Dense vegetation covers 0.6km2 of Lokrum’s total surface area of 0.7km2. One can find in a single location and a small area all natural development stages of plant communities in the Mediterranean region of Europe, and is therefore protected as a Special Reserve of Forest Vegetation since 1976.
In order to protect diverse plant communities which are not of natural origin (olive groves, gardens, promenades, the botanical garden), human influence is indispensable for the proper management of the Reserve.
The plant community, mostly under the influence of climate, to which inclines the natural development or vegetation climax on Lokrum is the FOREST OF EVERGREEN OAK AND FLOWERING ASH. Since the forest was heavily logged in the past due to its high quality wood material, most of the island is today covered by its degradation stages: coppices and impassable macchia.
The next stage of the forest degradation is garrigue, an open shrubland where low woody species dominate (heather, black locust, rockroses, rosemary, prickly juniper). There are also several types of the final stage of degradation on the island, such as the rocky grassland. The island’s vegetation on rocks, dry stone walls and coastal reefs, as well as weeds, is also interesting.
Taking into consideration the small surface area of the island, it hosts a relatively large number of plant species, a total of 400 species. The evergreen oak (Quercus ilex), which can grow up to 20 meters high and live a thousand years, stands out among trees and shrubs.
Several truly impressive exemplars of the evergreen oak grow on Lokrum, for example, near the Lazaret.
Laurel (Laurus nobilis), the holy tree of Ancient Rome and Greece, the symbol of fame, wisdom and recognition, flourishes on the island, which indicates a relatively large quantity of precipitation.
Myrtle (Myrtus communis) is a fragrant, decorative plant with blue berries which doesn’t respond well to low temperatures. It’s a close relative of the Australian eucalyptuses grown in the Botanical Garden, and its branches were once upon a time used for basket weaving and fishing traps.
Strawberry tree (Arbutus unedo) has white bell-shaped flowers in the fall and winter. It produces tasty berries, which can knock out a person when eaten in larger quantities.
Terebinth (Pistacia terebinthus) is an evergreen shrub or tree which excellently holds up to heat, drought and salt, and is ideal for planting near the shoreline. It was previously used for tanning skins and dyeing fish nets.
Stone pine (Pinus pinea) is a twenty meters high pine tree with a strong trunk, characteristic umbrella top and edible pine nuts. The tree’s bark is red-brown and deeply fissured into broad vertical plates. The Aleppo pine (Pinus halepensis) was probably brought to our shores by the ancient Greek, and ever since then it flourishes in the central and south Dalmatia.
The Aleppo pine forests in Croatia (and on Lokrum) are not autochthonous but are wild and can survive without human help. The forests are beautiful but also, unfortunately, burn easily: burning pine cones can fly through air for more than ten meters and thus spread the forest fire.
Besides the woody plants which dominate Lokrum, climbing plants such as honeysuckle, ivy, Mediterranean similax and cleavers also grow in forests and macchia.
Some of the Lokrum plants belong to a group of rare and protected species of Croatian flora, and can be seen in the Botanic Garden.
Jupiter’s Beard (Anthyllis barba-jovis) is a silvery and hairy evergreen shrub up to 3 meters high, with silvery and silky leaves and pale yellow flowers with round heads. According to the Red Book of Vascular Flora of Croatia from 1980, it’s a rare species and protected in all natural habitats.
Joint fir (Ephedra campylopoda) is a very „primitive“ and sensitive species of Croatian flora with articulated branches which hang from the trees it climbs.
Tree spurge (Euphorbia dendroides) grows in the cracks of steep and unapproachable cliffs to the south. It is evergreen in every sense of the word: it flowers and sprouts leaves in the winter and during summer droughts completely loses them, which is quite rare for our region.
Stinking madder (Putoria calabrica) is a species growing on steep sea cliffs and walls (e.g., on the walls of Fort Royal) with small pink flowers in the fall. In the Dubrovnik region it reaches the north-eastern border of its distribution and can be considered a rare species.
The biodiversity and the unique climate of small Lokrum were first noticed in ancient times, but the idea to establish a special acclimatization institute which would study the adaptation of foreign plants came into being only at the beginning of the 20th century.
The plan began to be implemented in 1959 when on a surface area of about 2 hectares – what used to be an abandoned monastery estate with a vegetable garden – the BOTANICAL GARDEN was established and first exotic species were planted.
Today, about four hundred species from Australia, South America, Africa and other parts of the world as well as the protected and endangered species of the wider Dubrovnik region flourish here.