TruncateDendrogram

is an option for DendrogramPlot that specifies the fusion levels at which to truncate the dendrogram.

Valid settings are All, positive integers or a list of two positive integers. The integers should be no larger than the number of clusters. With the default setting All, no truncation is performed.

The setting TruncateDendrogram->n truncates clusters with the smallest fusion levels so that n leaves remain.

Dendrogram truncated such that four leaves remain:

Needs["HierarchicalClustering`"]

Dendrogram truncated such that four leaves remain:

Out[2]=