Survival of Scotch thistle seed buried at three depths in four New Zealand soils

Abstract

Scotch thistle (Cirsium vulgare) is a stout biennial thistle growing to 15 m tall Introduced more than a century ago and now abundant throughout New Zealand it is mostly a problem in pastures The viability of seed buried for 116 years at three depths was evaluated in four different soils Seed samples buried in nylon mesh bags were removed after 1 2 3 5 11 and 16 years burial and their viability determined by germination in the glasshouse In the 020 mm layer it took from 14 years depending on soil type for the viable seed numbers to fall to 1 of the original amount At the 4060 and 190210 mm depths the amount of viable seed recovered after 16 years burial was considerably greater than at 020 mm Predicted intervals for the remaining viable seed to fall below 1 ranged up to 50 years depending on soil type