For the amateur, lupines are not easy to identify with certainty. Not only is there great variation within individual species, including many named varieties, but that variation results in significant overlap in appearance across species. All bear palmate leaves and stalks of pea-like blooms in mostly — but not always — shades of blue and purple. Many can only be identified through dissection of the blooms to determine, for example, whether a particular internal appendage is fuzzy, lobed, or excessively curved. For those not interested in destroying the nature they’ve set out to admire, a definite identification may not be an option. However, close examination of a specimen’s form, habitat, and location — as well as that of other similar species — can winnow the potential candidates to a reasonably certain match.
And so it is with the broadleaf lupine (Lupinus latifolius). It blooms in the usual lupine range of lavender to medium blue, although sometimes in shades paling to pure white. Blooms arrive in late spring through mid-summer, depending on elevation, in relatively loose racemes1A raceme is an unbranched flower cluster. with individual flowers scattered along the stem or occurring in whorls. Like nearly all lupines, the upright banner petal on each flower sports a large, white spot, which creates a vivid contrast on petals of an otherwise deeper color, but softens the overall shade of lighter-colored varieties. As with most lupines, the white spot turns reddish purple after pollination, which is thought to signal pollinators to go elsewhere. Fuzzy pods soon form. These dry and pop open to release large, pea-like seeds.
The broadleaf lupine derives both its common and species names from its leaflets that are often wider and more teardrop-shaped than the narrower leaflets of other lupines. (“Broadleaf” is a literal translation of the Latin species name “latifolius.”) Although the lower leaf surfaces are moderately hairy, the upper leaf surface is generally smooth, rendering the plant bright green in appearance and not silvery, as with other species with more downy leaves. The leaves typically consist of ten or fewer leaflets.
Broadleaf lupine is a perennial that forms clumps of several unbranched stems that spring each year from a woody rootstock, or, caudex, that persists from year to year and is capable of surviving fire. The caudex, in turn, rises from an extensive root system that can generate new plants asexually from broken bits. The roots also harbor bacteria that convert nitrogen from the air into a form usable by the lupine and other plants. Perhaps not surprisingly then, it prefers gravelly, quick-draining soil typical of the Cascades’ forested slopes. Broadleaf lupine is also shade tolerant, which results in its sometimes open, sprawling habit. This combination of features enables broadleaf lupine to thrive in poor conditions, rendering it both a successional pioneer species in disturbed areas and an apex species in other habitats, particularly in subalpine meadows.
Broadleaf lupines range from Alaska south to Baja California and east into Utah and New Mexico. The greatest diversity in varieties occurs in the south of its range, with only two varieties common in Washington, var. latifolius and var. subalpinus. Although both varieties are scattered across the state, they appear concentrated throughout the Cascade and Olympic mountains. The usually lavender var. latifolius appears more common at low to mid elevations, whereas the electric blue var. subalpinus, also called the subalpine lupine, is more common at higher elevations. (To complicate identification further, var. subalpinus is sometimes classified as a variety of the arctic lupine, L. arcticus, which, as its names imply, has a range that extends much farther north than that of L. latifolius.)
While the broadleaf lupine’s varied forms can render identification challenging, the process of elimination to determine what it is not is useful. Key features distinguish it from the other species that commonly share its range. It is generally smaller and more delicate than the bigleaf lupine (L. polyphyllus), which bears robust, densely packed columns of blooms in a wider range of shades from deep blue to rose pink and commonly features leaves that are larger overall and consist of more leaflets per leaf (often more than ten — hence its Latinized Greek species name, “polyphyllus,” or, “many leaf”). The bigleaf lupine’s leaflets are also more sharply pointed than the broadleaf lupine’s typically rounded leaflets. The bigleaf lupine is also concentrated east of the Cascade Crest. Unlike the broadleaf lupine, both leaf surfaces of the Pacific lupine (L. lepidus) are covered with a long, silvery down, and, although it can reach the same proportions as the broadleaf lupine at lower elevation, it is easily distinguishable at high elevation, where it not only grows beyond the range of the broadleaf lupine but also reduces to a matted ground cover. The Pacific lupine also tends to favor the east slopes of the Cascades and Olympics and the southeast Puget Sound coast. The quite similar riverbank lupine (L. rivularis) is mostly restricted to the edges of coastal and Columbia Gorge waterways with little overlap in range with the broadleaf lupine that prefers higher elevation woodlands and meadows. Most other western Washington lupines are similarly distinguished from the broadleaf lupine by characteristics such as downy foliage, significantly different form or flower color (e.g., yellow or rose), preference for lower elevation and coastal habitats, etc. By close examination of attributes, habitats, and distribution, the amateur botanist can often eliminate most candidate species and arrive at a reasonably certain identification of the broadleaf lupine, especially on the west slopes of the Cascades. (Of course, a “reasonably certain identification” should not be relied upon to determine fitness for consumption, scholarly publication, or other formal usage. All lupines featured on this page were identified by this method, subject to ongoing review and feedback.)
Typical high elevation habitat of broadleaf lupine, var. subalpinus:
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