Lupins have soft green to grey-green leaves which may be coated in silvery hairs, often densely so. The leaf blades are usually palmately divided into five to 28 leaflets, or reduced to a single leaflet in a few species of the southeastern United States and eastern South America.[4]
The flowers are produced in dense or open whorls on an erect spike, each flower 1–2 centimetres (3⁄8–3⁄4 inch) long. The pea-like flowers have an upper standard, or banner, two lateral wings, and two lower petals fused into a keel. The flower shape has inspired common names such as bluebonnets and quaker bonnets.
The fruit is a pod containing several seeds. The seeds contain alkaloids which lend them a bitter taste.
The genus Lupinus L. and, in particular, its North American species were divided by Sereno Watson (1873) into three sections: Lupinus, Platycarpos, and Lupinnelus. Differences in habitat and in the number of ovules were the basis for this classification. A majority of the perennial and annual species from the American continent described by Watson were referred to Lupinus. Some annual species with two ovules in the ovary and two seeds in the pod (L.densiflorus, L.microcarpus, etc.) were attributed to the Platycarpos section. Section Lupinnelus consisted of one species (L.uncialis), with axillary and solitary flowers, scarcely reflexed banner, and also with two ovules in the ovary.
While Watson's work was predominantly based on study of North American species, the later research of Ascherson and Graebner (1907) extended his principle of classification to cover all lupins from the Eastern and Western Hemispheres, also using number of ovules (seedbuds) in the ovary (and thus of seeds in the pod) as the criterion for this division. They described two subgenera, Eulupinus and Platycarpos. Most of the described species were referred to subgen. A. Eulupinus. Subgen. B. Platycarpos included several annual species from the Eastern Hemisphere with two seedbuds and seeds in the bean (the same species, as the one specified by S. Watson).
A current schema retains this distinction, but uses the nomenclature for the subgenera of Platycarpos and Lupinus. In this schema, subgenus Platycarpos (S.Wats.) Kurl. contains perennial and annual species from the Western Hemisphere, with a minimum two or more ovules or seedbuds. Subgenus Lupinus consists of 12 species from Africa and the Mediterranean, with a minimum of four ovules or seedbuds.[5]
The taxonomy of Lupinus has always been confusing. How many distinct species exist or how they might be organized within the genus is not clear. The plants are variable and the taxa are not always distinct from one another. Some American taxa have been described as complexes rather than separate species.[6] Estimates of the number of lupine species generally fall between 200 and 500.[2] One authority places the estimate at approximately 267 species worldwide.[1] Currently, two subgenera are recognized.
The ovary contains two and more ovules or seedbuds. The seed are predominantly small-sized, with an underdeveloped embryo and small amount of endosperm. Cotyledons are small-sized, with long caulicles. The first pair of true leaves is alternate. The stem is predominantly naked with waxen coating. Dominating is the monopodial type of branching. Leaflets are smooth, with waxen coating or slight pubescence, predominantly narrow. Pods are flat or orbicular, with two or more seeds. Represented by frutcuilose, fruticose and herbaceous perennial forms, or less often annual ones. Plants are cross-pollinated. Chromosome number 2n is either 36, 48, or 96.[7] This subgenus is distributed throughout North, Central and South America, predominantly in the mining systems of the Andes and Cordillera. Some species are cultivated (L.mutabilis, L.polyphyllus). This subgenus includes several hundred species, requiring further analysis of their authenticity.
In its current circumscription,[7] subgenus Lupinus includes 12 species from the Mediterranean region and Africa with at least four ovules or seedbuds in the ovary:
While some sources believe the origin of the name to be in doubt, the Collins Dictionary definition asserts that the word is 14th century in origin, from the Latin lupīnus "wolfish" from lupus "wolf"[41] as it was believed that the plant ravenously exhausted the soil.[42]
But a more likely explanation is that lupinus meant that the plants were as dangerous to livestock as wolves, because the alkaloid poisons of Lupines can sicken or kill grazing animals, especially sheep. Farmers have known since ancient Rome [43] that lupines improve soil by adding nitrogen and loosening compacted earth with their strong root systems, so the Collins explanation is improbable.
