Published data on the vascular flora of Erath County, Texas, is limited. In this investigation, data were obtained from vascular plant specimens deposited in the Tarleton State University Herbarium (TAC). Sixty-six new county records were recorded for Erath County. Major range extensions were documented for forty species, these having previously been known from at least one county away distant from the border of Erath County. Fourteen of the species are non-native while 52 species are native; only one of these, Yucca rupicola Scheele (Texas yucca), is endemic to Texas. No rare, threatened, endangered or state-listed noxious species were found.
Knowledge of regional Texas floras is crucial for understanding species composition for the state. In addition, such knowledge is important for the management and preservation of individual plant species and ecoregions across the state. Floristic data for Erath County, located in the southwestern portion of the West Cross Timbers, is poorly known. Having an updated list of vascular plants for a county is important for documenting changes in species distributions over time. This knowledge can be used in management plans for conserving endangered species, documenting the spread of invasive plants, and to improve the use of native species in restoration projects.
The Cross Timbers occur from Kansas to Texas, extending south into Texas about 256 km (Diggs et al. 1999). This forest dominated by post oak (Quercus stellata) and blackjack oak (Q. marilandica) grows on mildly acidic, sandy soils (Diggs et al. 1999). Poor agricultural practices and the suppression of fires has led to increased dominance of woody species and a loss of native grasses and climax understory vegetation (Dyksterhuis 1948). Invasions of woody plants such as mesquite (Prosopis glandulosa) and juniper (Juniperus ashei) in some native grasslands and forests throughout the region have occurred (Van Auken & Bush 1988).
When the Cross Timbers reaches the north-central boundary of Texas, it separates into two portions: the East and West Cross Timbers (Dyksterhuis 1948). The West Cross Timbers extends from the Grand Prairie west to the start of the Rolling Plains and contains timbered areas mixed with grasslands (Diggs et al. 1999). Erath County occurs in the southwestern portion of the West Cross Timbers, which has had few floristic studies in the past. The objective of this investigation were to inventory the vascular flora based on collections in the Tarleton State University Herbarium (TAC) that were not included in field investigations over the last decade (Harsley & Nelson 2010; Cowley et al. 2017; Cotton & Nelson 2018).
Materials & Methods
Vascular plant specimens from the Tarleton State University Herbarium were examined from Erath County. Each specimen was classified as native, endemic, or introduced using Shinners and Mahler’s Illustrated Flora of North Central Texas (Diggs et al. 1999). Plants from Erath County were compared to those which occur on the Texas state-listed noxious weeds list (USDA 2019), state threatened and endangered plant species list (TPWD 2020), and rare plants of Texas (Poole et al. 2007). Distributions of taxa were compared to those published in the Atlas of the Vascular Plants of Texas (Turner et al. 2003a; 2003b). Based on data from the atlas, we categorized our specimens as documenting major range extensions (taxa collected in Erath County but not known from adjacent counties.
Results & Discussion
Sixty-six species representing 25 families were identified as new records from Erath County. Fifty-two taxa are native or endemic and 14 are introduced species. Yucca rupicola Scheele (Texas yucca) was the single endemic species collected. No species were found that were included on the state noxious weeds list (USDA 2019). There were no rare (Poole et al. 2007), threatened, endangered, or state-listed plant species (TPWD 2020).
Of the 66 species identified, 26 are considered new county records for Erath County but also are found in adjacent counties (Table 1). We report major range extensions for forty taxa (Table 1), which are discussed individually in the following paragraphs. These taxa have not previously been reported from Erath County or from adjacent counties.
Crepis pulchra L.—Showy hawk’s-beard is an introduced weed reported from only five counties in Texas (Turner et al. 2003a). This Eurasian native occurs in disturbed areas (Diggs et al. 1999) and our specimen represents its expansion into a sixth county in the state.
Eupatorium coelestinum L.—Mistflower is a native species found in moist, sandy or calcareous soils usually in woody areas (Diggs et al. 1999). The closest-known collection locality is from Parker County and it the species generally occurs in the eastern one-half of Texas (Turner et al. 2003a).
