The coldest place in the world is probably the Arctic Circle. There are places where it gets -50°C (-58°F). But there are no places colder than -40°C (-30°F), which is known as “zero degree”. That’s because zero degrees does not exist anywhere else in our universe. Zero degrees is just the temperature at which all physical processes cease to occur.
Nothing exists but massless energy, and nothing can move except through empty space.
In the northern hemisphere, zero degrees occurs when one reaches the North Pole. To reach that point requires traveling across land masses of ice and snow, mountains, glaciers and ocean water. One must travel along rivers and seas as well as over frozen tundra or mountain ranges. The coldest temperatures ever recorded were found in Antarctica. There, the average annual air temperature was minus 90°F (minus 68°C).
Zero degrees is also known as the freezing point of water. Water freezes at 0°C, so if you could freeze water at any other temperature, your drink would become icy cold!
So what does all this have to do with apples?
Actually, quite a bit. The colder it gets, the slower apples ripen. It’s not easy to grow apples in extremely cold places. Since you can’t alter Mother Nature, you have to alter the way you grow apple trees. In fact, some people have made their entire living growing apple trees for northern areas.
The first thing you must do is plant the tree in the proper type of soil. You don’t need rich loamy soil for an apple tree to grow. In fact, you don’t need soil at all! You can grow apple trees hydroponically. In this system, the tree is grown in water mixed with nutrients.
The roots of the tree do not actually touch the water. They are held up in a system of nets and wires which holds them in the air. This way, the tree gets all the nutrients it needs without having to waste energy growing roots in soil. When you grow apple trees hydroponically, the tree grows faster and produces more fruit than trees grown in soil!
You also feed the tree different types of fertilizer to produce a healthier, heartier plant. To accommodate for the extreme cold, you use two types of fertilizer: Calciferous (to make the plant stronger) and vitascene (to make the plant immune to the cold).
The next step in growing apple trees in a cold climate is to protect it from the cold. This is done by building a shelter around the tree and heating the shelter. There are two main types of shelters: the glass-in type and the poly-tunnel type. In a glass-in heated shelter, professional horticulturists build a wooden or metal frame around the tree. Then they place sheets of glass against the frame.
The inner side of the glass faces the tree and is coated with a transparent insulator to keep the heat in. The heating unit is installed outside the shelter. This type of shelter works well, but if there is a power failure, your trees will freeze!
In a poly-tunnel, flexible sheets of plastic (polythene) are installed against a wooden or metal frame. The sheets are installed with the inside against the frame, and the outside of the sheet faces the tree. Unlike the glass-in shelter, the heating unit is installed inside the shelter near the tree. This keeps the heat in better and protects it from the elements (wind, rain, snow). If there is a power failure, however, the heat can escape as easily as it came in.
Sources & references used in this article:
Low chill Apple cultivars for north and north central Florida by PC Andersen, TE Crocker – 2000 – Citeseer
Influence of spraying with gibberellic acid on behavior of Anna Apple trees by EAM Mostafa, MMS Saleh – J. Appl. Sci. Res, 2006 – researchgate.net
Induction of budbreak in apple trees that received insufficient chilling by hydrogen cyanamide by S Subhadrabandhu – … on Growing Temperate Zone Fruits in the Tropics …, 1993 – actahort.org
Transpiration of apple trees in a humid climate using heat pulse sap flow gauges calibrated with whole-canopy gas exchange chambers by D Dragoni, AN Lakso, RM Piccioni – Agricultural and Forest Meteorology, 2005 – Elsevier
Bud dormancy in apple trees after thermal fluctuations by R Anzanello, FB Fialho, HP Santos… – Pesquisa …, 2014 – SciELO Brasil