Found in the eastern third of Chaco and Formosa provinces and the northeast of Santa Fé is what is described as wet chaco habitat. It consists of small remnant patches of gallery forest (not unlike the Paraná forest), growing by rivers and ox-bow lakes; savannah grasslands studded with caranday palms and "islands" of mixed scrub woodland ( isletas de monte ); and wetland environments similar to those of the Mesopotamian grasslands. The key tree species is the quebracho colorado chaqueño , one of Argentina's four quebracho species, whose name means axe-breaker in Spanish, though it has always been valued more for its tannin than for its hard wood. It can reach heights of 24m, and the most venerable specimens can be anything from 300 to 500 years old. Other common tree species are the urunday; timbó colorado; lapacho negro ; and the intriguing crown of thorns tree ( espina corona ), with clumps of dramatic spikes jutting out from its trunk. On the savannahs, the graceful caranday palms grow alone or in small groups ( palmares ) and reach heights of up to 15m. They are extremely resilient, surviving both periodic flooding and the regular burning of the grasslands in order to stimulate the growth of new shoots for cattle pasture: whereas most shrubs perish in the flames, the caranday seems to flourish.

The wetland swamps are often choked with rafts of camalote , a waterlily with a seductive lilac flower; or the large discs, some more than a metre in diameter, of another distinctive waterlily, the flor de Irupé , whose name comes from the Guaraní word for "plate on the water". Pirí , looking rather like papyrus horsetail, and pehuajó , with leaves like a banana palm, form large reed beds where the water is less deep.