Now spreading the in western states; USA (AZ, CA, NM, NV, UT); expected in west Texas. It has become an important components of the winter-early spring annual vegetation of the Mojave and Sonoran deserts, especially in disturbed or open areas among shrubs, roadsides, fields, and dry river beds.
Setaria faberi Herrm. (Giant foxtail, Japanese bristlegrass). Herbaceous. Native to Asia. Accidentally introduced in the United States in the 1920s as a contaminant of other grain. Reported by PLANTS Database from IL, PA, OH, TN, VA; EDDMapS shows it from many more states, including Louisiana, Arkansas, and Kansas; expected in east Texas. Giant foxtail invades disturbed sites such as roadsides, landfills, fence rows and right of ways.
Typha angustifolia L. (Narrowleaf cattail). Herbaceous. Native to Eurasia. Some studies have suggested that it was early introduced from Europe into Atlantic Coastal North America and migrated westward (Stuckey & Salamon 1987). USA (AR, CA, CO, CT, DC, DE, IA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MT, NC, ND, NE, NH, NJ, NM, NV, NY, OH, OK, OR, PA, RI, SC, SD, TN, VA, VT, WA, WI, WV, WY); CAN (BC, MB, NB, NS, ON, PE, QC, SK) Expected to occur widely in Texas; perhaps here already, confused in ID with Typha domingensis? Because of confusion in identification with T. domingensis, range expansion in recent years, and undercollecting, the distribution on the margins of the main range of T. angustifolia is somewhat uncertain.
Wisteria floribunda (Willd.) DC. (Japanese wisteria). Woody vine. Native to Japan, introduced in North America in the mid-1800s as an ornamental -- popular in the southern states as a decorative addition to porches, gazebos, walls, and gardens. USA (AL, AR, DC, FL, GA, IL, KY, LA, MA, MD, ME, MS, NC, NH, NJ, OH, PA, SC, TN, TX, VA); erroneously reported for texas; expected in east Texas. It is capable of forming dense thickets and can kill trees by girdling or over-topping, climbing up to 20 meters high.
Attributed to Texas by the PLANTS Database on the basis of Duncan (1967), but Duncan did not map this species for Texas; not attributed to Texas by Isely (1998). Excluded from the Texas flora.
Duncan, W.H. 1967. Woody vines of the southeastern states. Sida 3: 1–76.
Last update: 18 May 2010 (Centaurea solstitialis moved to known occurrence)