The vegetation of northern Latium has particular characteristics. Its volcanic soils on hilly and flat land are favorable for agriculture, and, in the case of the Vico territory, for hazelnut monoculture. Extensive areas are forest, often original and prevalently coppiced, with turkey oak and chestnut. Diverse bioclimatic, oceanic and continental influences converging in Latium have made this region a mixed arena of European mesophytic union (type of plants in temperate climates and in soils of average humidity), and subtropical , with atlantic elements, and, at higher altitudes, with oriental-balcanic elements.

From the post-glacial period the climate of this zone is characterized by:
- an atlantic period dominated by mixed forest reaching 60%; now it’s a relict concentrated in small nuclei in the plains (5,500-2,500 b.C.);
- a sub-boreal period, dry heat, where bay oak substitutes mixed forest. Now bay oak regresses in favor of turkey oak (2500-800 b.C.);
- a sub-atlantic humid cold period in which forests descend to lower levels and beech takes the place of bay oak (from 800 d.C. to the present);
- according to the scholar Padula, continental is taking over the climate. This means that any possibility of recreating its natural origins is more remote.

This profound change in forest typicality is attributed to human settlements in the last 2/3000 years especially in Sabatine territory. The original great forests were constantly being modified and reduced. Some traces can be noted above Mount Rocca Romana, in Manziana’s territory and along the slopes around Lake Martignano. Forests in the Lake Bracciano watershed, subject to periodic cutting, offer little of interest from the naturalistic point of view, although a fascinating landscape for tourists. Pockets of Mediterranean scrub contain ancient forest of holm oaks, oak and shrubs such as bay, cane apple, and elm.

This profound change in forest typicality is attributed to human settlements in the last 2/3000 years especially in Sabatine territory. The original great forests were constantly being modified and reduced. Some traces can be noted above Mount Rocca Romana, in Manziana’s territory and along the slopes around Lake Martignano. Forests in the Lake Bracciano watershed, subject to periodic cutting, offer little of interest from the naturalistic point of view, although a fascinating landscape for tourists. Pockets of Mediterranean scrub contain ancient forest of holm oaks, oak and shrubs such as bay, cane apple, and elm.

Potential species

According to actual climatic conditions, potential species for mixed natural forest are Quercus cerris, Carpinus betulus, Ostrya carpinifolia, Corylus avellana, Pyrus piraster, Sorbus torminalis, Coronilla emerus, Acer campestre ed obtusatum, Cornus, Evonymus, Ligustrum vulgare, Laburnum, lime, cherry, and elm; above 500 meters also Fagus abies.

Forest cover

The territory of Anguillara Sabazia, Bracciano and Trevignano Romano has about 2,300 hectares of forest, for the most part coppice.
Chestnut prevails - over 50% - -followed by turkey oak, manna ash, hornbeam, pubescent oak, holm oak and some beech.
On the northern sector of the watershed, the Odescalchi estate has 1,550 hectares of forest cover, and Vicarello 425 hectares.
The Martignano watershed has about 100 hectares of forest.
Agriculture in the Lake Bracciano watershed is less than 200 hectares.

Manziana forest
The Great Forest of Manziana and La Caldara are situated between the Tolfa mountains and Lake Bracciano, both of great importance to the natural environment. La Caldara possesses a rare colony of birch, unique in central Italy, of unknown origin but perfectly adapted to the natural habitat of the area. The Great Manziana Forest, rather rare also, of original turkey oak, that is, not coppiced, in gigantic tall columnar trunks giving us an idea of what the primordial forest landscape was. In addition to turkey oak, other trees in the forest are Italian oak, mountain ash, and maple.

Rocca Romana forest
The highest mountain within the territory of Trevignano Romano, Bassano Romano and Monterosi is Mount Rocca Romana (612 meters). Its forest vegetation is subject to periodic cutting. Its main species are chestnut, turkey oak, hornbeam and some beech.
Beech Fagus Abies that grow here are part of a vast forest which from Tuscany reached all the way to Rome, in epochs when the climate was colder than now. It adapted to successive climate changes; in fact, it grows here in a lower altitude than its norm. On the Sutri side, beech is found at 500 meters, while its norm is from 700 to 1,200 meters. Notwithstanding its vigorous growth, it’s a relict of ancient forests covering a vast geographical area, conserved thanks to the “oceanity” of the climate. This phenomenon can also be observed in Tuscany (Amiata, Cetona), Latium Appennines and central-north Italy. This is due to a pluvious factor congenial to this species.
Between Manziana and Bracciano, and Trevignano and Sutri, and among the Martignano forests, small and medium shrubs grow such as blackthorn, wild rose, hawthorn, blackberry and ivy. Among wild orchids the most common is Cephalanthera along the borders of scrub.
In the Vigna Grande and Martignano forests a discreet amount of wild strawberries could be found. Between April and August, cyclamens, wild pansies, forget-me-nots, some forest hyacinth (characterized by blue hanging flowers), elleborine rosea, blueberry (edible), white anemone, wild carnations and many others. Many wild plants which were once common are now rare or disappeared, because they were uprooted while being picked. These plants in our list are now protected by national laws. Wild-flower picking is extremely harmful to the species.