I specialize in purely stump grinding. I use plywoods for cover to ensure no windows break because when i use my stump grinder, chips start flying everywhere at a fast speed and it's just common sense. Pine,elm,eucalyptus,redwood and maple are common. -Easiest stumps to grind are palm because they have alot of water inside. -Oak Stumps are super tough! However they can be grounded out.