Top-down vs bottom-up planning
Where the architect might be seen as a master planner, a kind of foreman, who instructs people what to do on a high level. The gardener plans and works on the ground with other gardeners, one gardener might be responsible, but they still work together with and alongside the other gardeners.
Note: top-down is not exclusively architect, and bottom-up is not exclusively gardener! I am simplifying and generalising for the sake of argument. Take everything with a grain of salt.
Bottom-up
Bottom-up planning is less of a fully thought out plan and more of a set of principles for moving forward. We cannot control the outcome entirely, so why should we try to control the process entirely?
It allows for the growth of a project in a semi-anarchic, non-hierarchical fashion. It allows us to bring in a fresh idea, or a new approach late in the project.
And because it spurs ownership between the different parties, it should act as a seed for continued development.
The bottom-up approach to planning is a way of provoking emergence.
Top-down
The top-down approach is usually seen as comfortable and safe, a single entity controls and decides the process.
The approach is not very flexible, but if anything goes wrong you can always blame the architect.
Instead of creating parallell, asynchronous design processes, it often relies on sequential stages where one thing has to be completed before the next work can begin. Is similar to waterfall?
There might be less of a feeling of ownership as in the end, you’re handed a finished product over, instead of being part of working on it.