Four winds influence the shape of Venetian gardens

Know your winds in Venice: Winds brushing over the lagoon influence how gardens in Venice look like. Venetian gardeners use sipari (trees planted in rows) to protect monastery gardens, and pergolas to shield private gardens from the sometimes hefty winds that reach Venice unhampered from all four directions. Here you can read how and when Venetians use sipari and pergolas and take a look at examples; a monastery garden, a public garden, a 15th century palace garden used as restaurant - and finally, a secret and secluded garden.
With winds that occasionally batter the lagoon as there is no protection against the sea towards the south, the soil in the lagoon might easily erode. So plants are used to form barriers to provide shade and solid ground. Therefore, sipari (tree-lined pathways) and pergole are typical because essential elements in Venetian gardens, used in particular in vegetable gardens and mixed gardens. There is more to the pergolas than just being used for decorating gardens. 
Sipario on the island of San Francesco del Deserto: this island with its famous monastery is completely exposed to winds in the lagoon, so the cypress trees provide shade and shelter 
Knowing your winds in Venice is important to structure "garden rooms" in a prescient manner. Sheltered gardens contribute to the survival and well-being of plant species in the lagoon, so Venetian gardeners need to select the right plants and the right garden shapes carefully to make gardens last in this special environment. 
Gardens in the midst of the lagoon, exposed to the winds from all directions
Basically, there are four kinds of winds: the southern wind, scirocco, churning up the waves towards the northern rim of the Adratic sea, pressing water into the lagoon. Now you can imagine that this wind, combined with rising tides, brings on acqua alta. Scirocco also shuffles humid air into the lagoon, soft and moist but also hot and stifling in many summer evenings. Northern winds are rather hefty, these winds are called bora. You can cannot mistake their effects in winter, the bora makes your cheeks turn red and burn. The libeccio (south-westerly wind) and levante (south-easterly wind) are felt to a lesser extent. 
A sheltered spot in the garden ...
What I call "sipari" (literally: curtains) were used to protect the first gardens in the lagoons, set up by the monk gardeners of the first monasteries on the lagoon islands around the 6th and 7th centuries AD. The sipari divided their vegetable gardens into rectangular fields en miniature, with vegetable plots being separated by narrow sentieri (pathways), that were sometimes paved and sometimes covered with gravel or just makeshift and narrow. 
Imagine what this garden would look like without shelter - even olive trees thrive here on San Francesco del Deserto, their silver leaves add a special hue to the verdant environment
In private and palace gardens in Venice, on the other hand, pergolas are used to protect protect plants, humans and animals from the sometimes oppressing summer heat and parching wind.
A taste of a Venetian pergola accessible for all in a publc garden located next to San Marco: Pergola di glicine at the Giardini Reali. Imagine what they will look like when they are in full bloom in April !!
And which plant is used most often to set up pergolas in Venice? Undoubtedly, the vine. The Venetian lagoon is not new to vineyards: Some 100 years ago, the monasteries in the lagoon used to produce their own wine, and the vineyards of the Serenissima Republic of Venice located on the lagoon islands had also been well-known. The Venetian initiative Laguna nel bicchiere was formed to recover this particular heritage to the lagoon.
The Redentore gardens (mixed gardens) from above: structured by sipari (hedges, rows of trees). Actually, here you can also see the garden I dubbed as "secret" just north of Rio della Croce. Quite a large extension, can be viewed only like this, from above.
Vines grow fast and are thus able to provide shelter to other plants growing below, and also to birds and other animals. In the ancient gardens of Venetian noble families, the pergola used to be a defining element and favorite spot.
Fast and lush growing vines are used most often for pergolas in Venice
Even though roses could be used for pergolas as well, and sometimes are of course, I find that mostly vines are used for pergolas in Venetian gardens. And sometimes wisteria is chosen for pergolas - which really looks great in April with their purple and fragrant flower cascades.
Vines forming a roof over the garden and separating one "garden room" from another

If you would like to see a garden "decked out" with vines used as pergola, this is possible right in the center of Venice, in the Sestiere di Castello. Last September I wrote a post on the restaurant Al Giardinetto which is located in a 15th century palace garden. From Easter time, that is late March, you can enjoy sitting in a  garden in Venice without being cold. At the restaurant Al Giardinetto, you can get to know the uva fragola vine variant, which by late August regales us dark blue grapes. 
Grapes waiting to be picked

Garden rooms separated by vine pergola, and a row of pot plants (begonias)
And finally, it is the turn of the secluded garden's pergola to be presented, a garden that is still off-limits to the public: Giardino Eden. Here I took a picture from the book written by its former British owner, Frederik Eden, where you can see an ancient vine pergola protecting lilies and other plants from the unrelenting Mediterranean sun. By the way, you can read more about this particular garden in one of my entry pages dedicated to this special garden.
The vine pergola of garden Eden - the one really secret garden in Venice