A new model of blue jets is proposed. A blue jet consists of an upward propagating leader whose top part is seen on photos as a "trunk of a tree", and is capped at the top side of the leader by its streamer zone. The latter is shown as tall and narrow branches of "the tree". It is shown that blue jet streamers can be sustained by relatively moderate cloud charges due to upward transfer of the high thundercloud potential by the leader. The streamer length is estimated along with the height at which the streamers can reach the ionosphere. The propagation of a streamer in the atmosphere of exponentially falling density N is computed. It is found that the critical external field ES required for unlimited streamer growth satisfies the similarity law ES/N ~ const. Shortcomings of the existing blue jet models are discussed.