  We explore correlations harvesting by two static detectors locally
interacting with vacuum massless scalar fields in the presence of an infinite
perfectly reflecting boundary. We study the phenomena of mutual information
harvesting and entanglement harvesting for two detector-boundary alignments,
i.e., parallel-to-boundary and vertical-to-boundary alignments. Our results
show that the presence of the boundary generally inhibits mutual information
harvesting relative to that in flat spacetime without any boundaries. In
contrast, the boundary may play a doubled-edged role in entanglement
harvesting, i.e., inhibiting entanglement harvesting in the near zone of the
boundary while assisting it in the far zone of the boundary. Moreover, there
exists an optimal detector energy gap difference between two nonidentical
detectors that makes such detectors advantageous in correlations harvesting as
long as the interdetector separation is large enough. The value of the optimal
detector energy gap difference depends on both the interdetector separation and
the detector-to-boundary distance. A comparison of the correlations harvesting
in two different alignments shows that although correlations harvesting share
qualitatively the same properties, they also display quantitative differences
in that the detectors in vertical-to-boundary alignment always harvest
comparatively more mutual information than the parallel-to-boundary ones, while
they harvest comparatively more entanglement only near the boundary.
