THE BIOLOGY OF CANADIAN WEEDS .106. LINARIA-DALMATICA (L.) MILL

Dalmatian Toadflax, Linaria dalmatica (L.) Mill. (Scrophulariaceae), i s an important weed of rangelands, agricultural crops and waste areas in North America. The literature is less extensive than for the closel y related yellow toadflax (Linaria vulgaris Mill.). Introduced from Eu rasia as an ornamental plant into North,America by 1894, it became nat uralized in seven Canadian provinces and all of the United States of A merica west of the 100th meridian except for New Mexico. In North Amer ica it ranges from ca. 35 degrees to 56 degrees N latitude and it grow s from near sea level to altitudes up to ca. 2800 m. Production of up to one-half million seeds per plant and its long-lived perennial natur e make the species highly competitive and able to invade cropland and even stands of native ungrazed vegetation. Linaria dalmatica is a hemi cryptophyte with strong vegetative reproduction and dormant seeds. Gro wth of creeping roots after removal of aboveground plant parts limits the effectiveness of control treatments such as grazing, clipping, mow ing or burning. Several herbicides control the species for the short t erm; the smooth and waxy leaf surfaces may hinder herbicide uptake. Ex perimental biological control with insects since the 1960s shows promi se.