Complex sentence: Most'Snowdrop Gardens' will have the common Galanthus nivalis snowdrop, but some have more unusual snowdrops, some which may be unique to the garden that they are growing in and the rarest may only survive in that garden due to the conditions and environment.
Split into simpler sentences: Most'Snowdrop Gardens' will have the common snowdrop, "Galanthus nivalis", but some have more unusual snowdrops, some which may be unique to the garden that they are growing in. The rarest may only survive in that garden due to the conditions and environment.