Cytisus Is from the Greek kytisos and was the name of a fodder plant that was probably Medicago arborea. Palmensis Tagasaste is its common name in the Canary Islands (its country of origin).
Tree Lucerne refers to its size and its similarity to Lucerne (Medicago sativa).
Tree Lucerne or Tagasaste (Chamaecytisus palmensis) is a perennial, large shrub or small tree up to 5 m high with weeping branches and greyish green, trifoliate, softly hairy foliage. The leaves are divided into 3 oval leaflets each 10-45 mm long. The scented, white to cream pea flowers are each 12-17 mm long and occur in small showy clusters. The seed pod is flat, 40-50 mm long and 8-12 mm wide. Tagasaste is native to the Canary Islands. It is grown as a fodder plant and it has since become weedy along roadsides, sometimes invading bushland. It is common between Albany and Esperance and flowers in winter and early spring. Seed may remain viable in the soil for more than 10 years but seedlings rarely establish in dense shade.
Three leaflets (trifoliate). Alternate. Stipules - Small or absent. Petiole - Short petiole on the leaf and shorter petioles on each of the leaflets. Hairy. Blade - Of leaflet, greyish green, narrowly oval, 10-45 mm long by 4-13 mm wide. Acute or obtuse tip with a tiny point. Rounded sides. Tapered base. Hairless on top, tiny hairs to almost hairless underneath. Often dark green on top and lighter green to whitish underneath due to the downy hairs.
Erect, olive green to grey brown, bushy, up to 5 m tall, with many drooping branches covered with soft grey hairs when young.
Flowers in umbels of 3-7 flowers usually at the ends of short branches. Flower stalks(pedicels) 7-20 mm long with downy hairs and a parallel sided bract.
White to cream, pea type and aromatic. Ovary - Stalkless. Style incurved, hairless. Stigma at the end and flat topped. Sepals -9-12 mm long, tubular and lipped, downy hairy, with 2 small bracts underneath. Tube about 5 mm long. Upper lip broad with 2 lobes that are joined for most of their length. Lower lip with 3 short lobes. Petals - White to cream. Standard petal 14-17 mm long. Limb broadly egg shaped. Wings 13-16 mm long. Keel, 13-16 mm, curved and slightly beaked. Stamens - Filaments in a closed sheath. Anthers - Alternately long and short. Long ones, oblong and attached at the base. Short ones, egg shaped and attached on the back.
Stalkless, green brown, flattened, oblong, slightly curved, 2 valved pod, 40-50 mm long by 8-12 mm wide, hairy. Not constricted between the seeds. Contains around 10 seeds, which are released explosively when ripe.
10 mm long, oval with an appendage (aril). 45 seeds per gram.
Deep, woody, branching tap root that is thickened at the crown. Many shallow laterals.
Perennial, fast growing shrub or tree. Seeds or seedlings are normally planted in autumn. It reaches sexual maturity in 3 years.
Sensitive to waterlogging. Young plants frost sensitive, older plants frost tolerant. Fixes nitrogen. Tolerates drought, wind and poor fertility soils. It prefers full sun but will grow in partly shaded areas.
July to October in SA. June to September in Perth. Winter and early spring in WA. June to October in SE Australia.
Seed Biology and Germination:
Has high levels of hard seed that may remain dormant for more than 10 years. Produces large quantities of seed but the germinability is often less than 50%. Seed requires scarification or hot water treatment to achieve reasonable levels of germination.
Population Dynamics and Dispersal:
Spread initially by intentional planting then by seed dispersed by animals, birds, ants?, soil movement and natural means. Ripe seed can be dispersed several metres by the explosive opening of pods. Dumping of garden refuse is a common source of infestation. Germination is encouraged by fire and disturbance which often leads to a mass germination and increase in infestation density.
Origin and History:
Canary Islands. Introduced as a fodder shrub.
ACT, NSW, SA, TAS, VIC, WA. New Zealand, USA.
Courtesy Australia's Virtual Herbarium.
Temperate. Mediterranean. It is more invasive in the high rainfall areas with more than 500 mm rainfall.
Grows on a wide range of soils. Appears to be more invasive on gravel soils.
Ornamental hedge and garden plant. Cultivated as a fodder shrub. Young shoots and leaves are nutritious and palatable. Planted as a wind break and to protect soil from wind erosion. Honey plant.
Weed of roadsides, bushland and disturbed areas. Increases soil nitrogen levels which may affect the persistence of some native species or encourage invasion by grasses. It can form fairly dense stands exuding most other species and reducing regeneration of overstorey species especially on gravel soils in the high rainfall areas.
Contains alkaloids. No cases have been recorded in Australia. Toxicity would only be suspected where large quantities were eaten.
Nausea, convulsions, respiratory failure and death.
Management and Control:
Grazing needs to be controlled to prevent plants being ringbarked or it can be used to control plants that have escaped. Don't disturb areas unless follow up control is planned.
It will take several years to achieve control. Chain or bull dose trees, burn, then spray regrowth and seedlings. Heavy grazing can be used to provide control by ring barking the trees and consuming the seedlings. A mixture of 1 L of Access® in 60 L of diesel applied to the lower 50 cm of trunks can be used for individual trees. Seedlings (and trees) can be sprayed with a mixture of 0.5 g metsulfuron(600g/kg) plus 25 mL Pulse® in 10 L water in spring or autumn. Repeat annually until no more seedling appear. This may take several years. 2 L/ha Tordon®75-D or 10 kg/ha Tordon® granules provide control of existing plants and residual control of seedlings but may affect other trees and scrub. Metsulfuron and Tordon® will kill many native species it contacts at these rates. 800 g/ha Lontrel®750 is preferred for use near Eucalypts. Replant to native species at least 12 months after the last spray to reduce light levels because very few Tagasaste seedling will establish in dense shade. Hand weed any Tagasaste seedlings as they appear. Seedlings can be hand pulled but larger plants tend to break off and regrow from the base. Glyphosate is relatively ineffective.
Broom (Cytisus scoparius) White Broom (Cytisus multiflorus)
Plants of similar appearance:
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Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #407.2.
Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P246.
Moore, J.H. and Wheeler, J.R. (2008). Southern Weeds and their Control. (Second Edition). Department of Agriculture and Food Western Australia. P176-177. Photos.
Muyt, A. (2001). Bush Invaders of South-East Australia: a guide to the identification and control of environmental weeds found in South East Australia. (R.G and F.J. Richardson, Australia). P163-164. Photos.
Reid, R.L. (1990) The Manual of Australian Agriculture. (Butterworths, Sydney). P258.