Fireweed (Senecio madagascariensis
) is a low, upright, short-lived flowering herb that is native to South Africa. It is considered a highly invasive and problematic weed in the state of Hawaii and in Australia. S. madagascariensis
has one or several multi-branches stems with alternatively arranged, narrow, hairless, green leaves.
It produces multiple loosely clustered, daisy-like bright yellow flowers on the tops of it's branches. Each flower has 13 petals. The flowers mature into white thistle-balls which contain up to 150 thistled seeds. The seeds are dry, cylindrical and slender.
All parts of S. madagascariensis
contain hepatotoxic (liver damaging) pyrrolizidine alkaloids. The plants are usually unpalatable to horses, but if not provided with enough pasture grass or hay to graze, they might consume them. Most poisoning cases occur due to contamination of haybales.