No, some gardens do have a free entrance fee. However, most botanic gardens require a small entrance fee. Often between 1 and 10 euros, they do this because the maintenance of these gardens takes a lot of effort.
In the Netherlands, 27 official botanical gardens are open to the public. These are also all members of the Dutch Association of Botanical Gardens.
'Hortus botanicus' is a traditional name for what is nowadays often referred to as a botanical garden or in Flanders also known as a botanical garden. These are gardens with plants that were used or studied for science. In the strictest sense, a hortus botanicus is a scientific plant collection. An example could be a garden with medicinal herb plants.
A botanical garden is characterized by a diverse mix of plant species, varying from local plants to exotic green plants.
The ANWB voted Hortus Leiden as the most beautiful botanical garden. This garden is not only the most beautiful, but also the oldest botanical garden in Western Europe. This green heart of the city has been there since 1590, when Carolus Clusius, physician and botanist, grew the first tulip collections in Europe.