Leave them in the cold
Always those who produce plants or design gardens have tried to bring special plants to our green spaces, with unusual flowering periods, decorative foliage, and intense colored buds. Most of these plants come from tropical areas or distant countries, such as South Africa or Australia. In general, these plants are grown in the nursery for a few years before being put on the market, to understand what their behavior is with the European climate; a good part of these plants can easily find a place in the garden, without the need for special protection, while others prefer the cold greenhouse.
Places of origin
Some of the very decorative plants that are present in our gardens or even in the apartment come from places where the climate does not differ much from ours, or a hot and dry season follows a wet and cold season, followed by a very cold season but dry and therefore temperate and moist. The only exception is due to the fact that in many areas the winter season is very dry, while in Europe, if the temperatures do not drop much, the winter climate is quite humid. For this reason it is sometimes sufficient to prevent our plants of exotic origins from spending the cold season in a dry place, for example sheltered by a layer of plastic film, which does not allow precipitation to add the soil.
Among the particular plants most widespread in the garden we certainly find a large Australian delegation; starting from mimosas and eucalyptuses, grown for years in Italy, we can find many other ornamental plants, such as grevillee, callistemon, leptospermum. These plants come from Australian areas where the winter lows are some degrees below zero, while in summer the climate is decidedly hot. Therefore most of the varieties of these plants that are widespread in the market can be grown in the garden in most of the peninsula, without having to worry about the climate; in some cases it is however good, especially in the northern areas, to cover the crown of the shrubs during the coldest days, when the thermometer drops many degrees below zero.
Other plants that are widely cultivated in Italy instead come from Asia, such as ardisia, or some species of polygala; these plants can remain in the garden throughout the year, they only fear very intense or very long frosts. The Ardisia crenata was once cultivated exclusively as a houseplant, while it can easily withstand decidedly harsh temperatures, many degrees below zero.
Some very common essences come from Africa, a typical example is geraniums; these are shrubs that do not fear some degrees below zero, but are damaged by very intense frosts; and above all during the winter they go into vegetative rest, and do not need water; therefore in most of the peninsula they can find a place in the garden, as long as they are in a very sunny place and protected from precipitation; in the rest of the peninsula it is advisable to repair them with non-woven fabric or plastic film.
A good part of the succulents of South American origin, the cacti, tend not to fear the cold, and can withstand even decidedly lower temperatures; indeed, most of the cactaceae show much more abundant blooms if they spend the winter in a cold place; the same applies to agaves, aloes, crassulas.
Surely in the colder areas of Italy it is the case to repair the succulents, avoiding however to place them in a heated place; placing them in a cold greenhouse these plants follow the correct natural course of the seasons, similar to the one they would undergo in their places of origin; instead cultivated perennially in warm climate the plants tend to have a scarce development, with often absent blooms. The only problem that can occur in succulents is due to water: during the winter vegetative rest period they must be kept in a dry place, therefore away from precipitation.
Cold plants: Indoor plants
Much of the houseplants in nature develop in damp places, with temperatures ranging from a maximum of 25-35 ° C, up to a minimum winter of 12-15 ° C. So we can cultivate the ficus or the schefflera also in a stairwell (obviously away from blows of air) remembering to increase humidity during the summer months by vaporizing the foliage. If instead we grow our plants at home, we avoid placing them in contact with heat sources, such as radiators, fireplaces or away from underfloor heating; and periodically increase the environmental humidity by vaporizing demineralized water.
Some houseplants, such as the Ardisia that we talked about earlier, or like the dragon trees, can also withstand very cold temperatures, close to -8 / -10 ° C, so if we want we can leave them on the terrace, even during the most intense frosts of the year.