Factors affecting seed germination of little mallow (Malva parviflora) in southern Australia

Little mallow is becoming an increasing problem in no-till farming systems in southern Australia. There is little known about the germination ecology of this species, making management of the weed more difficult. Experiments were conducted to determine the effect of different factors on seed germination. Freshly harvested seeds had high levels of innate dormancy with only 5% of seeds germinating. Germination increased with storage time but did not reach more than 47% even 13 mo after seed harvest. Germination was not influenced by light. Germination was stimulated by scarification, which indicates inhibition of germination in this species is mainly due to the seed coat. Germination was moderately sensitive to salt and osmotic stress. Germination was completely inhibited at osmotic potentials of -0.6 to -1 MPa. Seeds of little mallow germinated over a broad range of pH between 4 and 10, but germination declined at higher pH. Potassium nitrate at 0.005 M stimulated seed germination of scarified seeds to a maximum level of 76%. Seedling emergence of little mallow was greatest at burial depths of 0.5 to 2 cm. No emergence occurred at 8 cm or deeper. Greater emergence in response to shallow burial and the requirement for scarification may both contribute to the increasing problem of small mallow in no-till farming systems in southern Australia by delaying emergence until after the crop has been sown.