CHARACTERISTICS DISTINGUISHING INVASIVE WEEDS WITHIN ECHIUM (BUGLOSS)

Plant quarantine agencies attempt to regulate the continuing worldwide problem of spread of alien plants, but systems of lant quarantine have not been based entirely on objective criteria. Comparative epidemiological research of known alien weeds may provide such criteria and thereby improve the success of plant quarantine. For this reason biogeographical and ecophysiological data were gathered and analyzed for Echium (Boraginaceae), especially for the three differentially distributed and weedy species in Australia: E. italicum L. (rare), E. vulgare L. (uncommon), and E. plantagineum L. (common). Such data included the following native distributions in Eurasia and North Africa, historical spread in Australia, seed germination, vegetative growth and propensity to flower. Quantitative plant characteristics which distinguish weedy species of Echium from their innocuous counterparts, and whose values could most easily be determined by plant quarantine officials, are the breadth of native distribution and rapidity of seed germination. Although these results were derived from only a few temperate taxa, they may apply on principle to many species.