ABOUT PECANS

JUGLANDACEAE

Relatives: Walnuts

There are about 20 or so species of Pecans and these are native to the eastern USA and Mexico. They used to also grow widely in Europe, but most were killed by the last Ice Age, or so the Scientist's believe. Pecan is the main commercial species of these genera. The southeastern Native American Tribes believed the pecan tree was a manifestation of the Great Spirit, and have used the nuts for at least 8000 years. The Crows may have cultivated them and selected good trees with tasty nuts and thin shells to propagate from, so improving their quality. The term 'Pecan' comes from the American Indian word pacane, meaning 'nut so hard as to require a stone to crack'. Pecan trees usually require about a 10 year wait before full nut production. Even so, it is a most important commercial crop in North America. The term 'hickory' is used as a general name for all Carya species, although hickories tend to have harder, rougher shells and are smaller than pecans. They are also hard as heck to crack, and when you do, you only get a small morsel of nut meat. We'll stay with the Pecans, thank you.

DESCRIPTION

Fairly tall but somewhat slow growing (at least initially), Carya illilnoinensis matures into a large and beautiful tree. The bark is gray to gray-black, smooth, and not very thick. Pecan tree branches are not overly strong, so that you will find them 'self-limbing' from time to time. A very, very long lived tree, there are supposed to be some Pecan trees in the deep South of the United States that are about 1,000 years old, and still bearing fruit. That's a good investment: buy a Pecan tree and leave it for your next ten generations to enjoy!
Leaves: Deciduous, pinnate (there is a main nerve, called a midrib, from which the other nerves derive), with multiple (7 - 17) leaflets. The leaves are very finely toothed along their edges.
Flowers: In late spring, they emerge as catkins, and are generally on the scene after any spring frosts. Pecan trees are a bit strange in their pollination habits: the trees are monoecious (meaning they have separate male and female parts), but often when the male is ready, the female is not (or vice versa), and to make matters even more interesting, this can vary from year to year. That being said, to insure a good chance at fruiting, plan on planting more than one variety of tree. Pollination- is done via the wind.
Fruit: Mature, ripe nuts are found in cluster of anywhere from 2 to 10 fruits in late autumn. Before maturity, the fruits are encased in a greenish-black outer husk; at ripening, the husk splits open and the fruit is exposed. The fruit us varies by cultivar but most are in the 1 to 3 inch length. Pecan trees are notorious for bearing well in alternate years- having a meager crop one year and a giant crop the next.

CULTIVATION

Location: Simply put, they grow best in full sun; they do not tolerate marine environments very well. Expect some limb damage in windy areas as the limbs are not very strong.
Temperature: Mature trees grow and produce the best nuts in long, warm growing seasons- hot days and warm nights seem to work best. Sudden changes of temperature can affect Pecan trees.
Chilling: Chilling refers to the number of hours, 45 degrees F and under, during the dormancy period. All fruit and nut trees need a specific amount of chilling hours before they will produce fruit. The amount varies with each variety and the hours need not be continuous. For example as listed: (500 hours).
Soil/water/nutrients: Pecans prefer a deep (they have very long tap roots) fertile soil with even moisture; they may benefit from irrigation in dry areas. Spring fertilizing is a useful practice, particularly on younger trees, and many commercial growers add zinc or magnesium (check to see if you have yellowing leaves).
Pruning: Generally speaking, pruning of your fig tree should only be done while they are young, and then to make a single trunk. Pruning of older, mature trees is needed only for diseased or dead branches.
Pests and diseases: Not too much to worry about here, with the possible exception of Pecan scab, which is possible if there is abnormal humidity or rain in the early fruit stage of development. Powdery mildew and several types of gall are occasionally noted, while here in North Carolina most of our complaints run to bag worms in the upper branches. (The old timers used to take long bamboo fishing poles with kerosene soaked rags on the end and burn the nests out. Now it is much safer and easier to use a hose-end sprayer and a good, environmentally safe insecticide.)

CULTIVARS

There are many good Pecan cultivars out there, but they all have different chilling requirements and do best in different climatic zones. Rabbit Ridge Nursery currently offers the following cultivars, which will do quite nicely in our area and are currently mature enough to begin fruiting now:

(Click on Pecan Variety to link to that Pecan)

PECAN TREE PROBLEMS

When pecan problems occur the cause is frequently not easy to identify. However, once the problem or group of problems is identified, the grower can go about correcting the problem. If the problem cannot be solved, the grower at least knows what to expect and has the option of abandoning or destroying the trees.

