The south-facing exposure of the northern slope of the botanical garden has made it possible to accommodate some of the species that characterise the coastal strip of the Trieste Karst in this part of the garden. In this area, the vegetation is dominated by Mediterranean scrub, represented in particular by the holm oak (Quercus ilex). 

The Karst in the Trieste area is characterised by the meeting of two climatic zones. Along the coastline, characterised by high cliffs, the Mediterranean climate is expressed at its northernmost point, which fades into the cooler Illyrian-Continental climate beyond the ridge. This coexistence of factors is reflected in a plant composition that includes evergreen species typical of the Mediterranean coastline such as bay laurel (Laurus nobilis), broad-leaved phillyrea (Phillyrea latifolia), laurustinus (Viburnum tinus), wild madder (Rubia peregrina), and Etruscan honeysuckle (Lonicera etrusca), to thermophilous deciduous species from the Balkans such as the common hop-hornbeam (Ostrya carpinifolia), manna ash (Fraxinus ornus), and Montpelier maple (Acer monspessulanum).  

On the sea cliffs of the Trieste coastline, the absence of a terrigenous substratum and the exposure to winds and salinity create an environment that is poorly suited to tree growth. Therefore, these environments are characterised by low vegetation mostly composed of endemic species such as the Adriatic bellflower (Campanula pyramidalis), the yellow germander (Teucrium flavum) and Wulfen's spurge (Euphorbia characias subsp. wulfenii). Also characteristic of these environments are aromatic and/or thorny species such as common sage (Salvia officinalis), terebinth (Pistacia terebinthus), myrtle (Myrtus communis), Christ’s thorn (Paliurus spina-christi) and spiny asparagus (Asparagus acutifolius).