Gran Bwa means "big tree," and he is the master of the forests of Vilokan, the island that is home to the lwa. He is strongly associated with plants, trees, and practices associated with those materials such as herbalism. Gran Bwa is also the master of the wilderness in general and thus can be wild and unpredictable. Temples often leave a section to grow wild in his honor. But he is also big-hearted, loving, and fairly approachable.
The mapou (or silk-cotton) tree is specifically sacred to Gran Bwa. It is native to Haiti and was made nearly extinct in the 20th centuries by opponents of Vodou. It is a mapou tree that is seen as connecting the material and spirit worlds (Vilokan), which is represented in the courtyard of Vodou temples by a central pole. Gran Bwa is often also seen as a guardian and protector of the ancestors who have always traveled from this world to the next.