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Why you decide you ask this treemendous kweschun? Perchance you are ever green with envy of those who are in the know but leaf it to others to ask before imparting their wisdom, for fear that the knowledge will be sapped from them. One of the root causes of botanists going barking mad or branching out into some other discipline. Alright, so that was a corny thing to say. But I have given you previous warning, Mr Sheepy.Sow So, what are the advantages of being evergreen? Well, for starters growing leaves is a pretty costly affair, so if you can hang on to them through the winter, you’ll be in a fine position to start photosynthesising as soon as spring comes around, ‘cause you’ll already have your leaves. What’s more, you can get on with growing straight away, rather than having to grow a whole new canopy first. But leaves in winter present some serious problems. They can freeze and act as giant sail, catching the wind and putting the tree at risk of being blown down. So the evergreens of the cooler temperate zones tend to have rather small cylindrical leaves. These do have some distinct advantage for those evergreen trees. They require less food (most of these trees are native to regions where the soil is poor), are resistant to very low temperatures and help to conserve water.The deciduous trees have to grow a whole new canopy every spring. That requires a great deal of energy, but these trees do tend to live in far better soil. In fact, their own leaves, once fallen, help to enrich the soil. Their large leaves would become severely damaged by sub-zero temperatures, but large leaves capture more solar energy so they photosynthesise at a far greater rate than the needle like leaves of the evergreens. Discarding your leaves for the winter minimises the risk from damage by high winds and sub-zero temperates.But evergreens are not restricted to the temperate zones. Many trees in the equatorial regions are considered to be evergreens. As they are not liable to experience the freezing temperatures that the temperate evergreens have to put up with, they can grow large leaves, just as the deciduous trees do. The difference here is that these trees do in fact shed their leaves, but not all at the same time. Where the deciduous trees shed all their leaves during the winter, these tropical trees will loose more of their leaf during the high summer. This is to reduce water loss through the leaves at a time of high temperatures, blistering sun and lower rain fall. But it is these trees which have the best of both worlds. Remaining evergreen throughout the year, they can photosynthesise continuously, where the trees, evergreen and deciduous, of the temperate zones must close down during the winter months. This continuous growth, enabled by rich soil, the forests’ own ability to produce good rainfall and year-round sun, has led to the largest living organisms on Earth.A Sequoia being one of the largest organsims on Earth early today.Pretty clever things these leaves and I have really only scratched the surface of their complexity. I think we should all hug a tree. If the order was given, I would, wood yew?
And, too, as well, forby, just because they have needles and cones, they may not be "evergreen". The forests around here are mostly fir and pine, but there is a lot of larch mixed in. In the summer, the larches look pretty much like a fir tree, but they turn yellow in the fall and dump their needles.The following link will fill you in on any minor details I may have overlooked.http://www.mountainlarch.com/Mountain_Larch/Home.html
So could there be a half way house between Evergreen and deciduous ?
Well, I dunno, but that seemed like a professorial response to me. Are yew sure you are not actually a prof of biology at some uni?
But leaves in winter present some serious problems. They can freeze and act as giant sail, catching the wind and putting the tree at risk of being blown down.
The hardwoods tend to have multiple upward branches, essentially forming a ball shape. They would be seriously at risk of collapse if they had a severe snowstorm with a full canopy of leaves.
Evergreens will usually do much better in an ice storm, but only if they have symmetrical foliage. If they are crowded, the foliage can be very asymmetrical, so the weight of the ice starts to bend the trunk. Once that happens the buildup of ice accelerates, and it's just a matter of time until the trunk snaps. It's amazing just how much they will bend before they snap.