Lupinus cruckshanksii Hook.
Common Name: Pearl Lupin
Pearl lupin is an erect annual plant growing from 50 - 250cm tall.
The plant is cultivated in Tropical and Sub-tropical zones for its edible seed, there are many named varieties. It is sometimes grown as an ornamental[
The seed of many lupin species contain bitter-tasting toxic alkaloids, though there are often sweet varieties within that species that are completely wholesome[
]. Taste is a very clear indicator. These toxic alkaloids can be leeched out of the seed by soaking it overnight and discarding the soak water. It may also be necessary to change the water once during cooking. Fungal toxins also readily invade the crushed seed and can cause chronic illness[
S. America - Colombia.
Found in the Andes[
|Other Uses Rating||
|Cultivation Status||Cultivated, Ornamental
A plant of higher elevations up to 4,000 metres in the tropics. It can also be cultivated in the subtropics and temperate zones so long as there is a sufficiently long growing season[
]. It grows best in areas where annual daytime temperatures are within the range 18 - 24°c, but can tolerate 6 - 30°c[
]. Mature plants can survive temperatures down to about -5°c[
]. Mature plants tolerate frost[
]. This has not been our experience, although they tolerate light frosts, the plants are killed by heavy or prolonged frosts[
]. It prefers a mean annual rainfall in the range 500 - 1,000mm, but tolerates 350 - 1,700mm[
An easily grown plant, succeeding in any moderately good soil in a sunny position[
]. Requires an acid to neutral soil[
]. This species might be intolerant of lime[
]. Succeeds on poor soils, its taproot breaking up the sub-soil[
]. Grows best in a sunny position[
]. Succeeds in a range of well-drained soils[
]. Prefers a pH in the range 5 - 6.5, tolerating 4.5 - 7[
]. Once established, it is a very drought tolerant plant[
The seed of most forms contains bitter alkaloids that need to be leached out before the seed can be eaten, however there are some forms that have sweet alkaloid-free seeds[
]. This species has excellent potential as a food crop. It is day-length neutral, flowering and fruiting well at most latitudes[
]. The plants flower and ripen seed continuously until killed by cold weather, making mechanical harvesting difficult[
]. Plants take from 5 - 11 months to fully ripen their crop[
Yields of the mature seeds vary widely, from as little as 290 kilos per hectare in parts of Africa to up to 4.5 tonnes in Australia, whilst yields as high as 7 tonnes have been recorded[
The genes for low-alkaloid types are recessive so they have to be grown separated from other forms if the strains are to be kept pure[
]. It is also probable that plants will hybridize with other species in this genus[
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[
]. When removing plant remains at the end of the growing season, it is best to only remove the aerial parts of the plant, leaving the roots in the ground to decay and release their nitrogen.
Seed - cooked[
]. Used as a protein-rich vegetable or savoury dish in any of the ways that cooked beans are used. The seed can also be ground into a meal and then used with cereal flours in making bread etc[
]. The seed contains up to 50% protein that is rich in lysine and cystine but very low in methionine[
]. If the seed is bitter this is due to the presence of toxic alkaloids, these alkaloids can usually be removed by soaking the seed overnight and discarding the water[
]. Another report suggests that the seed needs to be soaked for 2 - 3 days in order to leech out the alkaloids[
An edible oil is obtained from the seed[
]. It is relatively rich in unsaturated fatty acids, including the nutritionally essential linoleic acid[
An excellent green manure crop, it is able to fix as much as 400kg of atmospheric nitrogen per hectare[
Seed yields up to 18% of an edible oil with uses similar to Soya oil (Glycine soya)[
]. Soya oil has a very wide range of applications and is commonly used in the chemical industry[
]. It is also used in making soap, plastics, paints etc[
The water in which the seeds have been cooked can be used to control pests and diseases[
Pre-soak the seed for 24 hours in warm water and sow in mid spring in situ[
]. You may need to protect the seed from mice. Germination should take place within 2 weeks.
The seed can also be sown in situ as late as early summer as a green manure crop.