Rhus aromatica and R. trilobata have been treated as distinct species and the same species over the years with little explanation in the Texas flora as to why. Although a much more thorough investigation into the literature would be preferable, I'll just go through the classic Texas references (I would ordinarily include FNA, but the Anacardiaceae treatment hasn't come out yet). Firstly, here are the three names and their equivalents under the two taxonomies:

R. aromatica var. serotina = R. aromatica var. serotina
R. aromatica var. flabelliformis = R. trilobata var. trilobata
R. aromatica var. pilosissima = R. trilobata var. pilosissima

Manual of the Vascular Plants of Texas considers R. trilobata a synonym of R. aromatica with little explanation.
Flora of North Central Texas considers the two species separate but notes the following: "This taxon [R. trilobata] is distinguished in some instances with difficulty from R. aromatica and is possibly only a variety of that species."
Atlas of the Vascular Plants of Texas synonymizes R. trilobata under R. aromatica without any explanation.
Flowering Plants of Trans-Pecos Texas and Adjacent Areas considers R. trilobata a synonym citing Atlas of the Vascular Plants of Texas.
The taxon merge on iNaturalist was made citing this: https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=41175. Jepson cites this: https://www.jstor.org/stable/25064252?seq=1. The phylogeny paper gives no indication that the two should be treated as synonyms. Indeed, there is not enough populational data mapped in the paper to give a conclusion one way or another meaning that the decision is based on the experience of the authors (John M. Miller & Dieter H. Wilken). This is fine, but it still doesn't offer any populational explanation as to what is going on in the species and why the decision to synonymize was made.

Until a more thorough study is done or I find some better references, I'll be following suit and not recognizing R. trilobata. Please let me know if you have a reference that offers a view with greater depth than the above as there doesn't seem to be much in the way of explanation in the Texas literature on Rhus.

The best distinctions are given in Manual of the Vascular Plants of Texas and are as follows:
Terminal leaflets 25-60 mm long, more or less narrowed at apex.....................R. aromatica var. serotina
Terminal leaflets 15-33 mm long, abruptly narrowed to truncate at apex
Mature leaves glabrous....................R. aromatica var. flabelliformis
Mature leaves densely pubescent.....................R. aromatica var. pilosissima

Rhus aromatica var. serotina doesn't appear to occur on the High Plains/Rolling Plains.

Rhus aromatica var. flabelliformis in truly glabrous form appears to be somewhat uncommon in the region, but many individuals have leaves so sparsly pubescent that it is hard to consider them R. aromatica var. pilosissima. As good varieties, there is going to be intergradation. Here is one of the few glabrous examples in the area: https://www.inaturalist.org/observations/13131983. Even it has a little hair.

R. aromatica var. pilosissima seems to be the most common variety on the Llano Estacado and adjacent areas. The most extreme and obvious examples of this variety are when the hairs are densely pilose and produce a velvety texture. This form is common.

Two species of Townsendia occur on the High Plains: T. texensis and T. exscapa.

Plants annual/biennial, not caespitose; internodes usually visible through leaves by second flower head anthesis; leaf hairs usually appressed but not strictly so; ray flowers purple at anthesis.............T. texensis (BONAP; FNA)
Plants strong perennial, caespitose; internodes not visible through the leaves at any stage; leaf hairs strictuly appressed; ray flowers white at anthesis..................T. exscapa (BONAP; FNA)

I figured I'd share what I've been working on. This is just a draft, but should help with the Astragalus IDs. This includes only the Texas material and will likely need a couple of New Mexico species added before this is complete. Also, I have not included the key to varieties of A. mollissimus yet. Distributions are based on Turner et al. 2003 (Atlas of the Vascular Plants of Texas).

