The Euterpe oleracea, Clumping Assai' (I don't find the symbol and accent mark list here.), grows in the flood plain near the mouth of the Amazon, where the base of the palms gets flooded for several months, and in the opposite season gets high and dry. So they are not boggy all year around.
The Euterpe precatoria, Solitary Assai', is from the Central Amazon region. It can grow also in flood plains, but these tend to be hill-country creek valleys, and the palms are often at the lower edges of the hills.
They are all extremely sensitive to cold winds, and are killed in the upper frost temperatures.