An apparatus suitable for controlling vegetation which apparatus comprises a hot-liquid reservoir (28), release means (38) connected to the hot-liquid reservoir (28) and at least one nozzle (74), for applying a stream of foam that contains steam, connected to the reservoir through the release means. The apparatus includes a heating means (34) to keep the liquid hot so the pressure is above atmospheric pressure. The liquid may be pumped by a pump (36) through the hot-water reservoir (28), the water being heated on demand by heaters (34) within the reservoir (28). The apparatus is either propelled by or mounted on a vehicle； and during use of the apparatus to control vegetation the vehicle provides power (24) to the heating means.