Robust white-flowered species
,1. Plants glabrous or nearly so............A. praelongus
,1. Plants hairy..........................................2
,2. Hairs on calyces appressed, not bluish; pedicels attached at the middle of flat, proximal part of calyx; leaves green; adaxial side of leaves glabrous or nearly so......A. racemosus
,2. Hairs on calyces not appressed, bluish; pedicels attached at the base of flat, proximal part of calyx; leaves silvery; adaxial side of leaves hairy......................S. nuttalliana

Prostrate perennial species
,1. Plants glabrous or nearly so.......A. lentiginosus var. higginsii
,1. Plants hairy.......................2
,2. Leaflets of apical leaves more than 2.5x longer than wide....3
,2. Leaflets of apical leaves less than 2.5x longer than wide....4
,3. Plants producing many long creeping stems; apical leaves with strongly conduplicate leaflets.......A. crassicarpus var. crassicarpus
,3. Plants appearing nearly caespitose with few very short stems; leaflets conduplicate or not....A. lotiflorus
,4. Leaflets glabrous or nearly so adaxially; stems shaggy..............A. plattensis
,4. Leaflets densely hairy, silvery; stem hairs various.................5
,5. Plants strictly and regularly strigose; hairs appressed......................A. missouriensis
,5. Hairs shaggy, if appressed, some hairs not so producing a silvery effect.....A. mollissimus

A. plattensis and A. crassicarpus are very close and should be keyed in the same couplet once I figure out the finer distinctions.

Key by fruits
,1. Fruits glabrous or nearly so..........2
,1. Fruits hairy..........................10
,2. Fruits at least 3x longer than wide..........3
,2. Fruits less than 3x longer than wide.........6
,3. Fruits trigonous, not falcate; plants erect perennials with white flowers.......................................................A. racemosa
,3. Fruits not trigonous, falcate at least proximally; plants prostrate annuals with purple to occasionally white flowers (usually due to fading)........................................4
,4. Fruits not prominently grooved abaxially, appearing somewhat flattened; banner purple, wing petals white for apical 1/2 to 2/3rds, not purple tiped; plants large, prostrate.............A. lindheimeri
,4. Fruits prominently grooved abaxially, rounded in cross-section; banner purple to lavender or nearly white, wing petals usually white with purple or lavender stripe on ventral margin extending to tip, sometimes entire tip purple or purplish; plants small, usually ascending early on and becoming prostrate later.............5
,5. Leaves truncate or emarginate.....A. nuttallianus
,5. Leaves not as above...............A. austrinus var. austrinus
,6. Fruits mottled; leaves slenderer than A. gracilis; likely absent in the area.......A. ceramicus var. filifolius (likely absent)
,6. Not as above..............................................................................7
,7. Fruit narrowing proximally nearly to a stipe; robust, white-flowered plants...........A. praelongus
,7. Not as above..........................................................................8
,8. Fruits strongly falcate, not inflated.............A. mollissimus
,8. Fruits either not falcate, or inflated............9
,9. Fruits papery, not pigmented at maturity; plants essentially glabrous.....A. lentiginosus var. higginsii
,9. Fruits not papery, often pigmented; plants strigose.......................A. crassicarpus var. crassicarpus
,10. Fruits tiny (less than 5 mm long), roughly oblong-oval, and numerous along the inflorescence, often more than 10.....A. gracilis
,10. Fruits larger (more than 5 mm long), various in shape, and fewer, sometimes numerous usually less than 10............11
,11. Plants spring ephemerals; fruits linear..........A. austrinus (var. trichocarpa or var. austrinus depending on hair density)
,11. Plants larger perennial; fruits not linear...........12
,12. Fruits narrowing proximally to a stipe............Sophora nuttaliana
,12. Fruits not narrowing proximally...................13.
,13. Immature fruits obscurred by the corolla; mature fruits usually halfway obscured by the sepals....................Oxytropis lambertii
,13. Not as above; calyces obscuring less than a quarter at maturity or absent altogether.........................14
,14. Fruit hairs not appressed............A. lotiflorus (in part; cleistogamous plants)
,14. Fruit hairs appressed................15
,15. Mature fruits less than 2x longer than wide (not including style)..........A. plattensis
,15. Mature fruits more than 2x longer than wide (not including style)..........16
,16. Fruits gradually curved abaxially; leaflets produced during flowering usually oval or eleptical, less than 3x longer than wide...............................................A. missouriensis
,16. Fruits straight for first 2/3rds then curving sharply abaxially; leaflets produced during flowering usually narrowly elliptical, more than 3x longer than wide.............A. lotiflorus

Here is some information on the Oenothera species of the Llano Estacado.
BONAP

[DRAFT! -
The erect members of sect. Oenothera and the members of sect. Anogra have not been given characteristics to distinguish. Also, I hope to add some more links and maybe photos to the individual species. However, I figure it's better to make this available now so people can review the same document as I am as I ID the members of Oenothera. Just remember that this is a draft, and I will be updating this as I learn more and have time to add more. Lastly, there are species I haven't filled in as much as I want to. Keep this in mind as you use this and let me know if there's a specific species you're having trouble with that isn't really specific enough in the descriptions provided here.]

