The richness and heterogeneity of types of ecosystems are the main features of biodiversity in Strumica. This situation is the result of a specific geographical location, climatic, pedological, geomorphological and other features, as well as the changes that have occured in the past geological periods in this territory. In the Belasica Mountain many endemic species of plants can be found, among which the royal fern or Osmunda regalis is worth mentioning.
Osmunda regalis or royal fern is a deciduous fern species originating from North America, and is also present in Europe, Asia and Africa. This plant got the name "royal fern" because it is one of the largest and most impressive ferns in Europe. It grows in forest swamps and river banks, and is also known as floral fern due to the emergence of its fertile grass. It is used in the textile industry.
Royal fern is endemic species of fern which flourishes in a very small space. The surrounding area of the villages of Bansko and Gabrovo is the only place in the country, and perhaps in the Balkans, where this particular species of fern grows in an area of about 500 square meters. Hence, by the decision of the Municipality of Strumica 1987, this plant is treated as a protected species because of its special characteristics that distinguish it from terrestrial plants.