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www.arborage.com ARBOR AGE FALL 2015 9 PLANT HEALTH CARE Evergreens prepare for the change in seasons in other ways. Conifers have leaves already modified to resist drought and freezing temperatures in the form of needles; but that doesn't mean they don't shed their foliage in the fall like a deciduous tree does. Conifers will drop leaves every fall, just not all of them. Typically, conifers retain 3 to 5 years worth of needles, meaning every fall they will shed a layer of older needles. I used to work at a garden center where every fall we were bombarded with "My pine tree is dying!" phone calls. We would ask if the tree was dropping needles from the tips of the branch or from the inside of the tree. 100 percent of the time it was from the inside. After ensuring them this was perfectly normal, we would take the time to inform them their pine was actually a spruce. Of course, there are exceptions to the rule, such as the larch or the dawn redwood, which will drop all their needles each fall. Needles that are retained generally do not freeze in the winter, even in extreme temps, as their resin acts as a natural antifreeze. Beyond the foliage, trees are prepping for the cold in other ways. Temps can drop pretty low in the winter (often to -20 waste products remaining in the leaf become trapped there, and, without a water source, the green color begins to fade. So what about the vibrant fall colors? During the growing season, leaves are actively taking in CO 2 and using sunlight to combine it with water to make sugar and oxygen through photosynthesis. This makes chlorophyll, and chlorophyll, of course, gives leaves their green pigment. As fall approaches, and the days get shorter, the leaves cease producing chlorophyll and the green color fades. The bright colors that are revealed were actually there all season long but we couldn't see them as the chlorophyll was blocking them. The yellow-orange colors result from carotenoids, the same pigments that color carrots, bananas, and daffodils. The reds and purples are caused by anthocyanins, the same molecules that give apples, plums, and grapes their iconic hues. The browns revealed in trees such as beech and oak are tannins, the bitter-tasting waste product that is left in the leaves (that also gives tea its color). All leaves have stored waste products, but the coloration is often blocked by other compounds so we don't see them until the leaf as completely died — hence why all leaves will eventually turn brown. Snow acts as a insulator, keeping the soil warmer than the air. PHOTOS COURTESY OF WIKI COMMONS Even trees "in captivity" go through a dormant cycle.