They beat us differently in the spring. Instead of the dull pain of a winter strap, there were these new green switches that lost their sting long after the whipping was over. meaning?

This is a passage from the The Bluest Eye by Toni Morrison during chapter 6. In this passage the speaker remembers the spring and associates it with the beating that he would receive during that time. Where they would beat him with green switches (form of branch) that would still hurt long after the beating was over. This memory and association caused a very specific pain when thinking about summer.