Krigia cespitosa (Raf.) K. L. Chambers var. cespitosa—Weedy dwarf-dandelion is a native species that occurs in sandy soil along stream banks, in damp woods, and disturbed areas (Diggs et al. 1999). It has previously been reported from east and north central Texas (Turner et al. 2003a); Our specimen documents its presence in Erath County within the southwestern Cross Timbers.
Descurainia pinnata (Walter) Britton subsp. pinnata—Pinnate tansy-mustard is a native member of the mustard family that occurs in sandy soils in a variety of habitats (Diggs et al. 1999). It has previously been known from counties surrounding Erath County but not bordering it directly (Turner et al. 2003a); our specimen indicates its range extension into that gap.
Matthiola longipetala (Vent.) DC.—Eveningstock is an introduced species that escapes cultivation (Diggs et al. 1999) with its only previously known locality in Bell County (Turner et al. 2003a). Our specimen, from Erath County, extends its range northward into the southwestern Cross Timbers.
Raphanus sativus L.—Radish is a cultivated species that can become naturalized when it escapes from garden plots (Diggs et al. 1999). It is known from scattered localities in the southern part of the state (Turner et al. 2003a); our specimen from Erath County extends its range northward into the southwestern Cross Timbers.
Rorippa nasturtium-aquaticum (L.) All.—Watercress is a native species that occurs in shallow, fairly clear streams or springs and is sometimes stranded in mud (Diggs et al. 1999). The known range for watercress is scattered across the state (Turner et al. 2003a) and our specimen extends its known range into Erath County along the Paluxey River.
Opuntia humifusa (Raf.) Raf.—Eastern prickly-pear is a native cactus that occurs in open, dry areas (Diggs et al. 1999). This specimen was found in openings of a sand post oak (Q. margarettae) community. According to Turner et al. (2003a) the closest known locality is Brown County; our specimen extends the distribution eastward.
Lonicera maackii (Rupr.) Maxim.—Bush honeysuckle is an introduced honeysuckle previously reported from Brazos, Dallas, and Tarrant counties (Turner et al. 2003a). Our specimen increases the number of counties from which this plant is known in Texas.
Minuartia drummondii (Shinners) McNeill—Drummond’s sandwort is a native sandwort that occurs in sandy or sandy-clay soils of disturbed areas mainly in southeast and east Texas (Diggs et al. 1999). It has been reported mainly from the eastern half of Texas and our specimen extends its range to Erath County (Turner et al. 2003a).
Carex granularis Muhl. ex Willd.—Granular caric sedge is a native species previously known only from northeast Texas (Turner et al. 2003a). Our specimen extends its range southwest into Erath County.
Chamaesyce stictospora (Engelm.) Small—Slim-seed euphorbia is a native spurge found in clay soils on limestone slopes, prairies, and disturbed sites primarily in west Texas but with scattered localities eastward to the East Cross Timbers and Dallas County (Diggs et al. 1999). Our specimen adds Erath County to the known distribution of the species.
Acacia roemeriana Scheele—Catclaw is a native small tree or shrub that occurs in rocky or sandy areas (Diggs et al. 1999) primarily in central and west Texas (Turner et al. 2003a). Our specimen extends the range of catclaw to the northeast.
Baptisia bracteata Muhl. ex Elliott var. leucophaea (Nutt.) Kartesz & Gandhi—Plain’s wild indigo is a native herb that occurs in sandy areas (Diggs et al. 1999). It is known from East Texas (Turner et al. 2003a) and our specimen extends its known range westward into Erath County.
Dalea purpurea Vent.—Purple prairie-clover is native and found on sandy prairies west of Erath County and to Tarrant County (Diggs et al. 1999). Turner et al. (2003a) show scattered occurrences across the state with known localities in Mills, Parker and Tarrant counties. Our specimen from Erath County is between these known localities.
