The ball of vines seen in guidebooks and artwork alike to represent this pokemon is far from the most common shape of Tangrowth in the wild; it is, however, by far the easiest to draw. Tangrowth withdraw their many stems into this form against strong opponents to give themselves maximum defense in battle. But wild Tangrowth do not often battle; they spend most of their time lying in wait, disguised as the patches of tall grass which wild pokemon call home.
Tangrowth take this grassy form to lure in prey. Rattata, Bidoof, and other extremely common grass pokemon have learned to avoid them, using senses far stronger than those possessed by humans; it is rarer and often migratory pokemon, less known to Sinnoh's tall grass, on which these creatures usually leech. The prey is not killed for so long that some have proposed classifying Tangrowth as parasites, not predators; rather than eat them at once, they slowly absorb their energy.
There are two ways to detect a hidden Tangrowth. The first is to rustle them with wind, typically by riding one's bicycle past them at full speed; the many tangles these pokemon possess cause them to shake and rustle far more easily than true grass. This method is frequently used by Sinnoh pokemon trainers in search of rare pokemon, who are often ensnared by Tangrowth. The second is to attempt to cut through them, for unlike grass, Tangrowth fight back. They are the enemies of lawnmowers and Scyther, and show no mercy to either.