The ability to efficiently select specific aspects of our semantic representations that are relevant for current goals or the context is supported by semantic control processes (controlled semantic cognition framework). This semantic control component is impaired in patients with semantic aphasia, who have multimodal semantic impairment following left hemisphere stroke and are highly sensitive to the control demands of semantic tasks. However, relatively little is known about how this control deficit interacts with aspects of semantic representation. Here we tested whether the relevance of semantic features can influence the demands of control resources in the selection of information within the semantic store in patients with semantic aphasia. Participants performed a feature selection task, where they were asked to indicate which of three features was semantically related to a given concept. We found that patients with semantic aphasia had a greater impairment on low relevance features, suggesting that the selection of target features with low relevance requires greater semantic control than target features with high relevance. Our results confirm the necessity of control processes for the selection of aspects of conceptual knowledge that are only weakly activated within semantic storage when these are task-relevant. The study therefore highlights that semantic cognition emerges from the interaction of control and representational systems.