But what is fireweed? The botanical name for fireweed is Senecio madagascariensis and if you didn’t know any better it could just be overlooked as a normal weed with a pretty yellow flower, something like a dandelion. It is a small weed that grows to 50cm in height and in dry or harsh conditions it will often only reach 20cm. The leaves are bright green, narrow and about 2-7cm long. The flower is small (1-2cm in diameter), yellow, has 13 petals and found in clusters at the end of each branch. Each plant can have anywhere up to 200 flowers.