The Pecan Tree Is A Survivor

Along the 10,000 miles of rivers and streams in North Carolina there are many very large pecan trees which are living testimony of their tremendous survival potential. These trees have made it through extreme droughts such as the early 1950s where little or no rain occurred for four straight years, yet the pecan survived when other species of large trees died.
If pecans are stressed in the fall, they will not set a large crop the following year, and the tree will survive on food stored in the trees' massive limb, trunk and root system. On weak trees, the crop is shed by various ways throughout the season. This could be physiological drop, pollination drop, casebearer drop or waterstage drop. The shedding of pecans is an important natural stress management tool which contributes to the long survival of pecan trees. It is very difficult for pecan trees to absorb zinc from the soil; consequently, native trees do not make vigorous growth once they are mature and begin bearing. This natural vigor control via zinc unavailability plays an important role in long term native tree survival. Also, many alluvial river bottom soils have good depth, good internal drainage and a very high water holding capacity which are additional reasons native trees are good survivors.

What Kills Pecan Trees

Many things can kill a mature bearing pecan tree. Usually it is a combination of factors. Planting improved grafted varieties on poor soil is the most common reason pecan trees die in North Carolina. When no irrigation, no zinc, no nitrogen, no weed control, no insect management, no disease prevention are combined with a heavy crop on pecan trees growing on poor soil, death could be expected. If a major freeze occurs in the winter, especially early winter, tree death could occur.

Poor Soil Depth and Texture.

Native pecan trees grow beautifully along rivers and streams in North Carolina because of water availability, good soil depth and good internal soil drainage. This is the ideal site for pecans -- native, commercial orchards or landscape trees. In many areas of North Carolina there are deep, well drained sandy or high-calcium clay soils which can also support beautiful and productive trees. However, many soils are too shallow and simply do not provide enough space or volume for the massive root system needed. For example, mature pecan trees require over 2,000 gallons of water per week, and this volume needs to be held by only 25 percent of the soil space. When soils are very shallow or very tight clay, very special management will be needed. Irrigation will need to be weekly and zinc and nitrogen needs to be applied in very small but frequent applications. Commercial orchards should never be planted on shallow or poorly drained clay soils; however, beautiful landscape trees can be maintained, especially if they are natives or seedlings which are not grafted.

Poor Soil Drainage.

The growth and development of healthy pecan trees depends on healthy roots. Good root growth occurs when the soil is 50 percent particles, 25 percent air and 25 percent water. When the pecan soil is dry the tree will survive by shedding the crop and making very little growth; however, when the soil is too wet, the tree roots will die and this can result in tree death. Good soil drainage is essential for good soil aeration and sub-sequential root growth with normal water and mineral absorption. When poor soil drainage occurs there is limited oxygen in the active root zone. This has very serious plant physiological consequences; low root zone oxygen results in death to small roots, reduced active transport of minerals and water into the roots, reduced hormone production by the root tips, and increased salt toxicity. Saturated soil also is an ideal environment for the development of many soil root rot diseases.

Over Cropping.

A very large crop of pecans on mismanaged trees is a major problem. Poor soil, tree crowding, weed control, irrigation, zinc foliage sprays, nitrogen fertilization, insect control and disease prevention is very important to your success. Some growers are lightly shaking their tree trunks on overcropped trees during the waterstage to reduce the crop size and prevent stress. The most common symptom of overcropping is poorly filled kernels. However, when in combination with other limitations, limb death in the top of the tree or total tree death can occur.

Freeze.

The pecan does not have an obligatory rest period such as apple or peach does, and it does not become dormant in the fall unless the weather is very cool. If growing conditions are ideal in the fall, pecan sap remains active. If a freeze occurs, it can kill the live wood, bark and cambium tissue. Bearing trees which are stressed are freeze-susceptible. Young pecan trees which are growing when an early fall freeze occurs can be killed to the ground. This is why nitrogen fertilizer is never applied to young trees after the month of June. Freeze damage usually occurs on the south or southwest side of the trunk next to the ground line. Cutting through the bark with a knife can expose brown, freeze-damaged tissue soon after it occurs. Trees with frozen trunks will produce healthy shoots from the ground line the next growing season.

Tree Crowding.

The most difficult cultural practice pecan growers must accomplish is tree removal when crowding occurs. Shade from tree crowding reduces the total photosynthesis and with less food the tree will be less healthy. The first stage of crowding is low percent kernel. This is followed by alternate bearing and death of shaded limbs. As crowding continues limbs continue to die, moving higher and higher each year. The final stage of crowding is no production or production only in the very top of the tree. Once trees are thinned, as many as six years may be required for the trees to come back into production. Some growers attempt to maintain production via mechanically hedging the trees with large saws, however, this only prolongs the problem. Only 30 percent of the trees' production potential will be harvested from hedged trees when a three- to five-year hedging cycle is used. The solution to tree crowding is tree removal the year the lower limbs touch. It is best to remove trees immediately after a heavy crop.

Cotton Root Rot.

There are many disease which can be serious problems for NC pecan growers. Many destroy the foliage or the fruit; however, Cotton Root Rot kills the tree. Death comes fast in late summer with all the leaves turning brown and remaining on the tree.

