Tree Lupin, Yellow bush lupine
Lupinus arboreus
Family: Fabaceae or Leguminosae
What it is like
Lupinus arboreus is an evergreen Shrub growing to 1.5 m (5ft) by 1.2 m (4ft in) at a fast rate. See above for USDA hardiness. It is hardy to UK zone 8. It is in leaf all year, in flower from May to August. The species is hermaphrodite (has both male and female organs) and is pollinated by Bees. It can fix Nitrogen. Suitable for: light (sandy) and medium (loamy) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It cannot grow in the shade. It prefers dry or moist soil and can tolerate drought. The plant can tolerate maritime exposure.
Height (m): 1.5
Where it is found
Stable sand dunes, coastal scrub and pine forest close to the coast. Naturalized by the sea in S. England.
South-western N. America - California to Oregon. Naturalized in S. England.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 0
Medicine
Rating: 0
Other
Rating: 5
A bright yellow dye is obtained from the flowers. The root fibres have been used to make a string for making nets etc. Plants are used in land reclamation schemes to stabilize sandy soils and dunes. Because they are fast growing and tolerant of maritime exposure, they quickly provide shelter for other plants as well as enriching the soil with nitrogen. An excellent pioneering plant in permaculture, even in exposed areas it grows rapidly to its maximum height of about 1.5 metres and will give shelter to enable other less tolerant plants to become established. It is especially useful for helping the establishment of shrubs and herbaceous perennials in small gardens.
Dye: Plants that provide dyes.
Pioneer: Plants, usually trees and shrubs, that can be used to reforest land.
Soil reclamation: Plants that can be grown in such circumstances an the spoil tips of mines in order to restore fertility.
String: Plants that can be used for string or can be easily made into a string. See also Fibre. Plants for ropes may be included.
Dynamic accumulator: Plants that gather minerals or nutrients from the soil and store them in a more bioavailable form and in high concentration in their tissues. Used as fertilizer or to improve mulch.
Food Forest: Plants for Edible Forest Gardens and Food Forests.
Nitrogen Fixer: Plants that fix nitrogen in the soil
Scented Plants: Plants noted for their scent
How it is grown
Requires a well-drained dry or moist soil in a sunny position. Prefers an alkaline soil. Grows well near the coast, resisting maritime exposure. Established plants are drought tolerant. Plants can be grown in quite coarse grass, which can be cut annually in the autumn. Hardy to about -15°c. Plants are hardy in all but severe winters in Britain, though they become less hardy with age. A fast-growing but short-lived plant, especially when growing in rich soils. Plants have reached 2.7 metres tall and wide within 4 years from seed in a rich soil, flowering and producing seed prolifically. Plants self-sow when in a suitable position. The flowers bear the fragrance of white clover. This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby.
Propagating it: Pre-soak the seed for 24 hours in warm water and then sow in early spring in a greenhouse. Germination should take place within a couple of weeks. When they are large enough to handle, prick the seedlings out into individual pots and plant them out in early summer. It should also be possible to sow the seed in situ in mid to late spring. Protect the seed from mice. Cuttings of short side-shoots with a heel, July/August in a frame.
Best place to grow: Woodland Garden Sunny Edge; Cultivated Beds;
Habit: Shrub
Hardiness: 7-10
Growth: Fast
Soil: Light (sandy), medium
Shade: No shade
Moisture: Dry, moist
Things to keep in mind
The seed of many lupin species contain bitter-tasting toxic alkaloids, though there are often sweet varieties within that species that are completely wholesome. Taste is a very clear indicator. These toxic alkaloids can be leeched out of the seed by soaking it overnight and discarding the soak water. It may also be necessary to change the water once during cooking. Fungal toxins also readily invade the crushed seed and can cause chronic illness.