Too much of anything is bad -- even when it comes to watering your trees. Roots need oxygen to survive, but overwatering your pine tree will drown it. Air pockets in the soil fill with moisture, and the roots are unable to "breathe," leading to death of the tree, if the problem is not corrected quickly. Unfortunately, symptoms of overwatering often resemble those of insufficient watering, which can lead well-intentioned gardeners to the application of yet more water. However, there are some telltale signs that will distinguish between drought and drowning.
Walk across ground at your pine tree's roots. Watch the soil as you walk. Notice if water wells out of the soil or if your feet sink in. This procedure gives you a quick feel for conditions in which the tree roots may drown. While water may well up easily immediately following a deep watering, the ground itself should not feel spongy. Moreover, constant sponginess of the ground and excessive welling of water with pressure is a sign of continual overwatering.
Reach down and scoop up a handful of soil. Notice if the soil feels particularly wet -- not just moist -- and if it smells like sewer or rot. Close your fist around the dirt and release, to determine if the soil will hold a ball or crumble apart. Soil that stays balled up, feels muddy, or drips water, indicates overwatering. If the soil smells like sewage, it has been overwatered often, and your pine may be in imminent trouble.
Poke a broomstick handle or a similar rod straight down into the soil, to test the soil resistance. Your probe will penetrate moist soil easily, but when it encounters dry soil, it will stop or prove difficult to push. Your subsurface soil moisture should extend to about 18 to 20 inches in depth. If you do not encounter resistance at this depth, the soil around your pine tree roots is too moist, indicating overwatering.
Look at the needles on your pine tree. Needles that droop or wilt or appear discolored may indicate overwatering. Your pine tree may begin to lose branches as the needles turn brown, first toward the bottom of the tree, then working upward. Feel the needles to see if they feel brittle and abnormal.
Examine the pine tree's bark to find evidence of cankers, caused by fungus growth due to root rot. Cankers -- areas of diseased tree tissue -- may appear as discolored lesions on your pine's trunk or cause yellowish oozing through the tree bark. Whenever the tree's roots are stressed, the evidence is bound to appear in the tree, but often only after extensive damage is done. So if you notice any of these signs, it may already be too late to save your pine tree.
Search for evidence of algae or mushrooms growing nearby. Fungi such as mushrooms require very damp conditions, which indicates that the soil is, and remains, too moist.