How to grow lupines
Lupins (Lupinus) are a genus of the Fabaceae family. In total, the genus comprises about 200 different species. Lupine originated in North America. It was introduced in Europe at the beginning of the 19th century and has since been growing in Germany as a wild perennial. There are both perennial and annual species. In the garden, breeding forms of the perennial multileaved lupin (Lupinus polyphyllus) are predominantly found. Lupine convinces with fast growth and a conspicuous flowering that lasts from early summer to August. The variety of the numerous varieties not only brings colourfulness to the farmer’s garden. Some varieties are also an effective green fertilizer. In beds, the perennial perennial shrub serves as a reliable filler, since it also sows itself.
Appearance and growth
Lupins can grow up to three meters high depending on the species. The most commonly used garden lupine grows to 80 to 120 centimetres in height, of which the wonderful dense flowering candles take up to 50 centimetres. The butterfly flowers are arranged in terminal racemes or ears and shine in white, violet, pink, red or yellow, depending on the variety, there are often two-coloured variants. The flowers open from the end of May to the beginning of August, always starting with the lowest of each candle. For this reason, lupine flowers in principle throughout the summer. The leaves of the lupine are also very decorative. Each hand-shaped pinnate leaf consists of nine to seventeen lanceolate leaves.
Location and soil
Lupins unfold their full effect in growth form and colour intensity in open, sunny locations. In more shady places, the willingness to flower diminishes and they lose stability. Lupins grow in any soil that is not too rich in nutrients and low in lime. However, if the soil is too calcareous, the leaves turn yellow. Lupins do not tolerate waterlogging. A well ventilated, medium to light soil is ideal.
Sowing and planting lupines
One-year-old lupins are sown directly into the bed in May. The perennial representatives should be planted in spring, as they often do not grow properly in autumn. If you want to cultivate lupines in a tub, you should choose a very small variety and a tall pot, as tall varieties can easily bend in the wind.
If necessary, you should support the flower stems of the higher growing lupin varieties. Immediate pruning after flowering usually stimulates post-flowering in summer. The total pruning of the plant often leads to complete failure. Slight loosening of the soil around the plant, especially after rain, rewards the lupine with better flowering. Lupins should not be fertilized too much, otherwise the plants become more susceptible to diseases and pests. However, fertilization with bone meal can improve the stability of the stems. However, fertilizers with a high nitrogen content are completely unsuitable because the additional nitrogen causes the roots to rot.
It is advisable to give Lupinen a “rejuvenating cure” about every three years: Divide up dug out rootstocks in spring and put the new shoots back into the garden.
Usage of lupines
The so-called Russel hybrids (Lupinus polyphyllus) are particularly suitable for the perennial garden. Lupins stand advantageously in small groups of three to ten plants in front of a hedge or group of trees. In addition to late flowering perennials such as Myrtle Aster (Aster ericoides), Summer Phlox (Phlox paniculata) or Sun Hat (Echinacea), the perennial shrub is particularly attractive. In the cottage garden, the perennial multileaf lupins radiate their rural charm between daisies, poppies, irises and night villas. The West Country Lupines are a true colour miracle. The robust series from England shines with extreme luminosity. Varieties such as ‘Masterpiece’ stand out due to their large inflorescences. Lupine does not lose any of its effect in the vase either, and many varieties spread a pleasant scent.
Since lupins have a high protein content, the seeds were already processed and eaten by our ancestors. In farmer’s gardens, blue lupine used to be grown as a substitute for coffee. Food and medicine have been obtained from lupine seeds since ancient times. But be careful with experiments: The lupins growing in the garden are poisonous in all parts, since lupins contain large quantities of alkaloids. In the feed and food industry specially bred low alkaloid varieties are used and processed into spreads, ice cream, milk, flour, coffee or even sausage and meat substitutes.
Lupines as green fertilizer
Certain lupin varieties are excellent for green manuring, especially if you want to loosen the soil deeply, enrich it with nitrogen or incorporate organic fertiliser into the soil. Lupins are industrious nitrogen collectors. At its roots there are so-called nodule bacteria (rhizobia), which store the nitrogen that the plant has absorbed from the soil air in the nodule. This can be used for soil improvement in the garden. Especially when beds are newly planted, it is advisable to first sow narrow-leaved lupine (Lupinus angustifolius), yellow lupine (L. luteus) or white lupine (L. albus). All three species, also known as sweet lupins, not only enrich the soil with nitrogen, but are also deep-rooted – their tap roots penetrate up to two metres into the soil and can thus loosen up compacted layers.
Lupins are sown as green manure from April to August. When sowing, add algae lime or stone flour to the soil – this promotes the nodule bacteria. Since lupins are hardy, they can only be sown after the vegetable bed has been harvested. Mow the annual plants after winter at the latest and leave them as a mulch layer. Finally, work the dried plant remains flat into the soil. Thus the nitrogen reaches the soil and is available to the following plants. The rotting organic material of the lupines also produces valuable humus. Around four weeks later, the beds can be ordered as desired.
Important species and varieties
Today, numerous species and especially varieties of lupin are available on the market. The great diversity of varieties was created at the beginning of the 20th century by crossbreeding perennial multileaved lupins from America with other annual and perennial species. The variants of the English breeder George Russell (1857-1951) are widespread until today. The so-called lock series includes the varieties ‘Fräulein’ (white), ‘Kronleuchter’ (yellow) and ‘Edelknabe’ (carmine red). These grow to a height of 80 to 100 centimetres and flower for many weeks in strong but also delicate colours.
Much lower are the different coloured varieties of the dwarf garden lupins (Lupinus-Nanus-Russell hybrids). They grow to a height of 50 to 60 centimetres and are therefore also suitable for pot planting. In addition to these tried and tested perennials, newer variants are increasingly gaining ground. These also come from an English nursery and are summarized under the name Westcountry series. Many of the tall, yet stable lupins are bicoloured or multicoloured and thus the absolute stars in the perennial bed. Extravagant varieties such as ‘Masterpiece’ and ‘Salmon Star’ are preferably surrounded by discreet companions such as cranesbill or lady’s mantle so that they don’t steal the show from the lupines.
In general, lupins are propagated by sowing from April to July. The seeds germinate better if they are roughened and left to soak in water for 24 hours. When lupins are propagated over cuttings, the offspring wear the same colour. To propagate the cuttings in spring, cut off young shoots five to ten centimetres long from the plant base and remove all but the top one or two leaves. To prevent the soft shoots from rotting, they are inserted into loose substrate, for example expanded clay in pots. Sink the cuttings halfway and place them warm, but not fully sunny, in even humidity. After four to six weeks, the rooted cuttings can be planted individually in potting soil. Then you only have to water the lupin offspring from time to time and plant it out into the bed about six weeks later.
Diseases and pests
Lupine is occasionally attacked by lupine aphids. This pest, introduced to us via Great Britain in the 1980s, mostly occurs in large colonies and simply causes lupins to tip over. If only a few specimens appear, the problem can be solved by collecting them, with larger colonies only the use of insecticides usually helps. If you discover that the young shoots of your lupin die off, necrotic spots appear on the leaf edges or cracks form on the stems and older leaves, your plant probably suffers from anthracnosis. Unfortunately, the only thing that helps here is to remove the infested lupine. Furthermore, there may be an infestation with powdery mildew. Fresh shoots of lupine are also popular with snails.