A look at Lupins

Lupins must be one of the most recognisable of all garden plants. Even non-gardeners know a lupin. Old jigsaws and chocolate boxes with scenes of thatched cottages always feature lupins, roses and hollyhocks in the garden. The name Lupinus is interesting; it is the Latin for wolflike. Collins Dictionary says the name originates from the belief that lupins exhausted the soil in a wolfish manner, an erroneous belief as we now know that lupins thrive in already poor soil.

Lupins are legumes, members of the pea family. There are several hundred species, most of which are native to North and South America, though a few originate in North Africa and Mediterranean regions. They are mostly herbaceous plants, both perennial and annual, but there are shrubby forms known as tree lupins. Despite the name these are usually small shrubs up to 1.5m high though there is one species (L jaimehintoniana) growing in Mexico which can reach 8m high. Some gardeners grow annual species as a green manure, but the vast majority of lupins seen in gardens are modern perennial hybrids derived from the North American species L polyphyllus.

Apart from their continued popularity in gardens, lupins are likely to make the news in coming years for two other reasons. Firstly, they have become invasive species in South Island of New Zealand, and in Finland and Norway, and are disrupting the ecology of native flora. Secondly, lupins are generating much interest as a potential large-scale human food crop. Historically we know that lupin seeds were eaten in the Andes as long as 6000 years ago, and around the Mediterranean 3000 years ago. The Romans planted lupins as they colonised Europe and they are a popular snack in the Middle East today. They do, however, require specific treatments to remove bitterness and make them palatable, and only certain species are suitable. There is also a risk of allergic reaction in people who have a peanut allergy. So, please do not eat the lupins in your garden, stick to commercially produced products. Lupin seeds, also called beans, are used as an alternative to soya beans and fed to pigs, poultry, and ruminants. They are gluten free, rich in fibre and antioxidants, and contain less fat than soya beans. Their ability to fix nitrogen and colonise and improve poor soils, makes them an important potential food crop for humans. Currently 85% of the world’s lupin seeds are produced in Western Australia.

Modern hybrid lupins do best in moist (but not soggy) soil in full sun, but they will grow in partial shade. Being members of the pea family, they can tolerate dry periods once established, and they do not require regular feeding or a soil rich in nutrients. They look particularly good planted in a drifts, or elongated groups, where their strong vertical form makes an excellent contrast amongst other plants, especially grasses. For most of us with less room, they are best positioned towards the back of the border. A relatively sheltered site is preferred as the heavy flower spikes catch the wind, but they generally do not need staking. Guinness World Records reports that a lupin grown by A H Fennell (of Palatine, near Dublin) reached a height of 1.96 m (6 ft 5¼in). Blooms on that scale would need staking.

Deadheading and slug control are the keys to growing lupins well. Slugs and snails are particularly fond of them and can ravage the emerging shoots in spring as soon as they start to grow so appropriate protection is needed. Lupins that have “died” over the winter may have been munched to oblivion as they commenced growth. One solution might be to grow your lupins in pots, but they prefer to be in the ground and do not perform well in containers.

Normally, flowers are dead headed as the last bloom goes over, but the lupin spike opens from the bottom upwards, and there will be developing seed pods at the bottom before the top buds have opened. Here in the bumblebee garden, we deadhead the lupins once half the spike has faded. It is hard to cut off so many unopened buds, but at this point the spike begins to look scruffy. We have found this method reduces the gap before the next flowers appear and prolongs continuity of the display.