1. We don't need to tell him the truth．
=We needn't tell him the truth.
=We don't have to tell him the truth.
2.The flowers need watering．
=The flowers need to be watered.
3.His leather shoes needs to be mended．
=His leather shoes need mending(主语复数,不加s)
need情态动词：
用于否定、疑问或if从句.
如
Need I do it right now?
No, you needn't.
Yes, you must do it now.
need实义动词,后加宾语.
need后接-ing形式,主动形式,表示被动.
如上面例句.
但在此结构中不用doing
His leather shoes need to be mended by the man.（因为后面有by+执行者）