Which of the following is NOT a commonly used type of contract in landscaping?

The choice that is identified as not being a commonly used type of contract in landscaping is a sum-plus contract. In landscaping and construction, contracting methods typically aim to provide clear terms regarding pricing and the scope of work.

Fixed-price contracts outline a set price for the entire project, which gives both parties a clear expectation of costs. Unit-price contracts charge based on the actual quantities of work performed, which is practical for projects where the total scope may fluctuate. Cost-plus contracts allow for reimbursement of costs incurred plus a fee, which provides flexibility when project requirements are not fully defined at the outset.

In contrast, a sum-plus contract does not have a widely recognized or standardized definition in landscaping or construction project management, which sets it apart from the other types of contracts. The lack of common usage and clarity surrounding the term indicates that it does not align with established practices in the industry.