Lupinus perennis
sundial lupine
erect, unbranched or sparsely branched distally, usually hollow.
cauline;
stipules 4–12 mm, longer proximally becoming smaller distally;
petiole (2–)5–10(–15) cm;
leaflets 7–11, blades (15–)20–45(–50) × 4–15 mm, abaxial surface appressed to spreading hairy, strigose, adaxial surface green, glabrous.
8–20(–30) cm;
flowers spirally arranged or whorled.
(2.5–)4–9 cm;
bracts tardily deciduous, 3–6 mm.
(3–)5–7(–10) mm.
(8–)12–16 mm;
calyx abaxial lobe slightly 3-dentate, 5–6 mm, adaxial lobe notched, 4–5 mm;
corolla usually blue, sometimes pink or white, banner glabrous abaxially, upper keel margins ciliate.
3–5 cm, villous.
deciduous, petiolate.
5 or 6.
= 48, 96.
Lupinus perennis
Shorter plants with more basal leaves have been recognized as subsp. gracilis; intermediates between the named varieties are abundant. Variety occidentalis was described from Michigan and Wisconsin as differing by its dense pubescence, which is a variable trait.
In the northern part of its range, Lupinus perennis is sympatric with L. polyphyllus and can be differentiated because the latter has more leaflets and a glabrous keel. Lupinus perennis is of conservation concern in some states and is an important host plant for lepidopterans; the federally endangered Karner Blue butterfly relies on L. perennis as a larval host plant and sundial lupine also is a larval host plant for Frosted Elfin (Callophrys irus) and Wild Indigo Duskywing (Erynnis baptisiae) butterflies and several species of moths.
Lupinus perennis is toxic and potentially fatal to livestock, due to the alkaloid D-lupaine (M. Wink et al. 1995).
Lupinus gracilis Nuttall (1834, not Kunth 1824) is an illegitimate name that pertains here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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