Rhynchosia latifolia Nutt. ex Torr. & A. Gray—Broad-leaf snout-bean is a native snout-bean that occurs in sandy woods and roadsides (Diggs et al. 1999) that has been reported from the eastern third of Texas and a far western locality in Hardeman County (Turner et al. 2003a). Our specimen documents another western extension of its known range into Erath County.
Trifolium repens L.—White clover is an introduced species that occurs in disturbed areas (Diggs et al. 1999). Our specimen extends the known range of the species into Erath County.
Juncus dudleyi Wiegand is a native rush that occurs in low areas (Diggs et al. 1999). Its known distribution is scattered over the state with Llano County being the previously-reported site closest to Erath County (Turner et al. 2003a). Our specimen provides evidence for its presence in Erath County.
Calamintha arkansana (Nutt.) Shinners—Ozark savory is a native mint that occurs on calcareous rock outcrops (Diggs et al. 1999). It is known from east and south of Erath County (Turner et al. 2003a). Our specimen extends its range northwestward from known locations.
Salvia greggii A. Gray—Gregg’s sage is a native species that occurs in rocky soils, primarily in the Trans-Pecos and Edwards Plateau (Diggs et al 1999). Our specimen extends its known range (Turner et al. 2003a) north and eastward into Erath County. The plant was collected in a riparian area of a city park surrounded by housing additions. We hypothesize that it was introduced from landscaping in the area and is becoming naturalized.
Lythrum californicum Torr. & A. Gray—California loosestrife is a native species that occurs in low, moist soils (Diggs et al. 1999) and is reported from the western two-thirds of Texas with several notable distribution gaps. The closest previously reported locality is Brown County and our specimen from Erath County helps to fill one of these gaps in the known distribution (Turner et al. 2003a).
Aristida purpurascens Poir.—Arrow grass is a native grass that has been collected in Parker County (Turner et al. 2003b). It is usually found on sandy soils in a variety of habitats (Diggs et al. 1999) and our specimen extends its range southward into Erath County.
Aristida purpurea Nutt. var. wrightii (Nash) Allred—Wright’s threeawn is a native grass that has been reported from Brown County (Turner et al. 2003b) and is known to occur in calcareous soils in the Blackland Prairie (Diggs et al. 1999). Our specimen extends its range westward into Erath County.
Bromus secalinus L.—Rye brome is native to Europe and widespread in Texas (Diggs et al. 1999). Our specimen fills a gap in the known range of the species, the closest previously known locality being Tarrant County (Turner et al. 2003b).
Sphenopholis obtusata (Michx.) Scribn.—Prairie wedgescale is a native grass previously known from as close as Brown County (Turner et al. 2003b); our specimen extends its range eastward into Erath County.
Platanus occidentalis L.—American sycamore is a native tree found in stream bottoms and as a planted tree (Diggs et al. 1999). The closest locality from which American sycamore is reported is Coryell County to the south, although it is also known from Tarrant County to the northeast (Turner et al. 2003a). Our specimen fills in the distribution gap between these localities to the northeast and south.
Ranunculus parviflorus L.—Sticktight buttercup is native to Europe and occurs on damp soils (Diggs et al. 1999). It has been reported mostly from East Texas but has been collected as far west as Gillespie County (Turner et al. 2003a). Our specimen extends the known range of sticktight buttercup in Texas.
Rosa multiflora Thunb. ex Murr.—Japanese rose is an introduced rose from Asia that occurs in weedy areas (Diggs et al. 1999). It is known from Tarrant County to the northeast and Lampasas County to the south (Turner et al. 2003a) and our specimen documents its occurrence in Erath County.
Physalis longifolia Nutt. var. longifolia—Common ground-cherry is a native species that occurs in open woods and prairies throughout most of Texas (Diggs et al. 1999). However, it has not been reported from Erath or surrounding counties, and our specimen connects disjunct eastern and western ranges (Turner et al. 2003a).
We wish to thank Bethany Oneal and Becky Nelson for their TAC herbarium work. We also appreciate manuscript reviews by D. Lemke and J. Singhurst that improved the manuscript.