As we bundle up and head outside during February we often confront the coldest temperatures of the year. Standing water is frozen solid, snow falls, and wind chills can approach zero degrees. It is hard to imagine how plants can possibly survive in weather this cold, especially when we consider the fact that water can make up 90% of the weight of plants. Thankfully plants have a natural anti-freeze that helps to prevent the water inside from freezing. Plants store the sugar they make during photosynthesis in cells throughout their roots, stems, and leaves (if they still have leaves). In addition, they store minerals they uptake from the soil. Plants also produce a range of natural oils that thicken their sap. The sugar, minerals, and oils mix with the water to create a natural anti-freeze throughout the plant. This mixture will not freeze at 32 degrees. In fact, depending on the individual plant – the mixture can be so effective that it may only freeze at temperatures of 40 degrees below zero or colder.
The one thing that plants cannot tolerate is to have ice form inside their cells. Water expands as it freezes and the resulting expansion can stretch and then break the cell wall – the resulting damage can be catastrophic. If enough cells die – the plant dies as well. Some plants have a remarkable method of combating this. In late fall they move much of the water outside of their cells – into the area in between cells. If water freezes between cells it is much less likely to puncture the cell wall, than if it were within a cell. When spring arrives the water moves back into the cells.
Roots can be some of the most vulnerable parts of a plant when it comes to cold hardiness. Thankfully the soil is a relatively good insulator. Although the soil in our area typically freezes to a depth of 12 or more inches every winter – the antifreeze quality of sugars, minerals and oils helps protect the roots. Interestingly a good blanket of snow is a great soil insulator. The air space between snow crystals is a natural insulator and a blanket of snow can stabilize the temperature of the soil below. A layer of snow can affect soil temperature by as much as 10 to 15 degrees.
Hopefully this helps you understand how nature protects those plants that have given you so much pleasure during the spring, summer and winter seasons. These unseen processes ensure that those plants that are perennial in nature are thriving once the temperatures rise. Spring is close by and your plant favorites are doing fine during winter’s harshest weather.
