|January 2002. A legume shrub was found on the side of the road in Palau. It is about 1.5 meters tall. There is a legume shrub was found on the side of the road in Palau. It is about 1.5 meters tall. There is this one shrub, and several seedlings scattered up and down the road in either direction from it. (Cassia obtusifolia is on the Palau plant list since 1982.)
The peanut weed, Senna tora was suggested. It is mentioned on p. 93 of Wayside Plants of the Islands, but there is no photo. If this is it, then it is a apparently a new record for Palau. (Senna is now the name for the genus.)
Others suggested, Cassia obtusifolia (Caesalpinaceae), and this was agreed by consensus. In New Caledonia, it is called “False Pistachio”. It is quite common on the West Coast of the main Island. A reference (in French): Desvals L & P Daly (1997). Guide des principales adventices des cultures mara??ch??res de Nouvelle-Cal??donie, CIRAD-Mandat de gestion, 97 pages.
Cassia obtusifolia=Cassia tora is commonly called a Senna. It is a pan-tropical weed of roadsides, grasslands and cultivated fields, often common near settlements in West-Africa. See IO Akobundu & CW Agyakwa (1987) A handbook of West African Weeds. 521 pp. International Instititute of Tropical Agriculture, Ibadan, Nigeria. It is figured on p. 218-219.
However, it was said that the photograph was not clear enough to distinguish between Senna tora and Senna obtusifoli, which are very closey related and both potentially nasty weeds. It was asked if the weed had sprung up in the vicinity of new roadworks.
The characters used to differentiate between the two species in the field are as follows:
Senna tora: Elongated gland between each of 2 lower leaflet pairs. Anthers rounded at apex.
Senna obtusifolia: elongated gland between lowest and sometimes the next pair of leaflets. Largest stamens with anthers narrowed like neck of a bottle.
The second photo shows some narrowing of the anthers, so it is likely to be S obtusifolia, but it should be checked for this character. Whichever species it is, it is best to remove it before the seed matures.
Later, two other photos were sent to PestNet showing the beaked anthers (above, left & right). The lengths of leaf petioles and pedicels of mature fruit were found to be in the ranges given by respondents. Finally, the leaves have a characteristic legume odor, but I would not describe it as “foetid.” This plant is in a list of Palauan vascular plants (as C. obtusifolia) published in 1980, so it clearly has been here for over 20 years.