Ferroseed is a small oval-shaped metallic Pokémon that resembles a spiked acorn. Ferroseed have three horizontal black lines encircling it, and many sharp green thorns covering its body. Its eyes are yellow and have green rims around them.
Ferroseed can shoot a barrage of spikes from its body when attacked, allowing it to flee by rapidly rolling away.
They are also the only Grass type Pokémon immune to Poison attacks.
Ferroseed appears to be based on cockleburs, durians, or seeds from horse-chestnut trees or datura, all of which are known for their rough, durable skin and sharp thorns. Due to its Steel-typing, it may also be based on a mace.
Ferroseed’s English name is a combination of ferrum (Latin for iron) and “seed”.
Its Japanese name, Tesseed, may be a combination of 鉄 tetsu (iron) and seed.