Generally,the best time to prune is in late winter, before spring growth starts.

VOA: special.2009.10.06

I tie a spring to my back and I anchor it to the wall and see how much the spring stretches before the two forces balance.

我把弹簧一端系在背后,另一端固定在墙上,观察两个力平衡时弹簧的伸长量

耶鲁公开课 - 基础物理课程节选

Growers can plant the roots during spring before they develop buds.

VOA: special.2009.04.07

Before spring training, Rodriguez admitted to using steroids while he played with the Texas Rangers in 2001-2003.

VOA: standard.2009.12.24