Sect. Calylophus

Oenothera capillifolia (Calylophus capillifolia; C. berlandieri) - Buds strongly 4-angled, keeled at sepal margins; leaves serrated. Styles long, stigmas held to the apices of the outer series of anthers or beyond; petals trending slightly larger than O. serrulata. Widespread mostly in sandy soils.

Oenothera capillifolia subsp. berlandieri (Calylophus berlandieri subsp. berlandieri) - Plants multistemmed, spreading, sometimes shrubby perennials; flower throat and stigmas never black. Widespread in sandy soils.

Oenothera capillifolia subsp. capillifolia (Calylophus berlandieri subsp. pinifolia; Calylophus capillifolia) - Plants single or few-stemmed annuals to short-lived perennials; flower throats and stigmas yellow or black. If pressent on the Llano Estacado, restricted to the eastern margins, probably absent on the High Plains.

Oenothera gayleana - Buds strongly 4-angled, keeled at sepal margins. Gypsum in Trans-Pecos and north Rolling Plains region; probably absent on the High Plains.

Oenothera serrulata (Calylophus serrulata) - Buds strongly 4-angled, keeled at sepal margins; leaves serrated. Styles short, stigmas held to the apices of the inner series of anthers at most; petals trending slightly smaller than O. capillifolia. Present; details not yet available. After considerable searching on iNaturalist, I have found maybe 2 or 3 observations with this style characteristic. Also, the style characteristic seems somewhat variable and inconsistent in individual plants (perhaps even to the point of calling the flowers heteromorphic). However, there are no other characters from the treatments that I've read that can be relied upon (petal length has more overlap than not). Furthermore, O. capillifolia subsp. capillifolia often has very short anthers and short styles (the morphotype that appears annual and without black stigma or floral tube). There is a lot of complexity in this group and I'm not really sure how to make sense of it at present other than to mark those with the key characteristic as O. serrulata even if the taxonomic support for that is poor. I'll keep looking for more information. Here are the observations I'm referencing: plant like O. capillifolia subsp. berlandieri with strongly heteromorphic styles (due to genetics or aberrance, I'm not sure); the most reliably short-styled plant I've found; and styles short, but heteromorphic, anthers short, probably O. capillifolia subsp. capillifolia based on habit and short anthers unless I am misinterpreting one of the concepts.

Oenothera hartwegii (Calylophus hartwegii) - Buds mostly rounded, sepal margins not keeled. Plants perennial; vestiture various: if ovaries grey from dense covering of hairs, hairs throughout plant spreading. Widespread.

Oenothera hartwegii subsp. fendleri (Calylophus hartwegii var. fendleri) - Plants glabrous. Northern High Plains region and Trans-Pecos mountains.

Oenothera hartwegii subsp. filifolia (Calylophus hartwegii var. filifolia) - Plants with glandular hairs; leaves filiform to narrowly lanceolate. Mostly restricted to gypsum or alkali soils, sometimes limestone.

Oenothera hartwegii subsp. hartwegii (Calylophus hartwegii var. hartwegii) - Plants various with sparse glandular hairs and non-glandular hairs; leaves linear to narrowly lanceolate. Primarily stabalized sands and calcareous outcrops.

Oenothera hartwegii subsp. pubescens (Calylophus hartwegii var. pubescens) - Plants generally densely hairy with spreading hairs; leaf bases abruptly truncate. Primarily calcareous outcrops, most prominent subspecies around Lubbock and north.

Oenothera lavandulifolia (Calylophus lavandulifolia) - Buds mostly rounded, sepal margins not keeled. Plants perennial, not viscid; ovaries densely grey hairy with appressed hairs. Widespread, but most prominent in rocky calcareous soils along breaks and draws.

