Landscape and Irrigation is read by decision makers throughout the landscape and irrigation markets — including contractors, landscape architects, professional grounds managers, and irrigation and water mgmt companies and reaches the entire spetrum.
Issue link: http://read.dmtmag.com/i/574585
SPECIAL SECTION 32 October 2015 Landscape and Irrigation www.landscapeirrigation.com BY BRANDON M. GALLAGHER WATSON Many years ago, before I got seriously interested in arboriculture, I was at an event at our local arboretum. It was in the middle of winter and, being in Minnesota, it was quite cold. The event had tables set up for all sorts of local "green" clubs trying to recruit fellow green geeks to join their groups. It included master gardeners, the fanatic rose growers, the begonia society, and so on. The booth that caught my eye was the bonsai club; so I went over to check out the small, twisted trees in pots. One specimen was particularly striking, I can still picture it today; it looked like a perfectly scaled miniature tree with its roots growing over a rock. One problem though, it looked dead. I asked the guy at the booth what kind of tree it was, and he informed me it was a Japanese maple. I said, "It's beautiful, is it dead?" He informed me it was quite alive. When I asked, "Why doesn't it have any leaves then?" He paused for a moment, and being polite to my ignorance, he replied, "Because it's winter." What I didn't understand at the time was even though this tree was "domesticated" and being kept in a pot, it was still going through all the cycles of the seasons. In fact, it had to go through the seasons to stay alive. Many bonsai trees have been killed by loving owners who think they are helping their living sculpture by bringing them indoors when the weather changes in the fall. This is the same reason why the species we consider houseplants are all from tropical regions where it is 72 degrees Fahrenheit year- round, while you could not keep, say, a hosta in your living room for more than a year before it would die. Plants that are adapted to temperate climes must go through a cold rest period, known as vernalization, in order to complete an annual cycle. As the trees in our urban forests prepare for cold, they go through several physiological changes. The most obvious is probably the turning of fall leaves on deciduous trees. The leaves have actually been preparing for their annual leaf drop since they budded out in the spring. Glucose has been moving out of the leaves to feed the tree, and waste products have been moving it. Along the base of the petiole, where the leaf attaches to the twig, is a line of cells known as the abscission layer. While actively growing, there are a series of tubes running through the abscission layer transporting water from the vascular system into the leaf. When triggered by a decreasing photoperiod, the cells in this layer swell and form a cork-like material, known as suberin. As the suberin swells and expands, the abscission layer begins to prevent water from entering the leaf. Glucose, pigments, and waste products remaining in the How Trees Get Ready For Winter Colorful pigments are revealed as chlorophyll products ceases. PHOTO COURTESY OF RAINBOW TREECARE SCIENTIFIC ADVANCEMENTS