Yucca

I keep threatening to destroy this Yucca.  For 11 months of the year it is an eyesore with straggly tatty leaves that have vicious spikes on their ends that stab you in unmentionable places when you back into them.  Then, out of the blue, it sends up a colossal flower spike covered in these spectacular blooms and all is forgiven.  This flower spike is about 8ft (2.5m) tall.