The red flower is fire, the ultimate weapon of men and the thing the jungle animals fear so much they will not even name it. Bagheera tells Mowgli that he must get some and take it to the Council at the Rock, so that he can use it to protect himself, saying,
Go thou down quickly to the men’s huts in the valley, and take some of the Red Flower which they grow there, so that when the time comes thou mayest have even a stronger friend than I or Baloo or those of the Pack that love thee. Get the Red Flower.
Mowgli actually finds it very easy to procure the fire, of which he alone is not afraid. Bagheera tells him that it grows in little pots, and when Mowgli goes to the village, he soon sees a child pick up a fire-pot and fill it with red-heart charcoal. When the child takes the fire-pot outside, Mowgli simply snatches it from him and makes off with it, while the child cries with fear.
Mowgli quickly comes to understand much about the nature of fire, realizing that he has to keep the fire-pot full of twigs and bark in order to feed the fire and keep it alive. However, he does not know enough about fire to be afraid of it, never having been burned and only having found the fire "warm and pleasant" when he used to lie beside it. He is, therefore, able to wield the fire as a weapon without fear when the time comes for him to do so.