Bamboo – which goes by the scientific name Bambusoideae of the Poaceae family and grows in USDA hardiness zones 5 and 6 – spans an impressive 1,450-some species across 115 genera. From giant bamboo to hedge bamboo to Japanese timber bamboo and everything in between, you'll find an almost overwhelming amount of diversity among bamboo species, but these perennial evergreen plants share at least one thing in common: They're definitely classified as grass, not trees, despite how they appear at first glance.

Tip In spite of an appearance that is very often tree-like, bamboo is officially considered a grass.

Bamboo Species: It's a Grass

Don't feel bad if you've previously referred to bamboo as a tree offhand. In India – a country that is second only to China in terms of growing bamboo – the Forest Act of 1927 legally defined bamboo as a tree, making cutting and transporting it from forests illegal. India Today reports that it wasn't until the Forest Amendment Bill of 2017 that the Indian government finally clarified that bamboo is not defined as a tree.

Science backs up Indian law too. As BioMed Central notes, all bamboo species in the Bambusoideae subfamily are a lineage of perennial forest grasses, which naturally occur on every continent except for Europe and Antarctica. Bamboo does occur, however, in both woody and herbaceous types. It is, of course, the woody type that likely leads to confusion, as these tall, woody plants growing in forest-like clumps appear very much like trees at first glance. Woody bamboo can reach up to nearly 150 feet in height and even features complex vegetative branching just like trees.

These and other characteristics lead many people to casually use the term "bamboo trees," a common misnomer. Herbaceous bamboo, with its shorter shoots, flowering patterns and comparative lack of branching does appear more grass-like to the naked eye. Nonetheless, both woody and herbaceous types of bamboo are indeed definitively classified as grass. On a scientific level, what defines them as such?

What Makes a Grass?

Like all types of grass, bamboo's internodal stem is hollow – in this case called a culm. Bamboo does not have a vascular cambium layer or meristem cells at the top of its culm. A tree, meanwhile, features both a vascular layer and meristem cells. The vascular cambium beneath the bark causes trees to continually increase in diameter over the years, while the meristem cells encourage their ever-growing height.

On the other hand, bamboo does not feature tree-like growth, instead reaching its full height in a single growing season and persistently sticking to its mature diameter rather than expanding. Likewise, bamboo does not feature bark. Instead, leaves form around the culm to offer protection.

That's not to say that bamboo isn't diverse, however. Bamboo culms can grow up to 8 inches in diameter and vary in strength from soft and stem-like to smooth, hard and impressively straight, resembling poles. Some culms even sport thorns. Bamboo also varies in color from green to yellow to nearly black, including instances of stripes and patterns, and sports a huge range of leaf sizes and textures.

Bamboo vs. Trees

Bamboo may be the only type of grass that can diversify into a forest, but for all of its many tree-adjacent qualities, bamboo has plenty of characteristics that clearly set it apart from its woody peers. Even better, most of those characteristics are extremely beneficial, as it turns out.

While not all species grow at the same rate, bamboo growth rate is legendary for a very good reason. In fact, bamboo holds the Guinness World Records title of planet Earth's fastest-growing plant, as some bamboo species grow at rates of about 35 inches per day. Paired with this impressive growth rate is equally impressive environmental sustainability. The growers at Guadua Bamboo in Columbia point out that just under 175 acres of bamboo grove can build about 1,000 bamboo homes per year compared to the 1,483 acres of timber stand required for the same amount of housing.

To say that bamboo is also extremely hardy is an understatement. Some bamboo species can tolerate temperatures of nearly 70 degrees Fahrenheit below zero, while others thrive up to 13,000 feet above sea level, as in the Himalayas and Andes. Compared to timber, a study published in the Journal of Cleaner Production finds that while the yield of bamboo is higher than most wood species, bamboo products have notably less eco-cost than tropical hardwood. Also notable is that a bamboo grove releases about 35 percent more oxygen than an equivalent stand of trees, according to the bamboo producers at Lewis Bamboo.

"Bamboo" That Isn't Even Bamboo

As it turns out, the bamboo tree versus grass rabbit hole goes even deeper. Some plants that go by the name "bamboo" aren't grass, and they are not trees either. In fact, they aren't even bamboo at all.

For instance, heavenly bamboo (Nandina domestica, sometimes called "sacred bamboo") grows in USDA hardiness zones 8 through 10 per the Missouri Botanical Garden, and it sports cane-like stems and leaves that resemble bamboo. However, it is actually a broadleaf evergreen shrub and not a bamboo species whatsoever.

Likewise, the gift shop stable dubbed lucky bamboo or friendship bamboo (Dracaena braunii or Dracaena sanderiana, grown in zones 9 to 12 per the Missouri Botanical Garden) does not even belong to the same taxonomic order as genuine bamboo. It instead belongs to the Asparagaceae family and grows as a herbaceous perennial.

Uses for Bamboo

Back in the realm of "real" bamboo, bamboo's nearly global propagation and immensely long history in addition to its litany of useful built-in features has created a massive list of bamboo uses. Serving in both culinary and medicinal realms, bamboo shoots and juices are edible and offer tons of nutrients, antioxidants, anti-inflammatory properties and fiber alongside little fat or calories.

In landscaping, bamboo can be grown in pots, though it's commonly used as an ornamental plant or privacy hedge. In industry, the bamboo species plays an enormous role, showing up in the construction of everything from homes (with bamboo homes housing over 1 billion people worldwide) to furniture to household accessories as well as lending itself to fibers for weaving numerous textiles found in screens, curtains, mats, clothes and more.