When selecting a tree headstone, material durability is paramount as it will be exposed to outdoor elements indefinitely. Granite is the industry standard due to its resistance to weathering, acid rain, and temperature fluctuations. Ensure the supplier uses Grade A natural stone without cracks or large inclusions. For a more 'natural' look that blends with a tree setting, basalt or river boulders are excellent choices, but they must be deep-etched to ensure inscriptions remain legible over decades.