Peter White describes this hard working green manure crop.
Agricultural lupins are a multi purpose annual plant of the pea family related to the ornamental flowers. Lupins (often spelt lupine in the USA) are probably of Egyptian or East Mediterranean origin, and have been cultivated since the days of the ancient Egyptians.
There are various agricultural varieties around: blue lupins (Lupinus angustifolia or L micranthus), white lupins (Lupinus albus) and yellow lupins. For the purpose of soil improvement it’s a case of using whichever you can obtain. Formerly they were much planted in Europe and the sandy areas of eastern England. They are still used today and appear from time to time in the farming press as a novel oil and fodder crop alternative to rape and flax, and to provide flour for foodstuffs (there are now many special varieties for this purpose). Less than 4% of global production is currently used for human consumption. However, it has been estimated that around 500,000 tonnes of food containing lupin ingredients is consumed annually in the EU. This is mainly through low inclusion rates of the flour in wheat-based baked goods.
Lupins as a green manure and conditioner for light sandy soils
Lupins are of great potential interest to the vegan organic grower. The foliage is not dense but the long roots fix nitrogen and break up and aerate the ground bringing up nutrients from deep in the soil. They are of special use to those working light sandy soils as they like these conditions and the roots stabilise the topsoil overwinter, helping to prevent rain and wind erosion. Typically, lupins fix 25% more free nitrogen than clovers and 28% more than peas and beans. This is a very hardworking green manure!
Lupins are readily available in large packs from seed suppliers and smaller packs from for example The Organic Gardening Catalogue and Beans and Herbs. Sow the seeds in drills about 1 inch deep and 3 inches apart, with about 6 inches between the drills. They are slow to germinate and greatly prefer light, slightly acid soil, not thriving in most other soils.
They can be planted from March to July. An early summer sowing can be cut down before flowering (compost the foliage or use as mulch) then leave the roots undisturbed until a few weeks before planting time, when a light cultivation of the top few inches should leave a stable nitrogen-rich bed. The amount of pre-sowing cultivation you do depends on your soil type and feelings about tillage; lupins are not difficult to dig in.
If you wish, don’t cut down all the plants before flowering. Leave a few at the end of the patch to produce a profusion of beautiful blue flowers, which are attractive to insects. After flowering you can save the seeds for next year when the pods have dried on the plant. Lupins do cross-pollinate readily so saved seeds may not be true to the original plant.
It’s possible to sow lupins as an intercrop, for example among sprouts or cabbages, or between rows of potatoes, where they will contribute nitrogen.
Lupins will also help in growing trees on light soils. They can be used before planting young trees, to stabilise the land. Add organic matter and add nitrogen; also planting them along rows of established trees will add nitrogen and be some help with weed suppression.
Multi talented lupins
Lupins are multipurpose plants, rivalling hemp for versatility. In 1917 a ‘lupin’ banquet was given in Hamburg at a botanical gathering, at which a German Professor, Dr. Thoms, demonstrated the multifarious uses to which the lupin might be put. At a table covered with a tablecloth of lupin fibre, lupin soup was served. After the soup came lupin “beefsteak”, roasted in lupin oil and seasoned with lupin extract, then bread containing 20% of lupin, lupin margarine and “cheese” of lupin albumen, and finally lupin liqueur and lupin coffee. Lupin soap served for washing the hands, while lupin-fibre paper and envelopes with lupin adhesive were available for writing.
The lupin was cultivated by the Romans as an article of food. Pliny says: ‘No kind of fodder is more wholesome and light of digestion than the White Lupine, when eaten dry. If taken commonly at meals, it will contribute a fresh colour and a cheerful countenance.’ The yellow legume seeds, commonly called Lupini beans, were popular with the Romans and they spread the cultivation of them throughout the Roman Empire. Were lupini beans sold in the Collosseum like peanuts are today at sports venues? Very likely!
Lupin flour occasionally turns up these days in speciality bread and cakes and the seed is used in a variety of foods, including many vegan-friendly items. Eating your own lupins is not however suggested as depending on type and growing conditions (you will not know which cultivar you are growing) an alkloid or mycotoxic poison can be present. Commercial growers know how to contend with this but home growers should leave the lupins for the soil, not the dinner plate! As a ‘new’ food, lupin is now being treated with caution because such foods have potential to cause allergies.
This article appeared in Growing Green International magazine Num 9 (Summer 2002), p7, but compared to the original article, it has been updated by the author.