The Root Cause Of Our Deep South Texas Native Trees Surviving And Thriving
by K.C. Fletcher
published May 2018
The mostly hidden roots of our Mid-delta
Woodlands reveal adaptations over eons of natural
selection to resist local pests and diseases,
to live their life, while buried in the alkaline oftentimes
salty soil, baked by the sun above and
exposed to constant hot dry winds, combining
to cook these special trees along with their upland
Specialized South Texas tree roots will survive to sustain the above ground tree even though those stressed, submerged roots are temporarily deprived of oxygen. Too much soggy soil for an extended period of time will eventually drown our native Texas trees because oxygen diffuses into the water-logged soil 10,000 times slower. Rare occassions of a rapid drop in temperature and a prolonged freeze can also kill our Pharr Honey Mesquites (Prosopis glandulosa).
Tree roots are responsible for the uptake and delivery of the 15 mineral derived essential elements mined from the surrounding soil, including nitrogen gas from the atmosphere, which is converted to root absorbable nitrogen compounds by very special nitrogen-fixing bacteria that live on and in the roots. The mesquite acts as its own fertilizer factory and also allows absorbable nitrogen to build up in the soil. South Texas soil fungus attach to the mesquite's absorbing root to feed off of the absorbing root's sugars supplied by the leaves enhancing the uptake of water increasing the chance of survival for both biological buddies.
The leaf is the food factory for the entire tree as carbon is combined with hydrogen to make sugars that are transported throughout the tree to supply energy for tree growth and maintenance or stored as starch in the roots and elsewhere within the tree. The chemical energy trapped in the leaf-derived sugar compounds is released by recombining with oxygen, which is the definition of respiration. All tree roots need to breathe oxygen in order to power growth and maintenance biochemical reactions.
All 28 species of deep South Texas, Tejanotough, native trees rely on their woody roots, to provide partial support and stabilization to the trunk above ground and firm anchorage into and onto the soil beneath.
The Mesquite tree wears the championship crown for the deepest tap root growing to a depth of 174 feet 10.4 inches straight down. A Texas Honey Mesquite's highest leaves reach an average height of 30 feet, up to 60 feet if that lucky taller tree taps directly into a permanent subterranean water supply. Thusly, the tap-rooted mesquite can extend below ground around 3.25 times the tree's height. This accurately measured fact is not just another traditional Texas tall-tale. The mesquite coneshaped tap root oftentimes grows to a larger diameter than the above-ground trunk. Think of that deep ground water traveling the total possible 230 feet up through the roots, trunk, branches and stems in order to quench the constantly thirsty leaves, high above, manufacturing the sugars and other nutritionally needed compounds for those very roots, the rest of that tree, for wildlife and ultimately, even for the life of you and me.
Lateral roots growing outward on all sides can extend radially 5-6 times the diameter of the branches and leaves of the 30-60 foot wide tree canopy and, especially the thicker primary and secondary laterals in the mesquite, can be bark-covered making it more like an underground canopy, minus the leaves.
The mesquite's lateral roots radiate from the root collar of the trunk with sinker roots growing vertically from them. All act in concert with the tap root to eliminate excessive wiggling, twisting and bending of trunks caused by our southeasterly wind gusts. Many non-native trees never become anchored and suffer a deep South Texas slow death by dehydration as the wind bends and twists that tree, ripping absorbing roots away from the soil particles thereafter denying full water absorption capability. The Texas Honey Mesquite has an amazing ability to regenerate after complete separation of the trunk, branches, twigs and leaves aboveground. Any roots containing bud regeneration zones that are present in the upper 6 inches of soil will regrow a brand new tree that is usually multi-trunked.
When planting your next yard tree, if asked, I shall enthusiastically root for the right native tree to be planted in the right place at the right time, every time!