The Bambusoideae is a subfamily of the true grassfamilyPoaceae, and is characterized by having 3 stigmas and are mostly tree-like. However, there are uncertainties at practically every taxonomic level within the Bambusoideae, and different types of data (floral morphology, vegetative structures, anatomy, and genetics) often result in support for differing relationships.
The Bambusoideae generally consists of a distinct “core” group of genera, the woody bamboos (Bambuseae) and an associated group of genera of questionable affinity, the herbaceous bamboos (Olyreae). The bambusoid taxa have long been considered the most “primitive” grasses, mostly because of the presence of bracteate, indeterminate inflorescences, “pseudospikelets,” and flowers with three lodicules, six stamens, and three stigmas.
Phylogeny of the bamboos within the BEP clade of grasses, as suggested by analyses of the whole of Poaceae and of the bamboos in particular.
Following molecular phylogenetic research, many tribes and genera of grasses formerly included in Bambusoideae are now classified in other subfamilies, e.g. the Anomochlooideae, the Puelioideae, and the Ehrhartoideae. The subfamily in its current sense contains three main clades, classified as tribes. These distinct lineages strongly correspond with geographic divisions, representing the New World herbaceous species (Olyreae),tropical woody bamboos (Bambuseae) and North temperate woody bamboos (Arundinarieae).
^Kelchner S, Bamboo Phylogeny Working Group (2013). "Higher level phylogenetic relationships within the bamboos (Poaceae: Bambusoideae) based on five plastid markers". Molecular Phylogenetics and Evolution67 (2): 404–413. doi:10.1016/j.ympev.2013.02.005. ISSN1055-7903.