Graham Oakes replies: All wood species can be used for end grain bowls. Exotic woods will be difficult to use but can be done. The wood species is less important than the technique used to hollow the bowl. The cells in a piece of wood look like a bundle of straws facing up the tree. When cutting cross grain you are cutting the sides of the cell walls when using a push cut, which cuts quite nicely. When cutting end grain, you are trying to cut the ends of the cells while using a push cut. This causes tear out and vibration.
The thing to do when doing end grain bowls is to use pull cuts or back hollowing techniques to hollow out the bowl. You will get very nice cuts on the bowl by making a small depression in the middle of the bowl and then working outward to the rim of the bowl. This should be repeated until the bowl is at the desired thickness. This is completely opposite from standard bowl turning techniques but this is what is needed for end grain bowls.
One more point for end grain turners is to try turning green wood very thin. I have done this and have had many bowls not crack on me. The key is to go for 1/8˝ wall thickness or thinner and use straight grained non-porous wood. Happy Turning.