Lupins: planting the protein bomb in your own garden

Lupins have a uniquely beautiful flower. Their seeds are also a protein-rich meat substitute and alternative to soy that can be grown in your own garden.

Lupins (Lupinus) are probably the most colourful representatives of the legumes (Fabaceae) and belong in every cottage garden. They feature captivatingly large flower heads, which are an ideal background planting in the perennial bed. After flowering, the other advantages of the plants appear. The seeds have a high protein content and provide a local alternative to soy. You can also improve any bed by planting lupins, because the plants loosen soils and bind atmospheric nitrogen. In turn, lupins want only a little sun, because otherwise they are extremely frugal in terms of location and care.

Lupins: origin and characteristics

Mostly herbaceous, perennial plants ranging from 0.3 to 1.5 metres in size, they originated in North America. The plant, which now grows wild here, came to Europe at the beginning of the 19th century. In Central Europe, the most common species encountered is the many-leaved lupin (Lupinus polyphyllus). Other important cultivated species include the yellow lupin (Lupinus luteus), white lupin (Lupinus albus), and narrow-leaved lupin (Lupinus angustifolius), which, like many-leaved lupin, flowers blue and, as a cultivated form, also red. Lupins are among the richest sources of vegetable protein. It was used by Saint Hildegard in preparations to cure all kinds of diseases. For example, lupine is said to have anti-cancer, antioxidant and antimicrobial effects. It is also suitable for diets for protein deficiency diseases, diabetes, rheumatism, skin and stomach diseases.

Lupins: distinguishing toxic from non-toxic lupins

Especially in the case of garden and wild lupins, the seeds contain a poisonous bitter substance. The lupinin and spartein it contains can cause respiratory paralysis and even death if consumed. However, since the 1930s there have been certain cultivated forms that do not contain the bitter substance, or only in very small quantities, and are therefore non-toxic. The absence of bitter substances gave them the name sweet lupins. Only for allergy sufferers with a hypersensitivity to legumes can lupins still become a problem. The keyword here is: Peanut allergy. More on the toxicity of lupins is available here.

Lupins as a valuable food

Before we can include lupine seeds in our diet, they have to be processed. Earlier varieties had to be soaked in salt water for 14 days, while the sweet lupin seeds are now soaked for only 1 to 2 days. This removes the last bitter substances. Such pickled seeds are a popular beer snack in establishments in the Mediterranean region. But you can also process the seeds in many ways. This provides interesting alternatives for lactose intolerant, vegan and low carb followers.

• Lupin flour
  Lupins are largely processed into protein flour. The protein content can be up to 40%. This is about four times more than whole wheat flour. The high-water binding makes the flour particularly useful for vegans, as no eggs need to be used in baking. The high antioxidant content makes baked goods last even longer. However, the flour still has a very strong inherent taste, which is why it is recommended to keep the content to about 15-25% during baking. Otherwise, you get a yellowish colour and a nutty flavour.
• Lupin coffee
  The only thing we are talking about here is a substitute for the wonderful taste of coffee, because lupin coffee does not contain caffeine. This means there is no stimulating effect. Instead, the taste brings a slight hint of autumn leaves and almond. To produce it, the seeds are dried and then roasted. Lupin seeds refined in this way have a very strong, harmonious aroma because they are roasted at low temperatures and therefore contain hardly any bitter substances. The beans are ground and prepared like normal coffee beans.
• Lupin yogurt
  Lupin yoghurt provides a creamy alternative for vegans. This is made from lupin milk and is now available in a variety of flavours from natural to raspberry to stracciatella. The consistency is slightly thicker than normal yoghurt.

Lupins as green manure

Planting lupins is great for dressing up harvested or newly planted vegetable beds. Lupins are very hardy and can be sown even after the harvest of the vegetable. They are also a very good nitrogen fertiliser. They enrich the soil with up to 100 kg of nitrogen per hectare. These vast amounts of nitrogen are fixed by a symbiosis between the lupin roots and nodule bacteria (rhizobia). In addition, the roots also penetrate compacted soil. This loosens the soil and makes it more permeable for subsequent crops. Deep-rooting varieties such as yellow lupin (L. luteus), narrow-leaved lupin (Lupinus angustifolius), or white lupin (L. albus) are particularly well suited for this purpose. After winter, annuals are mowed down and the clippings are left as a mulch layer. Once the layer has dried, it is worked into the soil. In this way, the nitrogen gets into the soil and nutrient-rich humus is created. After four weeks, the first new plants can be planted.

Lupins in the garden

Lupins are suitable not only as a vegetable, fodder and wild plant. With flowerheads of up to 50 cm high in white, yellow, blue-violet, pink, orange or multicoloured, they have also found their way into our gardens as ornamental plants. Most variants of the garden lupin (Lupinus polyphyllus) – also called perennial lupin – are available commercially.

Note: Westcountry lupins have impressively intense flower colours.

