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Milberger's Nursery and Landscaping
3920 North Loop 1604 E.
San Antonio, TX 78247

Open 9 to 6 Mon. through Sat.
and 10 to 5 on Sun.

Three exits east of 281, inside of 1604
Next to the Diamond Shamrock station
Please click map for more detailed map and driving directions.

Click here

Larry Stein, Professor and Extension Horticulturist
Texas Cooperative Extension

The dawn of a new pecan harvest is upon us once again. Some are rejoicing after battling the 2005 vicious summer elements of heat and drought for the last four months, whereas others are wondering how it could already be that time. Others are worried about the high price of fuel and what that is going to do to their harvest costs while some are pondering the potential price.

Regardless, most are in the process of getting ready to shake their first tree which means that not only must equipment be readied, but also the native bottom floor must be prepared. It is probably too late to do any serious leveling but armadillo holes ought to be filled at the very least. Not only do the holes capture nuts, but they can bounce tractor operators right off the seat. As everyone knows a firm "floor" is needed to mechanically harvest.

One of the pressing issues at hand is the removal of broken limbs and branches and one of the nagging questions that remains is "Why do these limbs fall?" Everyone has heard the expression, "so and so fell and broke their hip." But in reality in almost all cases the person's hip broke and then they fell. In the case of trees, there is no question what breaks first, but the reason is far from being clear and in most cases, there can be numerous reasons and more often than not is a combination event. Potential reasons for limb fall include: crop load, "breach" of the bark, wind, maybe drought, trapped bark, "shading out" and age.

Even though it is common for humans to lose strength as they age, age itself does not necessarily make wood more prone to breakage.
But one can liken a mature tree to an aging house; as the house ages there is potential for the roof to leak, the plumbing to break, and various things to wear out. Still the strength of the wood is the same, but the stress and rigor from various outside forces are at play on the tree. As a young tree, limbs are vigorous and strong. It is nothing for the tree to carry 50 to 60 pounds of pecans. As the tree ages it sets and carries more pecans until one day the limit of some of the branches is exceeded and a branch here and there snaps in two which successfully "breaches" the tree's protective mechanism of the outer bark. The most ideal thing to do when a limb breaks is to saw the rough, jagged broke area smooth and in such a way that water is shed and cannot accumulate in the wound. Still who in their right mind is going to climb a 120 foot native tree with no safety net to correct one of these wounded areas. Trees will wall off the area and they do a good job; it is just that it is almost impossible for a tree to completely cover a rough area. So over time water accumulates and before long the heart wood (non-living portion of the tree has begun to rot). Over time this rotted area grows bigger and eventually another limb falls.
Realize we are talking tens of years and more, but it happens just the same. In some cases the initial breach may have occurred 30 years ago.

Pecan has also been accused of having "brittle wood," especially as it gets older. I don't subscribe to this theory and in reality where the brittle wood theory comes from is probably due to "shading out."
Pecan is a sun loving plant and leaves on branches must receive full sunlight to remain healthy. As trees get larger and branches begin to touch, the lower limbs receive less and less light and over time they die! As a result, it is not uncommon for limbs to come "raining out" of these older native trees. So is the wood brittle? Yes, but only because the limbs were already dead. If all pecan wood got brittle with age, none of the famous human pecan threshers would have survived.

Trapped bark can be a problem when limbs form "V" crotches.
Over time the bark accumulates in the "V" causing the areas to be weak.
A good crop of nuts, leaves or a wind can bring this limb to the ground again breaching the bark.

Drought has been rumored by some to be the culprit of limb breakage. There is no question that pecans are large users of water.
Most of the water is simply lost as water vapor via transpiration.
Pecans are not one to rapidly close their stomates due to fluctuations in light, hence water loss continues as long as the tree has access to water. As water becomes limiting the stomates close, and eventually leaves will scorch due to the lack of water. In severe cases the tree dies back to what it can support. Many of the fallen limbs which were blamed on drought have a very healthy crop of leaves meaning water was not limiting. So in my opinion, drought is not causing the limbs to weaken and break. What is really interesting about these limbs is that usually they break when it is dead still. One would think it happens in a wind storm, but this is generally not the case. In some cases crop load again is the cause, but sometimes the limb is barren. More than likely the answer lies in a breach of the bark.

Realize that breaches in the bark can occur for many reasons.
Hail can be especially hard on trees. Most times the wounds heal, but a small hole may remain. Eventually water can make the hole larger, or it can be gnawed around on by a squirrel. Woodpeckers also do their share of breaching the bark. So what was a small hole gradually increases in size. Water accumulates in the area and the wood rotting mechanisms are set in place. Over time squirrels hollow out the area and it grows.

Growers take care of their trees with fertilizer and zinc and not only do the trees put on a heavy crop of leaves but also a good nut crop. As the nuts begin to fill in August, it is simply too much for the limb to carry and the branches come tumbling down. So it is an on going process typically started by a simple event. The good news is these trees have been around for hundreds of years, more than 300 in many cases, and guess what, they are going be here long after us. They are resilient in nature and will recover. So don't dwell on the why the limb broke and the amount of pecans you lost, simply move on; clean the limb up because just as soon as you think you are done, another will be down to take its place.

Some limb loss you can blame directly on crop load; there is simply a limit as to what a branch can hold. Other losses are from a combination of factors including the wind, but in the end it is those small, seemingly insignificant breaches in the bark which leads to more limb loss. Many times such limb loss can be used as an opportunity to remove trees as tree crowding is one of the greatest challenges which
native growers must continually address.