Dove Lupine

Dove lupine (Lupinus bicolor) is a small lupine, less than a foot in height and easily overlooked unless you are lucky enough to spot a “flock”. It often colonizes burned and other disturbed areas. Scattered individuals can be found along the Rios trail, often near its larger relative, the collared lupine.

The genus name comes from the Latin “Lupinus” meaning wolf, apparently under the mistaken belief that lupines steal nutrients from the soil. In fact, like other members of the pea family, lupines enrich the soil with nitrogen.

Description ^{4,11,23,59,292}

Dove lupine is a diminutive annual lupine from a taproot that stands or spreads four to 16 inches (10-40 cm) and is often obscured by surrounding vegetation. The leaves are up to 1¼ inches across, on petioles of similar length. Leaves are palmately compound with 5-9 leaflets that are tapered and rounded on the end (not truncated like those of our other lupine, collared lupine, L. truncatus). The leaflets are often folded up along the midrib. All parts of the plant are more or less covered with soft hairs.

Flowers occur along terminal spikes, little taller than the surrounding foliage. Although they are generally described as having several whorls (or pseudo-whorls) of four to five flowers, ours are generally smaller, consisting of three or fewer whorls. A flower is small, reported to be less than ½ inch (1 cm) in length; ours are barely ¼ inch (0.5 cm). The small calyx is green, tipped with red-brown, two-lipped, the upper lip with two deep teeth, the lower lip with three smaller teeth. Flowers have the shape typical of a pea flower (papilionaceous): bilaterally symmetrical with one large petal (the banner) held upright, two lateral petals (the wings) directed forward and enclosing two smaller petals (the keel) which, in turn, encloses the pistil and stamens. The banner is obovate, keeled on the upper edge, which produces a groove dividing the lower surface. The banner is white with blue around the edge and a pattern of dark purple spots in the center. The banner may become reddish on older flowers,^23,34,292 but this is not as conspicuous as it is with some other lupines (e.g. collared lupine). The two wing petals are weakly fused along lower margins, mostly blue-violet on the exposed surfaces. The obscured keel petals are whitish with purple tips. Flowers of all white or pink have been reported in the literature.⁴ The pistil has a superior ovary with a simple style and a small domed stigma, occasionally visible projecting from the keel and wings. There are ten stamens fused into a column by the filaments. Dove lupine generally blooms between March and June.¹

Fruit are typical pea pods. When dry, the two valves twist apart, releasing several small seeds.

Classification ^2,44,143

Dove lupine is a dicot angiosperm in the pea family (Fabaceae, formerly Leguminosae), the third largest family of flowering plants in the world. Members of the pea family are characterized by their distinctive flower (papilionaceous) in which five petals are arranged into a bilateral arrangement of one banner, two wings, and a keel. Fruit is a one-chambered pod that has the seeds anchored along one side and that splits open on maturity. Leaves are often compound. Members of the pea family often harbor nitrogen-fixing bacteria in special root nodules.

The pea family is one of the most economically important families ⁴⁴ and contains many well-known plants including garden flowers such as sweet pea, wisteria and acacia, and vegetables such as beans, peanuts, and soybeans. In agriculture, plants are used for forage (e.g. alfalfa)  and as cover crops to restore nitrogen-depleted soils (e.g. field peas and clovers ⁴¹). Some members of the pea family are toxic (e.g. locoweed and lupine ²⁰⁹). “It is possible to poison yourself with members of this family, but it takes some effort.”¹⁴³

Twenty-seven members of the pea family have been reported in the Reserve, many of them non-native species. Common native relatives include ocean locoweed (Astragalus trichopodus), deerweed (Acmispon glaber) and chaparral sweet pea (Lathyrus latiflorus). There is one other lupine, collared lupine (L. truncatus).⁴⁸

Dove lupine is a widespread, variable taxon. In the past, the species currently recognized as L. bicolor has been categorized as several separate species and varieties. For such a small plant, it has amassed a surprising number of synonyms.^2,7

Ecology ^41,292

Dove lupine – with a little help from bacteria – is a “nitrogen-fixer.”

All living things need nitrogen. It is an essential component of proteins, including many enzymes, nucleic acids (DNA and RNA) and the energy transfer molecule ATP. Although the earth’s atmosphere is 80% nitrogen, the form of that nitrogen – molecular nitrogen (N2) – is unavailable for most organisms: they cannot convert it to either organic matter or energy. The few exceptions to this are a diverse group of bacteria and archaea. These have the ability to convert atmospheric N2 to ammonium (NH4+) which is available to them and, ultimately, to other organisms.

Many species in the pea family, including dove lupine, have developed a symbiotic relationship with nitrogen-fixing bacteria, called rhizobia. Rhizobia occur naturally in the soil but only fix nitrogen when they are paired with a host plant.

When rhizobia penetrate the roots of a lupine they stimulate the formation of specialized root structures, nodules enclosing the rhizobia. The plant supplies the bacteria with carbon and energy sources and, in exchange, receive usable nitrogen as ammonium or amino acids. When the lupine dies, its organic material is broken down and the nitrogen is made available to other organisms.

Human Uses

The seeds of some lupine have been cultivated and eaten for centuries.⁴¹ The seeds of other species, however, contain toxic alkaloids and are to be avoided.³¹⁰ The edibility of dove lupine seeds is uncertain, but one report states they are toxic if eaten in large amounts.²⁹² At least one Native American tribe in California, the Miwok of north-central California, used the leaves of dove lupine as a vegetable.⁷⁵

Because of its soil-enriching characteristic, dove lupine is recommended for revegetation areas and general soil rebuilding.¹⁶⁹

Interesting Facts

The seeds of dove lupine are eaten by ground-foraging birds, “especially doves”.²⁹² Perhaps this explains its common name.

The genus name comes from the Latin “Lupinus” meaning wolf,²¹ apparently under the mistaken belief that lupines steal nutrients from the soil. In fact, like other members of the pea family, lupines enrich the soil with nitrogen.