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September 23, 2004 Fall Needle Drop in Conifers During autumn, deciduous trees like green ash and linden change color and lose their leaves. This is normal and expected. It happens every year and people are used to it. “When evergreen needles turn brown and die, it’s definitely unexpected, but not necessarily abnormal,” according to Joe Zeleznik, North Dakota State University Extension Service forester. There are several species of evergreens or conifers that are grown in North Dakota. Pines and spruces are most common. Pines have relatively long needles (two to nine inches), which are held in clusters called fascicles. Scotch pine trees have two needles per fascicle, about two to four inches long, that are usually twisted around each other. Ponderosa pine needles are in bundles of two or three (usually three) and are four to nine inches long. These needles live for two to seven years and then die and drop during the fall. These are the older needles toward the center of the tree. “The needles that are going to drop start turning yellow as early as late August,” Zeleznik says. “By mid September these needles turn brown and begin falling from the tree.” Another common group of conifers are the spruces such as Colorado blue and Black Hills. These trees have shorter needles, about three-quarter to an inch long, and are attached to the stem individually, not in bundles. Blue spruce needles are more pointy or sharper, than those of Black Hills spruce. Spruce needles usually live longer than pine needles and may persist for up to 10 years. Just like pines, the spruce needles, which are older and more shaded, will turn color and drop during autumn. Some needle drop by conifers during the fall is normal. “The exception to this rule occurs with larch trees (also called tamarack),” Zeleznik says. “Larch trees lose all of their needles every year because they are deciduous evergreens. Larch needles are one to two inches long and borne in clusters on short shoots or individually on long shoots. The needles are also very soft. Some larch trees are native to the swamps and bogs of northern Minnesota. A common larch that has been widely planted in North Dakota is the Siberian larch. Larch needles turn bright yellow and provide a golden rain during autumn.” Evergreen needles don’t last forever. Some needle loss toward the center of the tree during autumn is normal. Needle loss at other times of the year is not normal and may be due to an insect or fungal pest or the result of severe environmental stress. Larch trees, the exception to the rule, lose all of their needles every year. Enjoy the colors this fall. ### Source:
Joe Zeleznik, (701) 231-8143, joseph.zeleznik@ndsu.nodak.edu |
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