Linaria

1. Plant a slender annual with cauline leaves less than 1.7 mm broad; corolla red-pink (at least in the Michigan collection).

L. spartea

1. Plant a sturdy perennial with cauline leaves all or mostly at least (1.5–) 1.7 mm broad; corolla yellow.

2. Leaves ovate, ca. 3 times as long as broad or shorter; corolla (including spur) (23–) 27–40 (–43) mm long.

L. dalmatica

2. Leaves linear, tapered to the base, ca. 10 times as long as broad or longer; corolla (18–) 23–28 (–35) mm long.

L. vulgaris

All species found in Linaria

Linaria dalmaticaDALMATIAN TOADFLAX 
Linaria sparteaBUTTER-AND-EGGS 
Linaria vulgarisBUTTER-AND-EGGS 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. November 22, 2017. http://michiganflora.net/genus.aspx?id=Linaria.