The drip line of a tree is the imaginary line on the ground at the furthest edge of a tree's canopy. You can see the dry mulch in the image below where rain has been blocked by the canopy, making the drip line perfectly visible.
What does "drip line" mean? During a rainstorm, trees catch precipitation and funnel it to the tip of each leaf. As moisture falls to lower leaves, it continues to move out until it reaches the edge of the canopy where it then falls to the ground. This is the "line" in which the moisture "drips" from the tree. The small, fibrous, feeder roots are located at the drip line where they can absorb moisture and other nutrients and send them to the rest of the tree. The roots between the drip line and the trunk have less to do with intake and more to do with anchoring and stabilization.
Water Dripping From Leaves
Fertilizing and watering of fruit trees should be done near the drip line instead of next to the trunk. When building a berm of soil around your tree to capture and hold water, make sure that it extends to the drip line. Also, fill the dish with a layer of organic mulch to help retain water and to minimize the growth of competing weeds that will rob the tree of moisture and nutrients.
Trees located in lawn areas should, ideally, be free of grass from the trunk out to the drip line.
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