Notocactus graessneri flaviflorus
(This plant comes in a 3.5" pot. You will receive a very similar plant to the one in the picture. It may or may not be blooming at the time of your purchase. The plant is shipped in its pot to prevent any damage to the roots).
This is a medium- sized solitary, fast growing cactus closely resembling to Parodia haselbergii and also from southern Brazil. It distinguish for its yellow blooms.
Flowers: Small yellow, up to 2,5 cm long and 2 cm wide and each can last one to three weeks. Petals semi-erect spreading and not closely surrounding the style, the stamens visible. Tube relatively long with clusters of bristles and some wool. It is self-sterile.
Blooming season: It flowers at the end of the winter or in early spring for a long period of time (It can last blooming to two months!). Will start flowering around 5 cm in diameter.
Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz