Leonurus japonicus Houtt. (Labiatae): The Correct Name for a Common Tropical Weed

Abstract

Summary. Confusion is still prevalent over the correct name for the common weedy Leonurus in the tropics; the relevant literature is in Russian. The correct name of the tropical plant previously misidentified as Leonurus sibiricus L. is Leonurus japonicus Houtt. In a paper, entitled "What is Leonurus heterophyllus Sweet?", Krestovskaja (1987) has drawn attention to the correct name of the tropical weed which is more generally known as Leonurus sibiricus. This plant is found widely in tropical Asia, including the Pacific, in Australia and throughout the Neotropics, presumably introduced there from the Old World. Perhaps because most of the recent literature is in Russian, the name L. sibiricus L. is still erroneously used for this plant, except in E Asia, where the change in name has been picked up (Li Xi-wen & Hedge 1994). Because of this, many people have asked us for clarification. It is necessary, therefore, to draw attention to the salient facts. The distinctions between the tropical weed and the Linnean species from Siberia had already been indicated by (Kupryanova 1954). This volume of the Flora of the U.R.S.S. has also been available in English since 1977. Linnaeus based Leonurus sibiricus, first validly published in Species Plantarum, ed. 1, on an illustration in Amman's Stirpium Rariorum in Imperio Rutheno sponte provenientium: 48, t. 8 (1739), drawn from a plant collected in Siberia. There is also a specimen of the same species from Siberia in the Linnean Herbarium (L), LINN 739/6, which Krestovskaja has chosen as lectotype. This choice of lectotype conflicts with the choice of Amman's illustration as type by Kuprianov in the Flora of the U.R.S.S. (1954). In the event, this conflict does not affect the choice of name for the Siberian plant. Both specimen and plate are remarkable for showing the deflexed lower lip of the calyx. An examination of further Siberian material from the Kew Herbarium shows exactly the same character, which is absent from the more widespread ruderal species erroneously called L. sibirica, in which the calyx is smaller, with erect teeth. This and other characters make it clear that there are two species involved. The name Leonurus sibiricus L. must be applied to the Siberian species. In the Flora of the U.R.S.S., the name given to the ruderal species is L. heterophyllus Sweet. This is beautifully illustrated in Sweet's British Flower Garden 1: 197 (1823),