110 Plant Protection Quarterly VoI.12(3) 1997 Description Detailed descriptions of Oxalis pes-caprae have been given by Clarke (1934), Salter (1944), Meadly (1955), Michael (1958), Par­ Review sons (1973), Peirce (1981, 1983), Lander (1987) and Parsons and Cuthbertson (1992). The fo llowing description is adapted from Clarke (1934): ' ... an almost glabrous The Biology of Australian Weeds perennial, with an annual vertical subter­ ranean stem 2-8 mm thick at ground level 31. Oxalis pes-caprae L. but tapering below into a fine thread-like extension which connects to the parent J.R. Peirce, Agriculture Western Australia, Baron-Hay Court, South Perth, bulb. The whitish, mostly unbranched stem has numerous hair-like adventitious Western Australia 6151, Australia. roots and one to several bulbs in the axils of scale leaves. Often below the bulb is a Name fusiform translucent structure formed by Oxalis, derived from the Greek oxys mean­ now know as members of the family the tuberization of one of the secondary ing sour or sharp tasting, is a Greco-Latin Oxalidaceae. Although it was first de­ roots. word used for certain plants with acidic scribed as O. pes-caprae L., Thunberg At ground level the stem produces sap. Linnaeus (1753) narrowed its use as a (1781), cited by Symon (1961) and Michael leaves which consist of a short, flattened generic name to include only plants we (1964), named the species O. cernua leaf base, a long, cylindrical petiole up to Thunb.; cerullo referring to the night time 13 cm long, and three terminal digitate drooping, or nodding movements associ­ leaflets. Leaflets are obcordate, two-lobed, ated with the foliage and flowers (Clarke 1-4 cm broad, often marked with small 1934). Because centua was so widely ac­ purple spots. Flowers are yellow, droop­ cepted, this name was preferred until ing,3-16 in umbels on long radical pedun­ Sa lter (1939) had the original name re­ cles. Sepals 6 rnm long have two orange establi shed. The name pes-cap rae comes calli at their tips; petals 25 mm long; inner from the Latin pes meaning foot and caprae stamens longer, each with a staminodial of a goat, suggesting that the shape of the appendage towards the base. Capsule ob­ leaf is like a goat's foot (Parsons and long-acuminate, rarely maturing in Aus­ Cuthbertson 1992). Oxalidaceae is a small tralia. Flowering takes place during June­ family of eight genera containing some October'. The plant is illustrated in Fig­ 900 species of mostly herbs with fleshy ure 1. rootstocks and an acid taste (Parsons and Salter (1944) described O. pes-caprae in Cuthbertson 1992). South Africa as a variable species. Michael There are many common names fo r (1964), after studying many of the infesta­ O. pes-caprae L. Soursob or soursobs are tions through the southern states of Aus­ the main common names in Australia tralia, also concluded that considerable (Clarke 1934), while in South Nrica it is variation existed within Australia. He iden­ referred to as geelsuring, oxali s, sorrel and tified major differences in markings on the yellow sorrel (Parsons and Cuthbertson sepals, size and colouring of the petals as 1992). These authors also list buttercup well as differences in shape and markings oxalis as a common name in the UK and on the leaflets. More recently, Peirce USA and cape cowslip for the UK. (1973) expanded the number of variations Sourgrass, Bermuda buttercup and cape of leaflets illustrated by Michael (1964) sorrel are also mentioned by Howes from six to 13. Most of these were made (1974). from collections around the older town sites and the Perth metropolitan region of Western Australia. b anthers stigmas Figure 1. Mature Oxalis pes-caprae showing bulbs along the thread from parent bulb to contractile organs Figure 2. Variation in leaflets (a) and style-lengths (b) in Oxalis pes-caprae (from Peirce 1973). (from Peirce 1973). Plant Protection Quarterly VoI.12(3) 1997 111 According to Michael (1964) the infesta­ 1979). According to Galil (1968) the spread 1880s, more fruiting material was ob­ tions in South Australia and eastern Aus­ into the Mediterranean was from the earl y tained from eastern Australia (Battye tralia are of one stable 'variety', although introductions into England and western 1913), hence the possibility that more some few years later Alcock (1968) de­ Europe. From there O. pes-caprae gradu­ O. pes-caprae, in particul ar the pentaploid scribed variants from the Eyre Peninsula. ally moved eastwards and was introduced variety, was introduced. The results of In Western Australia, clonal infestations into Israel in the late 19th ce ntury. The these separate introductions are still vis­ are quite common in agricultural aTeas plant is now a weLl established weed in ible today throughout the Swan Valley (Michael 1964, Peirce 1973). lncludingagri­ North Africa (Algiers) (Ducellier 1914), vineyards and a few agricultural infesta­ cultural infesta ti ons, some 33 variants Greece- Crete (Damanakis 1976, Proto­ tions, where distinct vari ants are present have been recognised in Western Aus­ papadakis 1985, Damanakis and Markaki on neighbouring properties. tralia (Peirce 1973). The main leaflet mark­ 1990), and Sardini a (Leoni and Nieddu ings are presented in Figure 2a. 1985). Introducti on into Malta occurred Distribution Within the bulb-forming Oxalis species, about 1810 (Brandes 1991). According to O. pes-cap rae belongs to the group having Magnifico (1984) O. pes-caprae is only a AlIslralia outer bulb scales for protection and inner 'new' weed of importance in Italy. An ac­ Oxa/is pes-caprae is present in all Sta tes and scales for food storage. Of the yellow flow­ count of the spread in the Mediterranean Territories of Australia (Michael 1958, Par­ ered species having flowers borne in false is given by Marshall (1987). sons and Cuthbertson 1992) (Figure 3). In umbels, O. pes-cap rae can be distin guished As in England, Europe and the Mediter­ New South Wales the common pentaploid by: (1) presence of crowded bracts at the ranean, it is probable O. pes-caprae was de­ clone is present in southern coastal towns, base of the umbel of fl owers, (2) stalked liberately introduced into Australia as an south-west slopes and the Riverina area fl owers, (3) a relatively robust habit of ornamental garden plant. The history of (Michael 1964). The distribution for Victo­ growth, (4) rounded (not flattened) leaf the common pentaploid variety and the ria has been given by D.N. McKenzie (per­ stalks, and (5) the presence of a few hairs many tetraploids in Australia is well docu­ sonal communication), Parsons (1973) and on the underside of the leaflets (Clarke mented by Michael (1964). He found con­ Parsons and Cuthbertson (1992). O. pes­ 1934). siderable evidence to suggest that, be­ caprae occurs throughout that State, with Flowers of 0, pes-caprae are tristylic and cause many garden ca talogues contained large infestations present in the Wimmera described as short, mid and long styled illustrations of 0, pes-caprae, or at least a and southern Ma ll ee wheatlands. (Figure 2b), depending on the position of mention of its availability, the introduction The main infestations in So uth Australia the stigmas relative to the two whorls of in most cases would have been intentional. are on the Adelaide Plains, Yorke and Eyre anthers (Michael 1964). The Hackney Nursery in Adelaide, estab­ Peninsulas (Symon 1961, Alcock 1968, According to Michael (1964) the short lished by a former employee of the RJ. Carter personal communication, styled plant with fl ecked lea fl ets, most Loddiges Nursery at Hackney in London, M.J. Catt personal communication). Stride common in Australi a and the Mediterra­ listed 0, pes-caprae under the previous (1960) suggested that dense infestations nean, is a pentaploid (5u = 35). Other vari­ name 0. cem lla in 1845 (Michael 1964). By could cover between 6500 and 10 500 km 2. eties in South Africa (Marks 1956) and Aus­ the 1860s it was recognised as a weed of More recently Rj, Carter (personal com­ tralia (N. Marchant unpublished data) cereals (C larke 1934), O. cern ua was in­ munication) indicated that surveys in 1985 have been identified as tetraploids cluded in a list of plants grown by Si r showed about 8000 km2 of the Eyre Penin­ (411 = 28). William MacArthur at Camden, New sula and west coast of that State to be in­ Baker (1965) also suggested the possibil­ South Wales. Ewart (1907) mentions that fested. ity of existence of a hexaploid (6n = 42) O. pes-caprne was widespread in Victoria, Michael (1964) found many variants of which may have crossed with a tetraploid leading Michael (1964) to conclude that the O. pes-caprae around old town sites in the to fo rm the pentaploid. Although many weed must have been introduced consid­ south-west of Western Austral ia, includ­ tetraploids of different style lengths exist, erably earlier than 1885, when it was first ing paddock inFes tations o f a tetraploid it is thought that the pentaploid as de­ recorded in the National Herbarium of along the Avon Valley near York. A more scribed by Clarke (1934), Meadly (1955) Victoria. Records show that O. pes-caprae recent distribution was g iven by Peirce and Parsons and Cuthbertson (1992), is was recorded in Tasmania in 1865 and (1983), showing infestations of the present only as short-styled plants Queensland in 1875 (Michael 1964). pentaploid va ri ety along the Moore, (Michael 1964). In Western Australia both deliberate Greenough, Avon and Dale rivers. Fur­ There are various keys for identifying and unintentional introductions may have ther infestations are present in cereal and the species of Oxalis in Australia (Black occurred (Michael 1964).