Flood growth pods

Flood Growth Pods are large, spherical collections of biomass that grow on the surfaces of ships, buildings, and other structures. They are started when mass Flood forms enter an area, or when Flood Spores enter the area. They incubate developing Infection Forms. They are only seen during stages of advanced Flood infestation when a Gravemind has formed and consumed enough flesh, to support Pure Forms. They have no forms of attacks, but if they are attacked, they explode and release their infectious spores and their Infection Forms. They tend to release about 25 Infection Forms if shot at or if hit by the blast from an explosion in their immediate vicinity.

They are first seen in Halo 2, during the Flood Invasion of High Charity, though it was only at development stage. Later in Halo 3, it was encountered more in the Campaign levels Floodgate and Cortana, and in the multiplayer maps Isolation and Cold Storage, though the multiplayer pods do not release infection forms.

The use of Flood Growth Pods, is quite similar to Carrier Form Flood, they incubate the Infection Forms for a certain time and if the pods are agitated (i.e. being shot) they burst open and spew Infection Forms (between 5 and 20 Infection Forms). Unlike the Carrier, however, the pods are completely idle and mostly defenseless. They can't suicide bomb the player like a Carrier can either, but still pose a threat due to the large number of Infection Forms they release.

Halo Wars

 * Flood Growth Pods now serves as double-edged knives: shooting them will sometimes releases precious resources for weapon and vehicle upgrades. But other times, they will release a swarm of Infection Forms that can infect unprepared infantry in seconds.

Trivia

 * You can sometimes hear the scream of a Combat Form when you break a Growth Pod on Isolation.