How Do Plants Freeze?

How can we prevent it?


††† Star-Tip 1062

Gardening Tips for successful and beautiful Landscapes and Gardens


In a botanical briefing by Professor Roger S. Pearce of the Department of Biological and Nutritional Sciences at the University of Newcastle England, he discusses the various aspects of just how a plant freezes. His article in the Annals of Botany, on this issue; state that Plants and plant parts freeze when they can not avoid nucleation.


One form of Nucleation is the action where the water molecules (inside the plant) come together to form an ice nucleus; much like a little active yeast gets the whole loaf to ferment. This action can take place internal to the leaf or external. A microscopic ice crystal forming on the surface of a leaf can initiate the entire inside of that leaf to completely crystallize and freeze.


This is where we, as caretakers for our plants can help, and how burlap, or even a roof can be so helpful. Ever wonder why the plants out in the open freeze and yet the ones, basically at the same temperature but covered by a roof do not? Or, even better yet; Did you ever wonder how a thin piece of burlap could possibly help a plant keep from freezing? Surely the temperature under the burlap could not be significantly warmer than outside it!† ??


The freezing process often begins with the freezing of a very small droplet of moisture on the surface of the leaf. After this droplet crystallizes it triggers the nucleation process inside the plant. If that droplet is prevented from being deposited on the leaf, this process does not begin. When we cover our frost tender plants, we in effect minimize the access for these droplets to fall onto the leaves and later begin the freezing process.


So, itís not that we are protecting the plant significantly from temperature itself, itís that weíre keeping the surface of its leaves dry, and reducing the opportunity for the internal crystallization process to begin.


There are for certain other factors that play a big role in frost damage to plants; basic plant characteristics as well as the current state of a plants health are also critical to this. We can try to select more cold resilient plants, and we can properly fertilize and water our plants to improve their health. But the real benefit of protecting vulnerable plants from cold damage through the moisture shielding of a protective cover like burlap should not be overlooked.




© 2007, Star Nursery, Inc.††††††††††††††††††††††††††††††††††††††††††††††††††† Copy Provided courtesy of Star Nursery