For more than 50 years the effect of heat on the germination capacity of weed seeds has been studied intensely.
Studies consider the effect on wet as well as dry seeds of different weed types, in which they were exposed to dry as well as humid heat such as hot steam for different durations. Studies made at the University of Zurich in the fifties of the last century showed clear results:
While dry heat did not yield a sufficient desired effect on seeds, humid heat such as hot steam ensured the complete killing of all seeds at 95°C after 5 minutes of treatment.
Dry heat even proved to be counterproductive: Germination capacity of weed seeds was even found to improve at times.
Hot steam showed to be the most thorough and effective means to treat against weed seeds and is superior to all other thermical methods as well has chemical herbicides, which are only partially effective against seeds.
