T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Lupinus arboreus (Tree Lupin)

Kingdom:   Plantae
(Unranked):        Angiosperms
(Unranked):        Eudicots
(Unranked):        Rosids
Order:       Fabales
Family:      Fabaceae
Subfamily: Faboideae
Tribe:        Genisteae
Genus:      Lupinus
Subgenus: Platycarpos
Species:     L. arboreus
Binomial name: Lupinus arboreus
Common name: Tree lupin, Yellow bush lupin

Lupinus arboreus is a species of flowering plant in the legume family and is native to California were it is widely distributed among coastal scrub and sand dunes. It is an evergreen short-lived (up to 7 years) perennial plant that usually grows 1–1.5 m tall but can grow up to 2 m in sheltered situations. L. arboreus is less common now as often attacked by fungal disease.
It has green to gray-green palmate leaves, with 5-12 leaflets per leaf. The leaflets are 2–6 cm long, often sparsely covered with fine silky hairs. The leaves are bitter and not usually eaten by stock.
During Oct-May it bears many racemes (30 cm long) of sweetly scented, soft pale yellow, pea-like flowers (15-18 mm long) which are usually pale yellow (rarely white or bluish).
The seed pods are stout, softly hairy (40-80 mm long) and when ripe they split explosively to disperse dark brown, mottled seeds (4-6 mm long).
It has a very deep taproot and has been used for holding together sandy land.

In New Zealand it is an invasive species habiting short tussock land, bare land, riverbeds, coastal sandy, regenerating forest, forest margins and well drained areas.  Like many members of the Fabaceae, it is an effective fixer of nitrogen in the soil. Where it has been introduced, it changes the chemistry of the soil, and therefore allows other exotics to establish themselves, to the detriment of native vegetation adapted to low nitrogen levels.











Underside of the leaves.