Oenothera tubicula (Calylophus tubicula) - Buds mostly rounded, sepal margins not keeled. Plants annual, viscid from abundance of glandular hairs. Mostly in counties south of Andrews Co. in limestone or other calcareous soils.

Sect. Gaura

Oenothera calcicola (Gaura calcicola) - Plants essentially glabrous, not rhizomatous; flowers medium; fruits with long stipe. Seems to prefer limestone. Illustration of fruit.
Representative observations: flowers, leaves; fruits, plant

Oenothera cinerea subsp. cinerea (Gaura cinerea) - Plants densely hairy, usually with appressed hairs, but may be unappressed; flowers medium; fruits with long stipe. Plants of sandy soils. Illustration of fruit.
Representative observations: rosette and leaf hairs; flowers, fruits, habit, and leaf hairs

Oenothera curtiflora (Gaura parviflora) - Plants densely hairy with soft, villous hairs; flowers very small; fruits without a long stipe, not deeply lobed, not significantly larger at the base. Plants of disturbed, primarily wet soils including waste places and roadsides. Illustration of fruit.
Representative observations: most characteristics; rosette; flowers and fruits

Oenothera lindheimeri (Gaura lindheimeri) - Plants essentially glabrous; flowers large; fruits without long stipe, not significantly enlarged at the base, widest point toward the middle. E TX; commonly cultivated. Illustration of fruit.

Oenothera neallyi (Gaura suffulta var. neallyi) - Plants with sparse, long, straight hairs below inflorescence, glandular hairs above inflorescence; flowers large; fruits without stipe, greatly lobed and enlarged at the base. Mostly Trans-Pecos TX; may occur in southern Llano Estacado. Illustration of fruit.

Oenothera sinuosa (Gaura sinuata) - Plants essentially glabrous, rhizomatous; flowers medium; fruits with long stipe. Most of TX, possibly eastern Llano Estacado. Illustration of fruit.
Representative observations: habit

Oenothera suffrutescens (Gaura coccinea) - Plants usually with many gray, appressed hairs, rhizomatous; flowers medium or slightly smaller; fruits with thickened stipe, widest at base. Common and widespread in various habitats and soils. Illustration of fruit.
Representative observations: rosette; leaves and stem hairs; flowers, fruit, and mature habit

Oenothera suffulta (Gaura suffulta) - Plants with sparse, long, straight hairs below inflorescence, glabrous above inflorescence; flowers large; fruits without stipe, greatly lobed and enlarged at the base. Common in various disturbed soils including roadsides. Illustration of fruit.
Representative observations: rosette; habit; flowers, mature fruit

Oenothera triangulata (Gaura triangulata) - Plants with sparse, long, straight hairs below inflorescence, glabrous above inflorescence; flowers appear medium, most flowers 3-merous (3 petals, sepals, and stigmas; 6 stamens) instead of the usual 4-merous; fruits without stipe, greatly lobed and enlarged at the base. Rolling and Lubbock area of High Plains. Illustration of fruit. Representative observations: flower.

Oenothera xenogaura (Gaura drummondii) - Plants densely appressed hairy, rhizomatous; fruits without or with very short stipe, greatly lobed and enlarged at the base. Most TX except High Plains and Trans-Pecos, likely not on Llano Estacado. Illustration of fruit.

Other species of Texas:

Oenothera arida (Gaura macrocarpa) - Restricted to the Trans-Pecos. Illustration of fruit.
Oenothera boquillensis (Gaura boquillensis) - Restricted to the Trans-Pecos along Rio Grande. Illustration of fruit.
Oenothera cinerea var. parksii (Gaura cinerea) - Illustration of fruit.
Oenothera demareei (Gaura demareei) - Far E TX. Illustration of fruit.
Oenothera filiformis (Gaura longiflora) - East and South TX. Illustration of fruit.
Oenothera hexandra var. gracilis (Gaura hexandra var. gracilis) - Trans-Pecos. Illustration of fruit
Oenothera hexandra var. hexandra (Gaura hexandra var. hexandra) - Trans-Pecos; Chinati Peak. Illustration of fruit.
Oenothera mckelveyae (Gaura mckelveyae) - S TX. Illustration of fruit.
Oenothera patriciae (Gaura brachycarpa) - E half to 2/3rds of TX. Illustration of fruit.

