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Lupinus angustifolius is a species of lupin known by many common names, including narrow-leafed lupin and blue lupin. L.angustifolius L. 1753, Sp. Pl:721; Willd. 1803, l. c.:1024; DC. 1825, l. c.:407; Boiss. 1872, l. c.:28; Willk. et Lange, 1880, l. c.:466; Halacsy, 1901, l. c.:340; Aschers. et Graebn. 1907, Syn. Mitteleur. Fl. 6 (2):231; Fiori, 1925, l. c.:804; Plitmann, 1966, Israel J. Bot. 15:26; Chamberlain in Davis, 1970, l. c.:39; Zohary, 1972, l. c.:43, t. 57; Gladstones, 1974, l. c.:9; Vass. 1987, in Fl. Part. Eur. URSS, 6:214. – L. linifolius Roth, 1787, Bot. Abh. 14, t. 5. - L. reticulatus Desv. 1835, Ann. Sc. Nat. ser. 2,3:100. - L. leucospermus Boiss. 1849, Diagn. Pl. Or. Nov. 9:8. - L. philistaeus Boiss. 1849, l.c.: 9. – L. angustifolius var. sativus et var.spontaneus Libk. 1931, Lupinus :53. - L.opsianthus Atab. et Maiss., 1968, Bjull. Glav. Bot. Sad. Acad. Nauk SSSR. : 75. - L. angustifolius subsp.angustifolius et subsp. reticulatus (Desv). Franco et Silva, 1968, in Fl. Europ. 2:105. – narrow-leafed or blue lupin.
Typus: Herb. Linn. No 898-7 (LINN).
Occurs on meadows, among rocks, in bushes, on seaside sands and near reservoirs, along the roads and, as a weed, in the field. Tends to grow on well-ventilated soils. It is widespread in all Mediterranean countries and also in Asia Minor, Transcaucasia and Iran. Naturalized in Southern Africa and Southwest Australia. Widely cultivated in Northern Europe (Germany, Holland, Poland, CIS), in the southeast part of USA and in New Zealand. It is a rather polymorphic species. The variability of characters depends on eco-geographic conditions. Wild-growing races have, as a rule, narrow pods, smaller-sized leaflets and seeds, while the plants are not so tall. The size of seeds and their colouring vary over all the area of growing. Large-seeded plants usually occur closer to arable soils, while small-seeded ones are found on inshore sands and slopes. The color of seeds varies from dark grey (almost black) with light spots and specks of miscellaneous size, grayish-brown and brown to light grey or white. Seeds with colored testa usually correlate with cyan and pink flowers. In these two characters (traits) homologous variability is observed. Unpigmented (white) seeds are typical for white-flowered and lilac plants. These combinations of characters do not demonstrate any geographic arrangement. There is no abrupt gap between cultivated and wild forms. On the contrary, transition between them appears very smooth. Therefore there is nothing to justify the existence of two species (L. linifolius Roth. and L. opsianthus Atab. et Mais.) as well as two subspecies (subsp. angustifolius and subsp. reticulatus (Desv.) Franko et Silva.) differing only in the width of leaflets and the size of seeds (quantitative characters). In our opinion, it seems more correct to subdivide this species in a different way. Using the developed criteria of intraspecific taxa, VIR’s blue lupin collection was screened to identify 13 varieties of L. angustifolius L. distinctly differing from each other in the color of seeds and the corolla. Variations in the color of cotyledons, vegetative parts and carina have been used for identification of 12 subvarieties. Besides, the plants with determined branching and fascicular stems are described as 8 separate forms.
Like other legumes, the narrow-leafed lupin fixes nitrogen in a symbiotic interaction with different bacteria in the rhizosphere. Bacteria living in this rhizosphere include Bradyrhizobium lupinii or the newly discovered species Kribbella lupini.
The narrow-leafed lupin is an erect, branching herb sometimes exceeding one meter. There are reduced-branching cultivars. Each palmate leaf is divided into 5 to 9 linear leaflets under 4 centimeters long. The herbage is slightly hairy in some areas. The inflorescence bears many flowers in shades of blue, violet, pink, or white. The fruit is a legume pod containing seeds of varying colors from dark gray to brown to white, or speckled or mottled. Lupinus angustifolius has a high content of alkaloids, e.g. lupanin or angustifolin. However, cultivars with a low alkaloid content have been bred. These low alkaloid cultivars are called sweet lupins.
