Matter produced by plants or growing in the manner of a plant WordNet 3.0 & Open English WordNet

Biomass refers strictly speaking to the total weight of all the living things in an ecosystem. However, it has come to refer to the amount of plant and crop material that could be produced in an ecosystem for making biofuels and other raw materials used in industry, for example. OmegaWiki

Vegetation used as a fuel, or source of energy, especially if cultivated for that purpose. Wiktionary

Vegetation used as fuel. Wiktionary (translation)