Minecraft wiki entry for Lava, associated text: Flowing lava destroys the following in its path: saplings, cobweb, tall grass, dead bush, wheat, flowers, mushrooms, snow on ground (but snow blocks are immune), lily pads, vines, levers, buttons, all three types of torches, redstone, repeaters, end rods, and rails. Sugar canes hold back lava, but disappear if the sugar cane's water source is destroyed by the lava. Lava also slows down entities, including those that are normally immune to lava damage.