In your task list on Trello can you mark one card as a dependent on another card? For example, you can't put the tree in the ground (task 2) until you've dug the hole (task 1).
We've recently moved the Dependencies Between Cards feature to the main Trello board. That card will be forum for further discussion of supporting this use case.
This isn't a formal way to do this, but you could use some combination of vertical position, comments, and description to achieve the same effect.
We wrote this to help solve the problem for us and then made it free.
There's a free Power-Up that can do that: Card Dependencies for Trello