Question
Is it true that a pine tree's tap root is about as long as the tree is tall?
Thank you
Melanie


Answer
It will depend on the species of pine and the soil type it is growing in. If the water table is deep the tree will send deeper roots down but in shallow water table soils the tap roots is shallow.

As a longleaf pine tree continues to mature, both the lateral and tap roots continue to grow. In mature trees, roots radiate out laterally an average of 35 feet from the trunk (some roots may travel up to 75 ft). Longleaf differs from other pines in that the tap root is nearly as large in diameter as the tree's trunk, tapering gradually to depths (on average) of 10 to 15 feet.

Tree root systems have three purposes: to collect nutrients, to collect water and to support the tree and keep it from tipping over, explained Dr. Laurence, who is also an adjunct professor of plant pathology at Cornell. Trees produce several different kinds of roots, he said.

The feeder roots, which explore the soil for nutrients and surface water, grow close to the surface and spread out from the trunk, Dr. Laurence said. Another kind, called coarse roots or water roots, grow both down and out, he said, trying to tap into a reliable source of water. The upper layers of soil generally provide the most nutrients but also dry out the fastest so the coarse roots look beyond and below the trunk area, he explained. Some trees have a taproot that is sent straight down for water and also provides support.

The overall root pattern, including whether there is a taproot, can be determined by considering the tree's species and the underlying soil structure where the tree is growing, Dr. Laurence said. If there is hardpan (hardened soil) or bedrock below, the tree does not bother with a taproot.

The loblolly pine, for example, has a big taproot because it tends to grow in areas where the soil is deep and loosely packed. The spruce, on the other hand, tends to grow in thin soil and does not bother with a taproot.