What advise grandfather gave to Rakesh

This Question is given from a book published by Author Ruskin Bond named "The Cherry Tree".

In this, a boy named Rakesh burrowed a cherry seed in his Garden and was usually very eager to know how fast will the cherry Tree will grow.

He was offered a bunch of cherries when he bought them at a local bazaar, most of them were eaten by him, he gave only one cherry to his Grandfather.

Making him leave with those cherry seeds after eating the delicious pericarp (or outer fruit covering) and endospermic flesh (the inner part).

Rakesh kept the seeds obtained from the cherry to himself, after slowly chewing and carefully removing them.

It was His Grandfather who made a suggestion to not keep, but , sow or bury them into the soil to acquire their benefits later on , and grow into a big cherry tree.

By then he picked up a spade made up of metal and started to bring about a hole by digging into his Grandfather's garden , to his shock , Rakesh's Grandfather had already grown or put some mustard seeds.

Seeing this he found a perfect place or a dark corner were no adverse climate would worry those cherry seeds , without his metallic spade he directly pushed down (the seed) by the help of his thumb until it was sown into the soil.