Snow-in-summer is a common name for several different plants:
Cerastium tomentosum, a low-growing flowering plant of European origin
Melaleuca alternifolia, the Australian tree from which tea tree oil is obtained
Melaleuca linariifolia, also known as the narrow-leaved paperbark and flax-leaved paperbark
Vriesea 'Snow In Summer', a hybrid cultivar of the genus Vriesea in the Bromeliad family.