Frosty

Well cold and frosty here today. Why dont plants like frost...I've never really understood the scientific reasons....it breaks up the soil doesnt it? so surely thats good for aeration, is it something to do with inhibiting the roots water supply???

 

Depends on the origin of the plant, B.
If it's from a part of the world where the emps don't go that low, then it's not likely to cope with it. But mostly it's not so much the frost itself if the plant is in the soil - as the soil will protect it to a degree, it's more of a prob if the plant is in a container, where the roots can be frozen solid.

As for the science behind it - think of it this way - we wouldn't be able to function if the liquid in our veins was frozen solid...... :D

 

Its alot to do with the repeated freezing and thawing. Also wet/cold plants being burn't by warm morning sun. Things like bananas which are full of water go squishy after repeated freezing and thawing. I read also that it's similar to frozen water rupturing a pipe. As the sap in the cell freezes, its volume increases and damages the cell walls.

 

Some plants can be killed by internal dessication by frost. If they have leaves then they continue to transpire moisture into the cold air. Normally moisture would move up the plant through the cell walls and in from the roots. Moisture is then pulled through the walls of the roots by this process. If the soil water is frozen then this process cannot take place so the plant dehydrates. Plants of the colder regions get round this in various ways. Many become deciduous in winter so that stops the transpiration. Evergreens from cold regions often have waxy coatings to their leaves and this cuts down transpiration loss. An example of this was one winter about 20 odd years ago. We had a long spell of very cold weather and the ground was frozen for weeks. At my allotment site it was so cold all the wood pigeons were dropping dead. On one side of the allotment there was a 300 foot Leylandii hedge, 8 feet high. Now Leylandii originates from the mild Mediteranean region and does not have hard waxy leaves. It was killed stone dead.
I also noticed in the area that there were a lot of high laurel hedges and these lost all their top growth but did shoot again from the base.
Some plants may also have cells that expand with the freezing and then rupture, destroying the cell structure. I think this may happen with dahlias that get frosted. I think it may also surprisingly happen with primula denticulata (drumstick primula)that are in pots. They have thick fleshy roots and on occasion I have found them turned to mush after prolonged frost.

 

OK, so I over-simplified..... :rolleyes: but my post is easier to follow! :D

 

Thanks Geoff- spot on.

 

Geoff is absolutely right. In his last paragraph he talks about cold destroying the cell walls. This is exactly the same as in a car. Freezing water expands and can burst your engine block, in the same way as it bursts water pipes in the house. The answer with a car is to use antifreeze, which lowers the temperature at which water freezes. Differant plants contain different levels of natural antifreeze.