What Does It Look Like?
What is it?
Calomba Daisy (Oncosiphon suffruticosum) is an upright, dense multi-stemmed, spreading, aromatic, annual herb, growing to 200–600 mm tall, sometimes to 1 metre high. The first leaves form a small rosette, from which grows an upright, leafy flowering stem. The erect stems are stout, becoming woody with age, and usually un-branched below the flower head. Leaves are 20–40 mm long, and 10–20 mm wide, in outline oblanceolate (lance shaped, about 4 times as long as broad, broadest in the upper half, tapering to a narrow base), and deeply divided 2-3 times into thin lobes with the ultimate lobes (all final lobes) under 1 mm wide, grey-green, and covered with short soft hairs, without a leaf-stalk, with the base clasping the stem.
The flower-heads are yellow, in ball-shaped heads at the top of the stems, grouped into dense flat-topped terminal clusters called corymbs (many flowered inflorescence with branches starting at different points but reaching about the same height). There are numerous to a hundred flower-heads per stem, and many to a hundred or more stems per plant. Each flower head is borne on varying sized flower stalks to 10 mm long. Flower-heads are 3–5 mm diameter, with numerous tightly packed 4-lobed yellow flower (disc florets) just exceeding the surrounding involucral bracts (leaf like structures surrounding the flower-heads). These bracts are 2-seriate, oblong (length a few times greater than width, with sides almost parallel and ends rounded), 1–3 mm long, bracts sub-equal, mostly (dry and membranous), without hairs. The receptacle, the portion at the top of the stem where the flowers of the head are borne, is conical and about 1 mm diameter at maturity.
The fruits or 'seeds' (cypselas) are wedge-shaped; with straight sides converging at base, about 1–1.5 mm long, grey-brown, more-or-less 3-angled and ribbed and minutely crowned with white scales to 0.5–1 mm long (Animal and Plant Control Commission of SA 2000; Parsons & Cuthbertson 2001; Thompson 2007; VicFlora 2016).
For further information and assistance with identification of Calomba Daisy, contact the herbarium in your state or territory.
Growth form (weed type/habit)
Where it currently grows? Preferred habitat
Calomba Daisy occurs mainly in loose sandy soils in disturbed areas such as cultivated fields, degraded pastures, roadsides and waste areas (Parsons & Cuthbertson 2001). It is most common on red or red/brown (gravelly) clay loams, or granite and limestone soils. Calomba daisy can also be found in seasonally inundated areas and clay pans. The areas where it may establish further are sandy mallee soils and pastoral areas (Government of South Australia 2014).
In Western Australia, it also occurs on red clay loam, red-brown gravelly clay loam, granite, limestone. Seasonally inundated areas, clay pans, paddocks, road verges. (Western Australian Herbarium 1998–).
Are there similar species?
Calomba Daisy can be distinguished from:
Globe Chamomile (Oncosiphon piluliferum) by its greater height (60 cm compared to 40 cm), longer leaves (4 cm compared to 2 cm), smaller flower heads when in full bloom (3-5 mm diameter compared to 5-8 mm), a different shaped flower head (globose but flattened on top compared to wholly globose) and a greater number of flower heads per stem (numerous to hundreds, compared to several to numerous) (Thompson 2007). Globe Chamomile, also of South African origin, occurs in south-western Western Australia (Thompson 2007). Globe chamomile (Oncosiphon piluliferum) has rounder, globe shaped flower heads whereas calomba daisy (Oncosiphon suffruticosum) has more 'club' shaped flower heads.
The genus can be distinguished from Pentzia by its habit as it is herbaceous rather than woody.
It may be distinguished from Matricaria by the different shaped flower head which is subglobose (not quite spherical) rather than ovoid (egg-shaped), and the presence of hairs on the plant (Matricaria is hairless) (Thompson 2007).