The Blastcap is a mushroom-like plant which is native to the planet Tallon IV. They can be found in the Tallon Overworld and Chozo Ruins areas. They resemble large capped mushrooms and they come in small and large sizes and also live in groups.
The spores of the Blastcap can survive in outer space, and have propagated throughout the galaxy by means of traveling on interstellar solar winds. When approached, they will make a rustling noise and shake violently. Upon contact with Samus, or when sufficiently damaged, they will explode. The explosion will damage Samus as well as release a cloud of gas as the mushroom itself is consumed.This can also often set off other nearby Blastcaps in a chain reaction effect. Contrary to its scan data, the gas is not harmful to Samus.
A more brightly-coloured breed of Blastcaps are also encountered in Metroid Prime Hunters on both Alinos and Arcterra. The gas emitted by this variant when destroyed can harm Samus, and will fill a small area for a short time around where the Blastcap was. The type that appears on Arcterra seems to be a white arctic species, though they appear to be merely scenery in the Frost Labyrinth and cannot be scanned. If a hacking device is used, the Arcterra variant shares the same scan, and emits the same gas if destroyed. The only difference is that another Blastcap will grow back after the gas clears up.
In Metroid Prime, Blastcaps can be found in these rooms: Tallon Canyon, Watery Hall, Waterfall Cavern, Meditation Fountain, Ruined Gallery, Gathering Hall, Watery Hall Access and Transport Tunnel C. In Hunters, Blastcaps are located in High Ground, Alimbic Gardens, Crash Site and Frost Labyrinth.
- A similar species of mushroom known as "Blaxcaps" appears in the first Pikmin game during the final battle with the Emperor Bulblax.
- An unused Phazon variant of the Blastcap exists in the code of Prime. It appears to be unfinished, as only the cap of the mushroom is different, having a blue color.