Tremalzo is an extraordinary botanical garden thanks to its concentration of endemic flowers and it is best known in all Europe for many botanists.
In the area of Tremalzo there is also the pass Bocca Casèt, famous for the bird migration during the summer and autumn time.
Tremalzo is the name of the mountain group located in the south-west part of Valle di Ledro, along the old border line between Italy and Austria, now the border between Trentino and Lombardia.
The pass is 1,665 m above sea level but the highest point is Monte Tremalzo peak at 1975 m. Other mountains which belong to Tremalzo are Cima Marogna (1,953 m) which looks towards Lake Garda, Corno Spezzato (1,858 m) facing the valley and Cima Avez (1,895 m) on the west side. In summer the climate becomes milder thanks to the influence of Lake Garda, while in winter it snows a lot and the thick blanket of snow lasts from November until April because of its exposure to the north-west. The area is mainly a big basin where, for centuries, first shepherds and later cowherds have been bringing their beasts to pasture. Green pastures, rich in good grass and wildflowers in summer and no precipices that represent a danger for them made and continue to make the area the ideal place for this activity. The area is now accessible by road.
The mountain peaks are mainly rocky and covered in bushes of dwarf pines, which grow here in large quantities. Reaching the tops you can enjoy an amazing view over Lake Garda (east), the Adamello Group of mountains (north-west) or Valle di Ledro with its lake and crown of mountains around Val Concei (north). It is quite a steep climb but worthwhile, and the walking time is very short considering you can go up by car as far as 1,700 m.
The flora is very particular and botanists from all over Europe come here to study the endemism. The first to recognize the importance of the area, was Caspar von Sternberg (1761-1838) who, during his trip to Trentino, discovered here a variety of Saxifrage, the Saxifraga arachnoidea, and a new Columbine. In the middle of the 19th century two more experts chose Valle di Ledro for their studies: Francesco Facchini (1788-1852) and Friedrich Leybold (1827-1879). The first found a new Scabious (Scabiosa vestina), the very rare Spitzel's Orchid (Orchis spitzelii) and a Daphne but he did not succeed in publishing this last discovery because he died and so Leybold, who arrived here the same year, officially discovered Daphne petraea (Rock Mezereon). He found also Ranunculus bilobus (Bilobate Buttercup) but it was described only five years later by Bertoloni. In 1854 Pietro Porta came here and found a Campion with big purple flowers that others had not found: Elisabeth's Campion (Silene elisabethae).
Other botanists have scoured these mountains looking for other plants and still today there are universities who come regularly to study the nature and the environment of Tremalzo, considered one of the richest gardens, from a botanical point of view, thanks to its concentration of endemisms.
Passo Caset is a strategic point for bird migration. In the past it was an ideal hunting post and today equally well-situated to study the birds' movements.
Bocca Casèt is a pass which, thanks to its funnel shape, is chosen by birds during their migrations from Northern Europe to Southern Europe. The ridge, running in a NNE- SSW direction, marks the watershed between the water basins of the Ampola and Ledro Valleys.
The history of Bocca Casèt as an ideal point to capture a lot of birds began in 1849, under the Hapsburg Empire, when Claudio Ferrari bought the servitude of the territory. Ferrari put up some nets to trap the birds and built a small house from which observe them. The original house has been subsequently enlarged.
The next owner was Sir Agostino Zecchini, the "Boss of the Lake", a very rich and influential person. He and his family continued to hunt birds until it was definitively forbidden by the Empire in 1899. In 1920, with the Kingdom of Italy, hunting birds with nets was made legal once more. The Zecchini Family still owned the servitude but a group of men worked at the pass. In 1929 the nets captured something like 27,000 birds. This gives an idea of the ornithological importance and wealth of Casèt. The following year hunting with nets was forbidden again. In 1943 the Zecchini family sold the servitude to a group of men, who, despite the ban, hunted anyway. They continued until 1955, then this practice was no longer tolerated and the local authority obliged the men to change how they hunted.
Finally, in 1992, a group of bird enthusiasts, aware of the importance of Bocca Casèt for the migration of the birds, built some nets to trap and put a ring on them. In five days they ringed 467 birds of 18 different species. This research continues and since 1996 the Museo Tridentino di Scienze Naturali, now MUSE, has been running this project. From 1996 to 2011, 400.000 birds belonging to 174 different species, have been ringed. The work at Bocca Casèt is included in the Alps Project, a collaboration between the MUSE and the Istituto Nazionale per la Fauna Selvatica (National Institute for Wild Fauna), which started in 1997.
To get to know the story and environment of Tremalzo and bocca Caset, there is a Visitor Centre open during the summer months (free entrance).