The perfect location

Especially when it comes to the soil, there is not much to consider when choosing a location. The roots of the lupin are strong and due to their good nitrogen fixation, lupins also grow well on very sandy and lean soils. For these protein-rich plants, the following applies:

• Habitat: Open, sunny and sheltered from the wind
• Soil: Moderately nutritious, well-drained and low in lime

Lupins also accept shadier spots. However, the flowering and the stability of the plants suffer. If the soil is too calcareous (alkaline soil pH), the leaves turn yellow. Waterlogging is also not tolerated.

Planting lupins: step-by-step

Lupins look best planted in small groups in the border. Here they form a brightly coloured background for smaller perennials. The procedure for planting is as follows:

• Planting time: early autumn or spring
• Planting distance: approx. 50 cm
• Planting hole: at least as deep as the root
• Carefully place plant in planting hole
• Fill with soil and press down
• Water well
• Water well the next few days, but avoid waterlogging

If lupins are planted too densely, there is an increased risk of mildew. In addition, lupins have very limited suitability for pot culture because of their deep roots. If you still want to grow lupins in pots, stick to small-growing varieties, use a very tall pot, and be sure to overwinter the plants in a sheltered spot.

Propagation

Lupins are very easy to propagate by division, sowing or cuttings.

Sowing lupin seeds

In places that have already been planted, lupins will seed themselves. In the process, the seeds fly up to six metres. Heavy self-seeding means that lupins can quickly crowd out native wild plants in places, once they settle in. For this reason, the many-leaved lupin (Lupinus polyphyllus) is considered an invasive species in our country. If you do not have any lupins in your garden yet, sow them yourself. In this case, the seeds are sown directly into the bed:

• Sowing time: March – May
• Lightly roughen seeds with sandpaper and soak in water for 24 hours
• Sowing depth: 2 – 3 centimetres

The seeds can also be grown indoors in pots from January. From June, the small lupins then move outdoors. Perennial lupin species can be sown until the end of August if necessary. Whether grown directly into the bed or in a pot, the first flowering does not begin until the following year.

You can find more about lupin seeds here.

Propagating lupins by cuttings

Propagation via cuttings is also very easy. The cuttings, 5 to 10 centimetres long, are cut in the spring. Then proceed as follows:

• Remove all leaves except for the top one or two.
• Fill seedling pots with loose substrate such as expanded clay
• Insert cuttings halfway into the substrate
• Location: Warm and not full sun
• Keep substrate evenly moist
• After rooting (after four to six weeks), place individually in pots with soil.
• Plant out into the bed after another six weeks

Caring for lupin plants

Lupins do not require much attention, because they can take care of themselves quite well. However, they should be rejuvenated about every three years. To do this, dig up the rootstock in the spring and replant the new shoots.

Watering and fertilising

By themselves, once grown, lupins do not require watering because of their very deep roots. If watering is needed after a long dry period or if it has rained heavily, it is worth loosening the soil around these colourful protein bombs. This promotes a long flowering. It also prevents compaction of the soil, which is very beneficial to plants that are sensitive to waterlogging.

The rule with fertilisation is: Less is more. You can over fertilise plants very quickly, increasing the risk of root rot and other diseases and pests. Lupins can supply themselves with nitrogen in particular due to their symbiosis with bacteria. The additional mixing of stone flour or algae lime into the soil further promotes this symbiosis. If you want to strengthen the stems of the plants, some of which grow three metres high, fertilise with a plant-based fertiliser such as our Plantura Flower Food with slow-release effect.

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Pruning lupins

Lupins do not need to be cut into shape. But if the perennials have grown too tall, the flower stems can simply be cut back to the desired height. More important is the cut after flowering. If the flowers are cut back immediately after flowering, this will encourage repeat flowering in the summer. In addition, faded flowers should be removed so that the lupins do not spread uncontrollably in the garden. Diseased leaves should be removed year-around and immediately to prevent the spread of diseases such as mildew. Pruning to above ground level in the autumn is not necessary. On the contrary, the upper part of the plant serves as winter protection for the roots and as green manure for next year.

Caring for lupins in the garden: Summary

• Divide every three years
• Watering: No longer necessary after growing; avoid waterlogging.
• Fertilising: Sensitive to overfertilisation; stone flour or algae lime promote symbiosis with nodule bacteria; bone meal strengthens stems.
• Cutting: Remove flower heads after flowering; remove diseased leaves

How do you harvest lupin seeds?

The pea-like flower heads appear from late May to early August. They form pod fruits that contain several of the coveted seeds. Harvest seeds for consumption only if you are sure about the bitter content. Particularly in the case of crosses that have originated in one’s own garden, it may be that the bitter substances of the sweet lupin varieties that have been bred away come through again in the subsequent generation. There is a high risk of poisoning here. If you use the seeds for propagation, you do not need to worry.

Harvest time

They are harvested in late summer, when the seeds are fully mature. You can recognise ripe fruit by the fact that the pods are dried and dark.

How to harvest lupin seeds?

The seeds can be easily squeezed out of the mature pods. Mature seeds have a beautiful dark colour. The seeds are cleaned with water and then dried for storage. In a screw-top jar in a cool, dark place, the seeds are still germinable after two to three years.

The harvested lupin seeds can be processed in many ways.