The narrow-leafed lupin is sown as early as possible in the spring, to have the growing season as long as possible. Another reason for early sowing is its sensitivity to high temperature in spring. Lupins react with a higher yield loss, when they are sown late, than other crops (e.g. cereals) do. The optimum seed density depends on the site yield potential  and is generally higher in non-branching cultivars than in branching ones. The variance is high, 14 to 138 plants per m2  are an optimal plant density, depending on the yield potential of the site. On most grounds, a plant density around 80 plants per m2 would be the optimum.
Lupins are usually sown with technique used for cereals in a depth of about 5 cm.
The narrow-leafed lupin needs to be harvested as soon as the grain reaches a moisture of about 12%. The straw usually isn‘t ripened at this point, but further delay of harvest would increase losses from shattering of the pods and lodging. The harvest is done with machinery used for cereals. Swathing is not widely applied. However, it can be a good alternative to reduce harvest losses in case harvest is delayed.
The disease and weed spectrum of the narrow-leafed lupin is different from most major crops and it is able to improve the soil (see Use). Therefore, it is a valuable partner in intensive crop rotations.
The plant is used as a green manure or as a grain legume for animal feed or human consumption. Through its ability to fix nitrogen and its low nutrient requirement this plant is suitable to be planted on exhausted fields as a soil improver. Additionally, lupins have strong roots, that can reduce the compaction of a soil.
The plant is widely used as a fodder for livestock, due to its high protein and energy content. Lupins contain high levels of fermentable carbohydrates and low levels of starch and are, therefore, an adequate ruminant feed. But lupins are a valuable feed for monogastric animals as well, because of the high digestibility of the lupin nitrogen and the low level of protease inhibitors.
- Kurlovich, B. S. (2002). Lupin Classification. In Lupins. Geography, classification, genetic resources and breeding.
-  Lupinus angustifolius L.(Narow-leafed lupin)
- Trujillo, M. E., et al. (2006). Kribbella lupini sp. nov., isolated from the roots of Lupinus angustifolius. Int J Syst Evol Microbiol 56:407-11.
- FAO, Food and Agriculture Organization of the UN. "Lupinus angustifolius". Retrieved 29 November 2012.
- Eckardt, Thomas; Haag, Franz and Dietrich, Regine (2002). "Der Einfluss von Wuchstyp, Saatzeitpunkt und Saatstärke auf den Kornertrag von Blauen Süsslupinen (Lupinus angustifolius)". Lupinen 2001:Ergebnisse aus Forschung, Anbau und Verwertung.
- Gladstones, J.S.; Atkins, Hamblin. Lupins as crop plants. Wallingford, Oxon, UK: CAB International. p. 304. ISBN 0-85199-224-2.
- Gladstones, J.S.; Atkins, Hamblin. Lupins as crop plants. Wallingford, Oxon, UK: CAB International. p. 303. ISBN 0-85199-224-2.
- Gladstones, J.S.; Atkins, Hamblin. Lupins as crop plants. Wallingford, Oxon, UK: CAB International. pp. 304–307. ISBN 0-85199-224-2.
- French, R.J.; McCarthy, K. and Smart, W.L. (1994). "Optimum plant population densities for lupin (Lupinus angustifolius L.) in the wheatbelt of Western Australia". Australian Journal of Experimental Agriculture 34: 491–497. doi:10.1071/EA9940491.
- Gladstones, J.S.; Atkins, Hamblin. Lupins as crop plants. Wallingford, Oxon, UK: CAB International. p. 320. ISBN 0-85199-224-2.
- Henderson, C.W.L. (1989). "Using a penetrometer to predict the effects of soil compaction on the growth and yield of wheat on uniform sandy soils.". Australian Journal of Agricultural Science 40: 497–5008. doi:10.1071/AR9890497.
- Sujak, Agniesszka; Kotlarz, Anna and Strobel, Waclaw (2006). "Compositional and nutritional evaluation of several lupin seeds". Food Chemistry 98 (4): 711–719. doi:10.1016/j.foodchem.2005.06.036.