Subsect. Stenosiphon

Oenothera glaucifolia (Stenosiphon liniflorus) - Flowers actinomorphic, white. Illustration of fruit.

Oenothera s.s. (multiple sections)

Oenothera albicaulis (Sect. Kleinia) - Caulescent annual, stems spreading; flowers white; fruits cylindroid. Differs from O. engelmannii by many characteristics including: appressed hairs, habit, habitat, and leaf shape (comparison here). Widespread, but not typically denser or rockier soils.

Oenothera caespitosa (Sect. Pachylophus) - Acaulescent perennial; flowers white; fruits __. Guadelupe Mnts and far east NM in Roosevelt (maybe on west edge of Llano?).

Oenothera canescens (Sect. Gauropsis) - Caulescent perennial, stems spreading; flowers pink; fruits ovoid. Mostly playa basins of Lubbock Co. and north.

Oenothera coronipifolia (Sect. Kleinia) - Caulescent perennial, stems upright; flowers white; fruits cylindroid. NM to Roosevelt County (possibly Llano Estacado).

Oenothera coryi (Sect. Megapterium) - Acaulescent perennial; flowers yellow; fruits _. Differs from O. howardii and O. macrocarpa by its linear leaves. Restricted to NE Llano Estacado into Rolling Plains region (rare).

Oenothera elata (Sect. Oenothera) - Caulescent biennial, stems erect; flowers yellow; fruits cylindroid. Compare with O. jamesii and O. rhombipetala. Trans-Pecos, E TX, and one county from NW Edwards Plateau.

Oenothera engelmannii (Sect. Anogra) - Caulescent annual, stems spreading; flowers white; fruits cylindroid. Differs from O. albicaulis by many characteristics including: many long pilose (spreading) hairs, more robust stems, habit, habitat, and leaf shape (comparison here). Sandy soils, especially disturbed dune habitat that was historically stable and adjacent areas; somewhat widespread but especially the southern counties.

Oenothera grandis (Sect. Oenothera) - Caulescent annual, stems spreading; flowers yellow; fruits cylindroid. Differs from O. laciniata by its much larger flowers (to larger than halfdollar-size vs. to quarter-size or smaller). Widespread but particularly likes disturbed, non-clay, non-calcareous soils.

Oenothera heterophylla (Sect. Oenothera) - Syn. O. cordata. Caulescent biennial, stems erect; flowers yellow; fruits cylindroid. Reported for counties a little southeast, likely absent.

Oenothera howardii (Sect. Megapterium) - Acaulescent perennial; flowers yellow; fruits. Differs from O. coryi by its non-linear leaves; differs from O. macrocarpa by being acaulis and having much smaller fruits imbedded in rosettes. Mostly Trans-Pecos, but also reported from Sweetwater area and NE Llano Estacado; may be absent.

Oenothera jamesii (Sect. Oenothera) - Caulescent biennial; flowers yellow; fruits cylindroid. Compare with O. elata and O. rhombipetala. E Llano Estacado.

Oenothera kunthiana (Sect. Leucocoryne) - Caulescent annual, stems spreading; flowers white; fruits clavate with narrow stipe. S Llano Estacado in limestone. Oenothera tetraptera (Sect. Leucocoryne; endemic to South Texas) can be distinguished from O. kunthiana by the following characteristics from Correll and Johnston 1970:
O. tetraptera: "Stigma usually elevated above the anthers; hypanthium 10-30 [mm] long; petals 20-30 mm long"; in Texas, restricted to South Texas
O. kunthiana: "Stigma surrounded by the anthers; hypanthium (5-)20 mm long; petals 10-20 mm long"

Oenothera laciniata (Sect. Oenothera) - Caulescent annual, stems spreading; flowers yellow; fruits cylindroid. Differs from O. grandis by its much smaller flowers (to quarter-size or smaller vs. to larger than halfdollar-size). Disturbed soils, potentially widespread but probably more restricted to urban areas.

Oenothera macrocarpa (Sect. Megapterium) - Caulescent or acaulescent perennial, stems upright; flowers yellow; fruits very large and winged. Lubbock Co. and North.

Oenothera neomexicana (Sect. Anogra) - NM including far SE NM.

Oenothera pallida (Sect. Anogra) - Trans-Pecos and far N TX.

