The forests of Mljet mostly consist of the Aleppo pine and are among the most beautiful and most preserved forests of that type in the Mediterranean. Mljet is also the home of numerous endemic plants such as the Dubrovnik cornflower (Centaurea ragusina) and tree spurge (Euphorbia dendroides). The forests which are especially dense in the area near Veliko and Malo jezero go all the way down to the sea and are in perfect harmony with it. The shrubland consists mostly of evergreen and nearly impassable shrubs. In addition to forests and shrublands, there are other habitats such as coastal sand dunes, steep and high cliffs and plants growing on coastal reefs.

Almost 90 % of the total surface of the National Park is covered in forests. The majority of the forest surfaces are Aleppo pines (Pinus halepensis), brought to the island in the Greek times. This tree can grow up to 20 meters in height, and the trunk and branches are often curved. The treetops are spherically pyramidal, and it grows irregularly in old age. The bark has a greyish color. When the tree is still young it is smooth, and later it becomes red and brown with creases. The buds are elongated and cylindrical with free dark shells with white rims. The buds are not covered in resin. The needles are bluish green to light green. The Aleppo pine trees are widely present in the Park, especially in warm and sunny areas.

Another forest type are the holly oak and manna ash forests (Orno-Quercetum ilicis). The holly oak is a tree with a broad and spherical treetop, dark grey and jagged bark and leathery dark green leaves. It grows acorns. The most significant preserved localities are Velika dolina, Valakija, Planjak and Knežepolje.

Certain forms of vegetation are developed by way of degradation of the aforementioned forests, such as shrubland, garrigue and rocky grounds. The holly oak is often accompanied in Mljet shrublands by evergreen broadleaved plants such as the strawberry tree (Arbutus unedo), mock privet (Phillyrea media), tree heath (Erica arborea), mastic (Pistacia lentiscus), common myrtle (Myrtus communis) and laurestine (Viburnum tinus), and occasionally carob tree (Ceratonia siliqua), wild olive (Olea oleaster) and bay laurel (Laurus nobilis).

Regarding conifers, the local shrublands have the prickly juniper (Juniperus oxicedrus) and Phoenician Juniper (Juniperus phoenicea). The strawberry tree is an evergreen bush or a small tree that grows up to 10 meters in height. Its fruit is called ‘maginje’ and its leaves are reminiscent of laurel. Its green and white flowers grow in lush and beautiful clusters. The fruit is orange-red and round. It is interesting to note that the fruit and flowers appear at the same time. The fruit of the plants in this locale is very rich with vitamin C. The leaves can be used as spice instead of laurel.

Some other important plants on Mljet are:

Madder (Rubia spp.) – a genus including 38 species, with the common madder (Rubia tinctorum) the most famous. The name stems from the Latin adjective of ruber (red) because the roots of the plant are often used for red paint for textile, most frequently wool. Madder is a perennial herbaceous or semi-woody climbing or clambering plant, and it most frequently has evergreen leaves.

Black bryony (Tamus communis) – perennial twining plant from the family of Dioscoreaceae. It can grow up to 2-4 meters in height.

Gum rockrose (Cistus ladanifer) – small bush with large white flowers which resemble cups. In its leaves, the plants has oleoresin called labdanum and essential oil obtained by distilling leaves and branches. The oil is used for aromatherapy and in the perfume industry.

Sage (Salvia officinalis) – perennial semi-bush plant up to 30 – 60 cm of height and with a strong root. The lower parts of the stalk are woody, and the upper part is herbaceous. The leaves are long and oval and the flowers are dark purple. It is both wild and domesticated. It is used in medicine and as a spice.

Laurestine (Viburnum tinus) – bush up to 3 meters in height with darkgreen leaves. Has clusters of small white flowers. The fruit is a 3-4 mm long, single seed, narrow, ovoid, but stiff near the top, shiny metallic dark blue stone fruit ripe in fall. The seed is oval and bluish with irregular creases.