Dependency between tasks based on leadtimes

I'm look for an option to make a lead-time/dependency between two tasks. Within our cycles (life plants in this case), we have different tasks that are dependent of each other.

If we sow in one week, we will plant 3 weeks after for example.

We can set it up pre-defined, but I want the related tasks to shift with it, if we change the sowing date for example.