Certain species, such as the yellow bush lupin (L. arboreus), are considered invasiveweeds when they appear outside their native ranges. In New Zealand, lupines are viewed as invasive and a severe threat in some cases.[44]L.polyphyllus has escaped into the wild and grows in large numbers along main roads and streams on the South Island. A similar spread of the species has occurred in Sweden, Finland and Norway after the non-native species was first deliberately planted in the landscaping along the main roads.[citation needed] Lupins have been planted in some parts of Australia with a considerably cooler climate, particularly in rural Victoria and New South Wales.
Lupins are important larval food plants for many lepidopterans (butterflies and moths). These include:
Lupinus polyphyllus, the garden lupin, and Lupinus arboreus, the tree lupin, are popular ornamental plants in gardens, and are the source of numerous hybrids and cultivars in a wide range of colours, including bicolors. As legumes, lupins are good companion plants in gardens, increasing the soil nitrogen for vegetables and other plants. As well as growing in the ground, lupins can do well in pots on balconies or patios.[52]
Like other legumes, lupines can fix nitrogen from the atmosphere[53] into ammonia via a rhizobium–root nodulesymbiosis, fertilizing the soil for other plants. This adaptation allows lupins to be tolerant of infertile soils and capable of pioneering change in barren and poor-quality soils. The genus Lupinus is nodulated by Bradyrhizobium soil bacteria.[5]
In the early 20th century, German scientists attempted to cultivate a sweet variety of lupin lacking the bitter taste, making it more suitable for both human and animal consumption.[54]
Many annual species of lupins are used in agriculture and most of them have Mediterranean origin.[55]
While originally cultivated as a green manure or forage, lupins are increasingly grown for their seeds, which can be used as an alternative to soybeans. Sweet (low alkaloid) lupins are highly regarded as a stock feed, particularly for ruminants, but also for pigs and poultry and more recently as an ingredient in aqua-feeds. Three Mediterranean species of lupin, blue (narrow-leafed) lupin, white lupin, and yellow lupin, are widely cultivated for livestock and poultry feed.
The market for lupin seeds for human food is currently small, but researchers believe it has great potential. Lupin seeds are considered "superior" to soybeans in certain applications and evidence is increasing for their potential health benefits. They contain similar protein to soybean, but less fat. As a food source, they are gluten-free and high in dietary fiber, amino acids, and antioxidants, and they are considered to be prebiotic.[citation needed]
Some lupins contain certain secondary compounds, including isoflavones and toxic alkaloids,[53] such as lupinine, anagyrine and sparteine. With early detection, these can be removed through processing, although lupins containing these elements are not usually selected for food-grade products.
A risk of lupin allergy exists in patients allergic to peanuts.[57] Most lupin reactions reported have been in people with peanut allergy.[58] Because of the cross-allergenicity of peanut and lupin, the European Commission, as of 2006, has required that food labels indicate the presence of "lupin and products thereof" in food.[59]
Lupin plants can be colonized by the fungus Diaporthe toxica[60] which can cause a mycotoxicosis known as lupinosis when ingested by grazing animals.
The legume seeds of lupins, commonly called lupin beans, were popular with the Romans, who cultivated the plants throughout the Roman Empire where the lupin is still known in extant Romance languages by names such as lupini.