Oenothera rhombipetala (Sect. Oenothera) - Caulescent biennial; flowers yellow; fruits cylindroid. Petals acute. Sandy soils in the southern and eastern counties.

Oenothera speciosa (Sect. Hartmannia) - Caulescent rhizomatous perennial, stems upright; flowers pink or white; fruits clavate with narrow stipe. Probably naturalized through much of the Llano where it is present from cultivated plants; potentially some native in the southernmost counties; found predominantly in riparian areas, especially draws.

Oenothera triloba (Sect. Lavauxia) - Acaulescent annual; flowers yellow. Widespread in calcareous soils.

Oenothera villosa (Sect. Oenothera) - Caulescent biennial; flowers yellow; fruits cylindroid. E and far N TX; probably absent.

Oenothera groups:

Plants acaulescent; flowers white:
Pachylophus
Plants acaulescent (O. macrocarpa often short caulescent); flowers yellow:
Megapterium: Perennials (Information here and here)
Lavauxia: Annuals
Plants caulescent; fruits clavate with narrow stipe (stalk-like structure); flowers white or pink:
Hartmannia: Perennials
Leucocoryne: Annuals
Plants caulescent; fruits ovoid; flowers white or pink:
Paradoxus: Flowers and plants large; hypanthium 40-55 mm long; petals 15-30 mm long
Gauropsis: Flowers and plants small; hypanthium 5-15 mm long; petals 8-12 mm long
Plants caulescent; fruits cylindric; flowers white (fading pink):
Kleinia
Anogra
Plants caulescent; fruits cylindric; flowers yellow:
Oenothera: Two forms, spreading stems & erect stems

Other species of Texas:
Oenothera biennis (Sect. Oenothera) - East TX and NM mountains.
Oenothera brachycarpa (Sect. Megapterium) - Trans-Pecos.
Oenothera drummondii - Mostly coastal TX.
Oenothera falfurriae - S TX.
Oenothera flava - NM (maybe Trans-Pecos are far N TX?).
Oenothera havardii (Sect. Paradoxus) - Trans-Pecos, N Presidio and Brewster Co.
Oenothera linifolia - East third of TX.
Oenothera mexicana - S TX.
Oenothera pilosella - Far E TX if in TX.
Oenothera primiveris - Trans-Pecos.
Oenothera pubescens - Trans-Pecos.
Oenothera rosea (Sect. Hartmannia) - Trans-Pecos and S TX.
Oenothera spachiana - E third of TX.
Oenothera tetraptera (Sect. Leucocoryne) - S TX.
[From Correll and Johnston 1970: Stigma usually elevated above the anthers; hypanthium 10-30 [mm] long; petals 20-30 mm long
O. kunthiana: Stigma surrounded by the anthers; hypanthium (5-)20 mm long; petals 10-20 mm long]. S TX.
Oenothera texensis (Sect. Hartmannia) - Davis Mountains.

Sources:
A Revision of the Genus Gaura.
Images of Herbarium Specimens of Travis County Plant Species: Family Onagraceae (Plant Resources Center, University of Texas at Austin).
Manual of the Vascular Plants of Texas (Correll and Johnston 1970).
Flowering Plants of Trans-Pecos Texas and Adjacent Areas (Powell and Worthington, 2018).
Taxonomic changes in Oenothera sections Gaura and Calylophus (Onagraceae).
Oenothera gayleana (Oenothera sect. Calylophus, Onagraceae), a new gypsophile from Texas, New Mexico, and Oklahoma .
Shinners and Mahler's Illustrated Flora of North Central Texas.

Sect. Gaura

Oenothera calcicola (Gaura calcicola) - Plants essentially glabrous, not rhizomatous, perennial; flowers medium; fruits with long stipe. Seems to prefer limestone. Illustration of fruit.
Representative observations: flowers, leaves; fruits, plant

Oenothera cinerea var. cinerea (Gaura cinerea) - Plants densely hairy, usually with appressed hairs, but may be unappressed, perennial; flowers medium; fruits with long stipe. Plants of sandy soils. Illustration of fruit.
Representative observations: rosette and leaf hairs; flowers, fruits, habit, and leaf hairs

Oenothera curtiflora (Gaura parviflora) - Plants densely hairy with soft, villous hairs, annual; flowers very small; fruits without a long stipe, not deeply lobed, not significantly larger at the base. Plants of disturbed, primarily wet soils including waste places and roadsides. Illustration of fruit.
Representative observations: most characteristics; rosette; flowers and fruits

Oenothera lindheimeri (Gaura lindheimeri) - Plants essentially glabrous, perennial; flowers large; fruits without long stipe, not significantly enlarged at the base, widest point toward the middle. E TX; commonly cultivated. Illustration of fruit.

