What Does It Look Like?
What is it?
Paddy's Lucerne (Sida rhombifolia) is an upright, perennial sub-shrub which may be up to 1.5 m tall and when young has quite a dense covering of minute hairs. These are mostly lost as the plants mature. The leaves are egg-shaped, oval-shaped or rhombic in outline and 15–90 mm long. The upper two-thirds of the leaf blades are shallowly toothed.
The yellow flowers are about 15 mm across and are borne singly along the stems (that is, there is one per leaf axil) and become more crowded towards the tip of the stems. The flower-stalks are up to 35 mm long when the flower first opens but grow longer as the fruit matures.
The outer whorl of the flowers (the calyx) encloses the mature fruit. The fruit (called a schizocarp) is 4.5–5.5 mm in diameter. It splits into 9–11 segments called mericarps. Each mericarp is about 2.5 mm high and usually splits in half at the apex, with each apex being awned. The awns are about 0.8 mm long, hairless or sparsely hairy. Very occasionally single-awned mericarps are present instead of the usual 2-awned mericarps (Barker, unpublished manuscript).
For further information and assistance with identification of Paddy's Lucerne contact the herbarium in your state or territory.
Flower colour
Yellow
Growth form (weed type/habit)
Shrub
Where it currently grows? Preferred habitat
Paddy's Lucerne is a weed of cultivated and otherwise disturbed sites such as roadside verges and degraded pastures in tropical to warm-temperate climates. It tolerates a range of soil types (Parsons & Cuthbertson 2001; Navie 2004).
Are there similar species?
Paddy's Lucerne is most likely to be confused with other species of Sida, especially Flannel Weed (S. cordifolia) and Spinyhead Sida (S. acuta). It may also be confused with S. spinosa, S. subspicata, Malvastrum americanum and M. coromandelianum (Navie 2004).
Paddy's Lucerne has oval (elliptic), lance-shaped (lanceolate) or diamond-shaped (rhomboid) leaves with a dense covering of hairs on their undersides and a sparse covering of hairs on their upper surfaces. These leaves usually have rounded tips (obtuse apices). Its flowers are borne singly on long and thin stalks (10–40 mm long) and their bracts (calyces) are sparsely hairy. The fruit usually break up into 8–12 mericarps that are topped with two short awns (0.5–1 mm long) (Navie 2004).
Flannel Weed has broad or heart-shaped (cordate) leaves that are densely covered in small whitish coloured hairs (on both surfaces) that give them a felty texture. Its flowers are borne in small, dense, clusters on short stalks (2–4 mm long) and their bracts (calyces) are densely hairy (unlike the sparsely hairy bracts of Paddy's Lucernne). The mericarps have longer, slender awns (2.5–3.5 mm long) (Navie 2004).
Spinyhead Sida has elongated (lanceolate) leaves that are hairless or sparsely hairy on both surfaces and have pointed tips (acute apices), not rounded as in Paddy's Lucerne. Its flowers are borne singly or in small clusters on short stalks (2–8 mm long). The fruit break up into 5–8 wedge-shaped mericarps (Navie 2004).
Spiny Sida has flowers are borne singly or in small clusters on relatively short stalks (3–15 mm long). The fruit usually break up into only 5 mericarps (Navie 2004).
Spiked Sida (Sida subspicata) has relatively narrow (lanceolate) to broad (ovate or oblong) leaves with a dense covering of hairs on both surfaces (but more so underneath). Its flowers are almost stalkless and borne in elongated clusters (spikes) with a few small leaves sometimes interspersed between them. Their bracts (calyces) are finely hairy and the fruit break up into 4–6 mericarps that have rounded tips (Navie 2004).
Malvastrum species can be distinguished from Sida species because the flowers have what is known as an epicalyx, in this case 3 free segments situated immediately below the calyx, which species of Sida lack (Barker, unpubl. manuscript)
