Curves can also be a response to what is planted. I’m a big believer in planting for purpose. Often the planting composition that is put together to affect a structure or a space. I like to make planting beds fit a planting rather than use plantings to fill pre-formed beds unless there is a compelling reason to do otherwise (such as to purposely create a rectilinear layout). That often results in gentle curves.
I find that the need for curves or lines usually evolves based on what is going on with site features, circulation, and how plants are used. I seldom, if ever, decide that a design is going to be curvy or square from the get go unless it is driven by a major feature (like a pool preference conveyed by the client) or physical site constraints (wetlands or lot shape vs. house shape)..
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