Signs Of Trouble

Many times growers have trees which are in trouble but they cannot see it. Consequently, it is good to have other growers, county Extension agents, or pecan specialists look at the trees to see if problems exist. Foliage, crop and tree decline can be slow and hard to recognize if you are in the orchard every day. Problems are slow to become obvious because pecans store food reserves in limbs, trunk and roots. The tree can look healthy to the untrained eye until all of the stored food is utilized, then problems become very easy to see. Signs of trouble can be many. The good news is that these problems can frequently be corrected with good management if the trees are on good soil.

A Brief Guide for Evaluating Pecan Problems

Poorly Filled, Wafer Kernels........................................Soil, Irrigation, Heavy Crop, Management

Kernels with Air Centers and Fuzz...............................Drought Without Irrigation or Other Stress

Green or Black Sticktight Pecans in November..............No Late Season Irrigation or Other Stress

Pecans Sprouting (Vivipary) While on The Tree...........No Late Season Irrigation or Other Stress

Rapid Tree Death in August or Early September.................................................Cotton Root Rot

Blue, Green and Grey Moss (Lichens) on Limbs or Trunks............Shallow Soil, No Management

Little Leaves, Short Shoots................................................Zinc, Soil, Irrigation, Nitrogen, Weeds

Little Yellow Leaves on Young Trees......No New Root Growth, Too Much or Too Little Water

Young Tree New Growth Dies Repeatedly............Root Desiccation or Freeze Damage at Nursery

Small Leaves Which Curve........................................................................................Zinc Deficiency

Leaf Edges Wavy.....................................................................................................Zinc Deficiency

Leaves With Dark Interveinal Discoloration................................................................Zin Deficiency

Shoots Growing Thick in Bunches, Some Dead, Some Alive......................................Zinc Deficiency

Zinc Deficiency Symptoms with Frequent Sprays and Other Good Conditions..................Nematodes

Zinc Deficiency Symptoms with Frequent Sprays and Other Good Conditions.............Sheep Manure

Very Rapid Twisting and Turning Shoots on Young Trees.......................Barnyard Manure Effect

Very Twisted and Distorted New Shoots on Old Trees...........................2,4-D Herbicide Damage

Spring Buds and Leaves Wild and Irregular Shaped............Last Year Roundup Herbicide Damage

Shoots Growing Thick in Bunches, on Trunk, All Alive..........................................Bunch Disease

Nuts Shedding in May with No Hole...................................................Natural or Pollination Drop

Nuts Shedding With Small Hole at Base of Nut............................................Pecan Nut Casebearer

Nuts Shedding in August During Waterstage.....................................Any Stress or Insect Feeding

Nuts Shedding in August with Black Shucks and Half Filled Kernel........................Shuck Dieback

Bark Peeling Off................................................................................No Problem, Rapid Growth

Vertical Splits in the Bark with Yellow Moist Wood Exposed..........No Problem, Rapid Growth

Vertical Splits in the Bark and Wood Which Is Dried Out and Grey.................................Freeze

Perfect Ring or Rings of Small Holes Around the Trunk.....No Problem, Sapsucker Woodpecker

Large Patches of Young Green Bark Missing on New Growth............................Squirrel Feeding

Pecans on the Ground Wwth Holes Punched in The Shuck or Shell..........Bluejay or Crow Feeding

Dead Limbs or Trees, April to June with Sprouts at Ground Line.....................................Freeze

Dead Trunk on South or Southwest Side with Ground Suckers in Spring............................Freeze

Limbs Die Suddenly Followed By Regrowth Which Also Dies.............................................Freeze

Black Spots on Leaves or Leaf Midrib, Black Lesions on Shucks....................Pecan Scab Disease

Brown Dead Tissue Around the Edge of the Leaflet.....................................Chloride, Salt Burn

Sticky Sap or Honeydew Dripping From Shiney Leaves............................Yellow Aphid Feeding

Black and Yellow Areas on Leaflets in August or September..............Black Pecan Aphid Feeding

Leaves Dull Color With Many Small Brown Spots and Defoliation.............................Spider Mites

Black Spots on Kernel.....................................................................................Stink Bug Damage

White Fuzz on Green Shucks..............................................................................Powdery Mildew

White Weblike Growth on Clusters...............................................................................Spittlebug

Galls on Nuts, Cluster, Leaves............................................................................Pecan Phylloxera

Young Tree Dead, Small Holes in Trunk with Sawdust Tube Sticking Out..........Ambrosia Beetle

Small Fat White Grub with Red Head in Pecan.........................................................Pecan Weevil

Small, 1/8" Hole in Shell with Kernel Eaten..............................................................Pecan Weevil

Small White Grub Tunneling in the Shuck....................................................Hickory Shuckworm

Small Limbs Drop in Late Summer or Fall with Perfect Circle Cut in Bark...............Twig Girdler

Mass of Dark Grey Caterpillars Eating Foliage..................................................Walnut Caterpillar

Mass of Thick Grey Webbing Filled with CaterpillarsiIn Late Summer...................Fall Webworm

PLANTING AND INTIAL PRUNING

Below is an excellent link (with pictures) that is worth the time to read. It is short and spot on.

http://extension.uga.edu/publications/detail.cfm?number=B1314#Planting