Lobelia laxiflora Kunth, Nov. Gen. Sp. (quarto ed.) 3: 311. 1819 ["1818"] sec. Rzedowski 2019
- =Lobelia persicifolia Cav., Icon. 6: 12. 1800, nom. illeg. syn. sec. Rzedowski 2019
- =Lobelia cavanillesiana Roem. & Schult., Syst. Veg. 5: 43. 1819 syn. sec. Rzedowski 2019
- =Lobelia fissa Willd. ex Schult., Syst. Veg. 5: 57. 1819 syn. sec. Govaerts 2013
- =Lobelia laxiflora Kunth var. laxiflora, Nov. Gen. Sp. (quarto ed.) 3: 311. 1819 ["1818"] syn. sec. ???
- =Lobelia rigidula Kunth, Nov. Gen. Sp. (quarto ed.) 3: 311. 1819 ["1818"] syn. sec. Govaerts 2013
- =Lobelia cavanillesii Mart., Ausw. Merkw. Pfl. 2: 12, t. 9. 1830 syn. sec. ???
- =Rapuntium cavanillesianum (Schult.) C. Presl, Prodr. Monogr. Lobel.: 27. 1836 syn. sec. Govaerts 2013
- =Rapuntium haenkeanum C. Presl, Prodr. Monogr. Lobel.: 26. 1836 syn. sec. Govaerts 2013
- =Rapuntium laxiflorum (Kunth) C. Presl, Prodr. Monogr. Lobel.: 26. 1836 syn. sec. The Plant List 2013
- =Rapuntium rigidulum (Kunth) C. Presl, Prodr. Monogr. Lobel.: 26. 1836 syn. sec. Govaerts 2013
- =Lobelia haenkeana (C. Presl) A.DC., Prodr. 7: 382. 1839 syn. sec. Govaerts 2013
- =Lobelia concolor M. Martens & Galeotti in Bull. Acad. Roy. Sci. Bruxelles 9(2): 46. 1842, nom. illeg. syn. sec. Rzedowski 2019
- =Siphocampylus mollis Regel in Flora 33: 353. 1850, nom. illeg. syn. sec. ???
- =Siphocampylus warszewiczii (Regel) Regel in Schweiz. Z. Gartenbau 1850: 131. 1850 syn. sec. ???
- =Tupa costaricana Planch. & Oerst. in Vidensk. Meddel. Dansk Naturhist. Foren. Kjøbenhavn 1857: 154-155. 1857 syn. sec. Govaerts 2013
- =Tupa costaricana var. patula Planch. & Oerst. in Vidensk. Meddel. Dansk Naturhist. Foren. Kjøbenhavn 1857: 155. 1857 syn. sec. ???
- =Tupa costaricana var. stricta Planch. & Oerst. in Vidensk. Meddel. Dansk Naturhist. Foren. Kjøbenhavn 1857: 155. 1857 syn. sec. ???
- =Tupa laxiflora (Kunth) Planch. & Oerst. in Vidensk. Meddel. Dansk Naturhist. Foren. Kjobenhavn 1857: 154. 1857 syn. sec. The Plant List 2013
- =Lobelia patzquarensis Sessé & Moc., Pl. Nov. Hisp.: 152. 1890 syn. sec. Rzedowski 2019
- =Lobelia nelsonii Fernald in Proc. Amer. Acad. Arts 36: 503. 1901 syn. sec. Govaerts 2013
- =Lobelia loretensis M.E. Jones in Contr. W. Bot. 18: 68. 1933 syn. sec. Govaerts 2013
- =Lobelia costaricana E. Wimm. in Repert. Spec. Nov. Regni Veg. 38: 85. 1935 syn. sec. ???
- =Lobelia costaricana var. magna E. Wimm. in Repert. Spec. Nov. Regni Veg. 38: 85. 1935 syn. sec. ???
- =Lobelia rensonii E. Wimm. in Repert. Spec. Nov. Regni Veg. 38: 85. 1935 syn. sec. Govaerts 2013
- =Lobelia laxiflora var. stricta (Planch. & Oerst.) McVaugh, N. Amer. Fl. 32A: 96. 1943 syn. sec. ???
- =Lobelia laxiflora f. lutea Standl. & Steyerm. in Publ. Field Mus. Nat. Hist., Bot. Ser. 23: 98. 1944 syn. sec. ???
- =Lobelia laxiflora var. patula (Planch. & Oerst.) E. Wimm., Pflanzenr. IV, 276b: 683. 1953 syn. sec. ???