A characteristic feature of our climate is the periodic occurrence of severe winters, during which the temperature drops below -30 ° C. Winters like this are repeated in our country 11 years, although there are and more often. The winters in the years that were so painful for the horticulture in the current century 1928/29, 1939/40, and recently, called "the winter of the century” in year 1978/79. Strong frosts occur throughout Poland, but the largest and most common are found in the mountainous regions and in the eastern parts of the country. In many cases, they exceed the strength of some species and varieties of fruit trees and shrubs, causing them to freeze. The north-eastern areas are also the coldest districts in our country (voiv. Olsztyn, Białystok, Suwałki), eastern (Lublin, Chelmskie, bialsko-podlaskie) and Southeast (Przemyśl, Rzeszów, Zamosc). This should be borne in mind when planning the planting of fruit plants and some ornamental plants that are not resistant to frost.
In our climatic conditions, spring frosts usually end around mid-May, the autumn ones begin at the beginning of October. However, due to the high variability of our climate, frosts often also occur in the second half of May, and even at the beginning of June, causing severe damage during flowering of trees and fruit setting. They also cause serious damage to thermophilic vegetable crops (tomato, cucumber, peppers, beans). This should be taken into account and adequately protected against it (which will be discussed later).
Depending on the heat requirements, vegetable plants are divided into three groups:
1) with low thermal requirements, so resistant to cold and frost, on the other hand, it does not tolerate high temperatures well (above 20-25 ° C); this group belongs to: pea, cauliflower, cabbage, radish and radish, for, lettuce, spinach; they grow best at 10-18 ° C;
2) with moderate thermal requirements; this group includes: onions, celery, Chinese cabbage, broccoli;
3) with high thermal requirements (the so-called. thermophilic), so sensitive to cold (below 5 ° C) and hating frosts; the optimal temperature for their growth is 16-23 ° C; this group includes: beans, tomato, paprika, cucumber, pumpkin, melon, eggplant.
Another climatic factor, decisive in the cultivation of horticultural plants, there is precipitation, which, however, are of less importance in amateur cultivation on plots or in home gardens, because we have water intakes here, that allow you to water your crops as needed. On the other hand, hail may play a special role, which can cause severe losses in gardens. Heavy hail (when the ice blocks are large) can destroy foliage completely, flowers and fruit buds, and even young shoots of fruit trees and shrubs, and completely cultivating vegetables or ornamental plants. In some places, hailstorms repeat almost every year. 0 we are talking about these areas, that they lie on the so-called. hail trails. In such neighborhoods, due to the high risk, the fruit plantings and the vegetable and ornamental plant cultivation plan should be adjusted accordingly.
The distribution of atmospheric precipitation in Poland is uneven, which is the result of the geographic location and topography. Most heavy rainfall (above 1100 mm per year) fall in mountain areas, plentiful (800-1000 mm) they have the foothills of the Carpathians and Sudetes, as well as coastal areas and the Masurian Lake District (600-700 mm). The central areas of Poland are the poorest in rainfall, especially Kujawy (500 mm and less). The annual average for the whole of Poland is 550 mm of rainfall and for fruit plants it is basically sufficient, of course, if their distribution in particular months is appropriate. As for vegetable crops, their water demand ranges from 380 do 780 mm, depending on the species of vegetable; e.g. the onion demand is over 300 mm, while the tomato 500 mm. It is accepted, that plants consume only approx 55% rainwater, therefore, it is imperative to provide an additional source of water when growing them [12].
Insolation is an important climatic factor in the cultivation of horticultural plants. It has a direct impact on the heat of the station and the intensity of assimilation. Only in good sunlight are plants able to produce the maximum amount of organic compounds, which in turn causes their strong growth and abundant fruiting. Insolation also has a positive effect on the development of the fruit, their coloration, taste and durability.
For proper growth and development, plants need sufficiently strong light for a certain number of hours a day. For example, vegetables are generally light-loving plants, but they have different shading sensitivity: tomatoes and cucumbers are very sensitive, onion, cabbage and red beets – less, and rhubarb, sorrel and spinach – least. Often used on plots or in home gardens, growing vegetables under trees reduces the absorption of carbon dioxide and reduces plant growth, and even makes it impossible to produce a crop (e.g. the shaded radish does not form edible lumps). The sensitivity of vegetable and ornamental plants to light deficiency is particularly high just after emergence, what should be borne in mind when producing seedlings.