|MadSci Network: Botany|
Your question is a good one. In winter, many trees lose their leaves and the shoots of many shrubs die back to the ground. This does not mean that the plants are dead, just that they are dormant. When a plant is dormant all its life processes are going on but at a very slow rate. When spring comes, little buds in the tree and the shrub reawaken and give rise to brand new, green leaves and shoots. So, I think that if if you were to look very carefully at the plants in question, you will probably observe that the old brown parts arenít turning green, but that they are being replaced by new green parts.
Biologists are very busy trying to figure out why some plants can survive in cold weather and other plants canít. I bet thereís not too may banana trees in Deerfield! Perhaps if we can understand why banana trees don't like cold weather, we might be able to change them so that that they could grow in Deerfield! We don't have all the answers, but one thing seems certain. Plants that are preparing for winter store lots and lots of sugars and salts. Now, youíve probably seen people adding salt to their sidewalks during winter. They do this because salty and sugary liquids have a lower freezing point than does pure water. (You can test this at home by adding sugary water to half an icecube tray and pure tapwater to the other half, and seeing which one freezes first!). So, by storing lots and lots of sugars, the plants are more resistant to ice formation, and this helps them survive through winter.
Try the links in the MadSci Library for more information on Botany.