Name: lupin, lupine, Lupinus polyphyllus, L. perennis, L. arboreous.
Height: usually 0.6 to 2m.
Foliage: green dissected compound leaves, arranged radially rising from herbaceous stems.
Climate: prefers dry summers and cool, wet winters.
Soil: prefers well-drained, moderately fertile sandy soil.
Position: full sun to partial shade in warmer temperate climates.
Flowering and fruiting: colourful vertical spikes of single-coloured or two-toned pea-like flowers from spring to early summer, developing into flat, hairy, pea-like pods that split open when mature, shedding the hard seeds.
Feeding: use a controlled release organic fertiliser specifically for flowering plants in early spring. Avoid fertilisers high in nitrogen as lupins have nitrogen-fixing roots.
Watering: regular watering throughout the spring and summer growth periods.
Lupins form mounding upright clumps of fresh green foliage, dissected into leaflets like the spokes of a wheel. Upright spikes of dramatic flowers in singular or two-tone colour combinations arise from the domes of foliage in spring and early summer. These colours include shades of blue, purple, pink, yellow, red, orange and white. There are dwarf cultivars from 0.6 metres high to tall varieties up to 3 metres. The most famous are the Russell lupins, although many species and cultivars are grown as green manure crops, to provide fodder for animals, or for human food production including flour.
Lupins will grow in most temperate climates with dry summers and cool, moist winters. They prefer to be planted in full sun or partially shaded environments in hot climates. Lupins usually die back to the ground in autumn before reshooting the following spring. They can be used in cottage gardens and borders to provide pops of early summer colour or mass planted for a dramatic impact.
Lupins grow best in free draining soils with a pH around 6.5–7. They can survive in relatively poor soils due to their nitrogen-fixing roots. Adequate moisture in their growth phase from spring to early summer is essential for healthy growth. Winter wet conditions may cause root rot.
On farms, lupins are often planted by seed, grown to maturity and then turned into the soil, before planting with other vegetable or grain crops, as their nitrogen-fixing roots improve nutrient-deficient soils. This is often called a ‘green manure’ crop.
Use organic or controlled release fertilisers low in nitrogen in early spring. Avoid fertilisers high in nitrogen as lupins have nitrogen-fixing roots that make their own, even in poor soils.
Slugs and snails can cause problems for small lupin plants in spring and these are best controlled organically with beer traps, handpicking by torchlight, and barriers of copper tape or by using iron chelate based snail pellets. These are the safest to use in the home garden for your pets and the local wildlife.
Anthracnose is a serious disease, particularly during humid conditions, which can cause dieback of young shoots, brown scarring of stems, browning and dead patches on the leaves, and rotting of the crown. Most infected plants usually die, and infected plants should be burnt to destroy the fungus. It is usually spread through the seed, so many seed companies now heat-treat their seeds to prevent infection.
The seed of annual or perennial species should be sown during spring, summer or autumn in individual jiffy pots, seed modules or small pots.
For perennial varieties including the Russell hybrids, you can propagate by carefully dividing the crown in early spring before growth commences, to avoid the possibility of root rot.
Alternatively, take a cutting from the base of the stem of new shoots in mid to late spring with a small slice of the yellow rootstock attached. Place in pure perlite to prevent rotting.
Foxgloves (digitalis): statuesque biennials and perennials with spikes of delicate two lipped tubular flowers in spring.
Poppies (papaver): annuals, biennials and perennials with cupped petals and vibrant red, white, purple or pink blooms in spring.
Dahlias: vibrant autumn flowering perennials for mixed herbaceous borders or growing pots, with hot coloured flowers and interesting foliage.
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