My saplings in minecraft pe won't grow?

I've grown several and they either take forever, or don't grow at all. I tried bonemeal but it's not speeding up the process. Please help. This is minecraft pocket edition.My saplings in minecraft pe won t grow

They don't grow if they are so bunched up together. You have to separate them and then they'll grow. And you also have to be patient they don't grow in 1 second