may be an issue with generator tip-size. commonly used rotor-stator generators are 7mm to 10mm, which are large enough to process whatever you can fit into a 15mL to 50mL centrifuge tube. I've used a 7mm to grind up morning glory seeds in methanol, in a 50mL tube.
on the other hand, an ultrasonic cell disruptor probe with a half-inch tip may effectively process anything in a 250 to 500mL beaker/flask, an inch probe tip can easily process a liter.
"Nothing is true, everything is permitted." ~ hassan i sabbah
"Experiments are the only means of attaining knowledge at our disposal. The rest is poetry, imagination." -Max Planck