Oenothera neallyi (Gaura suffulta var. neallyi) - Plants with sparse, long, straight hairs below inflorescence, glandular hairs above inflorescence, annual; flowers large; fruits without stipe, greatly lobed and enlarged at the base. Mostly Trans-Pecos TX; may occur in southern Llano Estacado. Illustration of fruit.

Oenothera sinuosa (Gaura sinuata) - Plants essentially glabrous, rhizomatous, perennial; flowers medium; fruits with long stipe. Most of TX, possibly eastern Llano Estacado. Illustration of fruit.
Representative observations: habit

Oenothera suffrutescens (Gaura coccinea) - Plants usually with many gray, appressed hairs, rhizomatous, perennial; flowers medium or slightly smaller; fruits with thickened stipe, widest at base. Common and widespread in various habitats and soils. Illustration of fruit.
Representative observations: rosette; leaves and stem hairs; flowers, fruit, and mature habit

Oenothera suffulta (Gaura suffulta) - Plants with sparse, long, straight hairs below inflorescence, glabrous above inflorescence, annual; flowers large; fruits without stipe, greatly lobed and enlarged at the base. Common in various disturbed soils including roadsides. Illustration of fruit.
Representative observations: rosette; habit; flowers, mature fruit

Oenothera triangulata (Gaura triangulata) - Plants with sparse, long, straight hairs below inflorescence, glabrous above inflorescence, annual; flowers appear medium, most flowers 3-merous (3 petals, sepals, and stigmas; 6 stamens) instead of the usual 4-merous; fruits without stipe, greatly lobed and enlarged at the base. Rolling and Lubbock area of High Plains. Illustration of fruit.

Representative observations: flower.

Oenothera xenogaura (Gaura drummondii) - Plants densely appressed hairy, rhizomatous, perennial; fruits without or with very short stipe, greatly lobed and enlarged at the base. Most TX except High Plains and Trans-Pecos, likely not on Llano Estacado. Illustration of fruit.

Here is some information on the Abutilon species of the Llano Estacado.
BONAP

Abutilon fruticosum - Plants perennial; stems strictly upright; leaves gray, ovate, and dentate; mericarps 6-9. Primarily the eastern edge of the Llano Estacado.

Abutilon parvulum - Plants perennial; stems trailing or decumbent; leaves ovate, green, and coarsly dentate; mericarps 5. Relitively widespread in rocky limestone.

Abutilon theophrasti - Plants tall annual; stems strictly upright; leaves grayish, broadly ovate to suborbicular, and dentate; mericarps usually more than 10. Reported from Lynn Co. TX and Lea Co. NM.

Compared to the other US species A. wrightii and A. malacum occur relatively near the southwestern edge of the Llano but have not been documented in the region. Abutilon wrightii may occur in the limestone of the far SW edge around Ector, Winkler, and Andrews counties but further investigation is needed to confirm this.

Identification information taken from Manual of the Vascular Plants of Texas (Correll and Johnston 1970) and Flowering Plants of Trans-Pecos Texas and Adjacent Areas (Powell and Worthington, 2018).

Woo hoo!
Thanks to all our wonderful participants for helping disprove the notion that "There's nothing there"

I should have done this ages ago. I chose Oenothera canescens, a real beauty. This playa species can't be found downstate, so up here on the Llano we're rather proud of it

What a great summer! We're now at 440 species for the Llano. That makes an average of 44 species added per month since the humble beginning of this project just last October. A new species every day, and THEN SOME. You've really put us on the observation map -- my eternal thanks!

Nathan Taylor has prepared a guide, specific to this region, for these interesting little spurges. The photos are marvelous. Check it out, it will surely cause you to notice something that most of us overlook!
http://www.inaturalist.org/guides/2351