This is the normal way to create an asparagus bed, whilst it is possible to use seeds that would take even longer. If you plant the asparagus “crowns” it will take 2 or 3 years to start to get reasonable sized asparagus spears to eat. However once you have an established bed it will crop for up to 20 years. I have a bed I planted around 10 years ago which is still providing me with a good crop every year.