Seeds of various species of lupins have been used as a food for over 3,000 years around the Mediterranean[61] and for as long as 6,000 years in the Andes.[62] Lupins were also used by many Native American peoples of North America such as the Yavapai. The Andean lupin or tarwi (Lupinus mutabilis) was a widespread food in the Incan Empire; but they have never been accorded the same status as soybeans, dry peas and other pulse crops. The pearl lupin of the Andean highlands of South America, L.mutabilis, known locally as tarwi or chocho, was extensively cultivated, but no conscious genetic improvement other than to select for larger and water-permeable seeds seems to have been made. Users soaked the seed in running water to remove most of the bitter alkaloids and then cooked or toasted the seeds to make them edible,[63][full citation needed] or else boiled and dried them to make kirku,[62] reported as a pre-Columbian practice in Las Relaciones geográficas de Indias.[64] Spanish domination led to a change in the eating habits of the indigenous peoples, and only recently[65] (late 20th century onward) has interest in using lupins as a food been renewed.[66][61]:353
Lupins can be used to make a variety of foods both sweet and savoury, including everyday meals, traditional fermented foods, baked foods, and sauces. The European white lupin (L.albus) beans are commonly sold in a salty solution in jars (like olives and pickles) and can be eaten with or without the skin. Lupini dishes are most commonly found in Europe, especially in Portugal, Spain, Greece, and Italy. They are also common in Brazil and Egypt. In Egypt, the lupin is known in Arabic as ترمسtermes, and is a popular street snack after being treated with several soakings of water, and then brined. In Portugal, Spain, and the Spanish Harlem district of New York, they are consumed with beer and wine. In Lebanon, Palestine, Israel, Jordan, and Syria the salty and chilled lupini beans are called turmus (in Arabic: تُرمُس, Hebrew: תורמוס) and are served as part of an apéritif or a snack. Other species, such as L.albus (white lupin), L.angustifolius (narrow-leafed lupin),[67] and L.hirsutus (blue lupin)[68] also have edible seeds.[69]
Consumed throughout the Mediterranean region and the Andean mountains, lupins were eaten by the early Egyptian and pre-Incan people and were known to Roman agriculturalists for their ability to improve the fertility of soils.[70]
In the late 18th century, lupins were introduced into northern Europe as a means of improving soil quality, and by the 1860s, the garden yellow lupin was seen across the sandy soils of the Baltic coastal plain.
The successful development of lupin varieties with the necessary "sweet gene" paved the way for the greater adoption of lupins across Europe and later Australia.[citation needed]
Further work carried out by the Western Australian Department of Agriculture and Food during the 1950s and '60s led to more sweet lupin crops produced in Western Australia now than anywhere else in the world.[citation needed]
Aïnouche, A. K.; Bayer, R. J. (1999). "Phylogenetic relationships in Lupinus (Fabaceae: Papilionoideae) based on internal transcribed spacer sequences (ITS) of nuclear ribosomal DNA". American Journal of Botany. 86 (4): 590–607. doi:10.2307/2656820. JSTOR2656820. PMID10205079.
Kurlovich, B. S. and A. K. Stankevich. (eds.) Classification of Lupins. In: Lupins: Geography, Classification, Genetic Resources and Breeding. St. Petersburg: Intan. 2002. pp. 42–43. Accessed 2 August 2013.
"ILDIS LegumeWeb entry for Lupinus". International Legume Database & Information Service. Cardiff School of Computer Science & Informatics. Retrieved 11 April 2014.
Tietz, W., & von Minckwitz, M.-C. (2023). Plant Nutrition in the Roman empire. Journal of Plant Nutrition and Soil Science, 186, 479–486. https://doi.org/10.1002/jpln.202300152
Anweiler, G. G. (2007). "Species Details Schinia suetus". University of Alberta Museums. E.H. Strickland Entomological Museum. Retrieved 8 November 2020.
Eastwood, R. J., et al. 2008. Diversity and evolutionary history of lupins—insights from new phylogenies. pp.346–54, In: Palta, J. A. and J. B. Burger. (Eds.) Lupins for Health & Wealth. Proceedings 12th International Lupin Conference, Fremantle, Australia; International Lupin Association, Canterbury, New Zealand.
Putnam, D. H., et al. Lupine. Alternative Field Crops Manual. University of Minnesota, University of Wisconsin Extension. 1997.
Zhukovsky, P.M. 1929. A contribution to the knowledge of genus Lupinus Tourn. Bull. Apll. Bot. Gen. Pl.-Breed., Leningrad-Moscow, XXI, I:16-294.
Kurlovich, B.S. 1989. On the centers of species formation of the genus Lupinus L. (in Russian). Bull.N.I. Vavilov Inst. of plant Industry. Leningrad, 193:20-24.
Kurlovich, B.S., Rep’ev, S.I., Shchelko, L.G., Budanova, V.I., Petrova, M.V., Buravtseva, T.V., Stankevich, A.K., Kartuzova, L.T., Alexandrova, T.G., Teplyakova and T.E., Malysh, L.K. 1995. Theoretical basis of plant breeding. Vol.111. The gene bank and breeding of grain legumes (lupine, vetch, soya, and bean), St.Petersburg, VIR, 438p.
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