Weed of the Week - Siratro (Macroptilium atropurpureum)
SIRATRO (Macroptilium atropurpureum) is a vine legume that is native to the tropical and subtropical regions of North, Central and South America.
Siratro is regarded as an environmental weed in Queensland, the Northern Territory, northern Western Australia and northern New South Wales.
Siratro was originally introduced into northern Australia as a fodder plant but is incredibly invasive and damaging in bushland and along river edges.
Siratro is a weed of disturbed sites, waste areas, roadsides, fences, gardens, coastal environments, urban bushland, watercourses (ie. riparian areas), horticultural crops, and plantation crops (eg. sugar cane).
As an environmental weed, Siratro can form dense infestations along forest edges, and grows over native shrubs, ground covers, and young trees by smothering them under its dense vines and not allowing them enough sunlight or soil nutrients to grow.
It is also common in vegetation around waterways and in coastal sand dune vegetation. Siratro is also a problem in revegetation sites, where it smothers young trees and shrubs before they become established. It spreads by cuttings and seeds.
Siratro is a creeping or climbing legume, with bright green leaves between 2-7 cm long, with each leaf having three broad leaflets. The two lower leaflets will often have an extra rounded lobe, and the leaves have silky hairs on their underside.
"Sweet pea-like" dark red-purple flowers are borne on long spikes most of the year. After flowering, narrow pods 5-10 cm long appear.
This species reproduces by seed. Seeds are forcibly ejected from the pod when mature, and can be thrown for several metres.
They can also be dispersed greater distances through water movement and following ingestion by cattle.
The stems are ribbed lengthwise and hairy (i.e. pubescent).
Older stems at the base of older plants are fibrous and about 5 mm thick, while younger stems are slender (1-2 mm thick) and green in colour.
Flowering occurs throughout the year.
The long and narrow (ie. linear) pods are cylindrical and turn from green to brown in colour as they mature.
These pods (5-10cm long and 3-5mm wide) are shortly hairy (ie. pubescent) and split open when mature to release about 12 seeds.
The seeds (about 4mm long and 2mm wide) are somewhat egg-shaped (ie. ovoid) or slightly kidney-shaped and speckled light brown and black.
Siratro can be difficult to be hand pulled due to the long tap root and will often break off in several places along the stems as the vine is often wrapped along the supporting shrub. Tangled growth may need to be cleared using a brush cutter. As it is a legume, livestock eats the vine for nitrogen nutriment.
Soil cultivation is often the only way to remove vine but also serves to increase germination of seeds so follow cultivation is required.
Herbicides are very effective in controlling Siratro (Macroptilium atropurpureum) but since it grows over other plants there is strong chance of killing the host plant.
Article writer Ian Read can be contacted on 4159 9365, or email ian.read7@big pond.com.au for free weed identification and native plants advice, and for landscaping and weed control.
Phone Landcare president Michael Johnson on 0422 297 062 for weed project details and monthly meeting times, or email firstname.lastname@example.org
The Bundaberg Landcare Nursery at the Salvation Army Tom Quinn Centre, Doctor May's Rd, is open on Wednesdays, Thursdays and Fridays, 10am-4pm for native plants.