Fall pecan tree planting

    Last week, during a spell of rainy weather, I drove across the state of Missouri to pick up a load of container-grown trees from my friends at Forrest Keeling Nursery. Once the weather warmed up a bit, I started planting trees.
    The trees I purchased were grown in 3 gallon pots and had tops that were three to four feet tall (photo at right). I prefer planting trees at this time of year to take advantage of the natural flush of root growth that occurs as trees prepare for dormancy.

    When I plant container trees, the first thing I do is remove the container and inspect the root system (photo at left). The fine white roots you see growing in the potting media are the new roots the tree is creating as the top of the tree starts shutting down for winter.
   You should also note the large, circling roots that have developed along the bottom of the pot. Before planting, I like to prune off circling roots to prevent any possible root girdling that may occur as the tree grows larger.

    The photo at right presents a bottom-side view of the root system. Note how the roots circle around the bottom edge of the pot. At this point, I unwind the circling roots and prune them off at the point they begin their circular growth pattern. From past experience with container trees, I know that new roots will be stimulated to grow from the pruned roots creating several new tap roots.

    After root pruning, the tree has plenty of fibrous roots left to absorb water from the soil to help get this tree established in its new site (photo at left). In the past, I've dug up a fall-planted trees the following spring to find that new roots had grown out into the surrounding soil. Emerging from that large root, just behind the pruning cut will be new tap roots. New lateral roots will develop from the current mass of fibrous roots.

    Before planting a container tree, I like to shake off all the loose potting soil from the root ball (photo at right). This helps force the tree to grow into the surrounding soil as soon as possible. Removing the loose potting media will also mean that I can completely cover the root system with soil to help prevent the root ball from drying out too quickly.

     When digging a hole for the tree, I use a shovel to dig a hole just large enough to fit the root ball. The tree should sit deep enough so that when you back fill in with soil you will cover the root ball with about two inches of soil (photo at left). It is important to note that depth of the soil I  use to cover the root ball is basically just replacing the potting soil I shook off.
     I do not recommend using a post hole digger to dig holes for container-grown pecans. Post hole diggers have two major drawbacks. First they tend to dig a hole that is too deep. If a too-deep hole is back filled and a tree is planted on top of the fill, the entire planting hole will settle over the winter and the tree will end up drowning in a puddle of trapped water. The second disadvantage of using a post hole digger is that the spinning action of the auger acts to compact the inside surface of the hole making it difficult for tree roots to grow out into the surrounding soil.

    When back filling soil around the tree, I start by carefully packing soil in around the outer edges of the root ball. Then, I place a layer of soil over the top of the root system. I pack the soil in firmly making sure not to leave any air pockets. Finally, I firm the soil down around the tree with a little foot pressure (photo at right).

   One thing I've learned about planting container-grown pecan trees is that deer will chomp and pull up any newly planted trees. So, before planting another tree, I always protect the tree with a cage made of welded wire (photo at left). These cages are roughly two feet in diameter and four feet tall. I tie the cage to a single steel fence post to hold it in place.

Fall planting of container grown pecan trees

   Every spring I stick a few stratified pecan seeds in pots and grow my own rootstock trees. Today, I took advantage of perfect weather (sunny, low 70's) and moist soil conditions to load up some potted trees in my utility vehicle and head to the field (photo at right). With just about 20 trees to plant, I used a shovel to dig the holes for the trees.

   When digging holes for container-grown trees, I only dig deep enough to hold the entire root system. I used tall pots to grow out my trees so the hole needed to be about 12 inches deep (photo at left).

    When I plant container-grown trees, I shake off all the loose potting soil from the root ball and then place the tree in the hole. I back fill the hole around the tree's rootsystem making sure to crumble the dirt clods as I go. In planting  trees, I always make sure that the entire root ball is covered with soil and it is firmly packed down (photo at right).

    To prevent deer from browsing on my newly planted trees, I always place a welded wire cage around the tree (photo at left). This cage is made from 6 feet of  2" x 4" welded wire and formed into a circle. The cage pictured here is five feet tall but after working with both 4 feet tall and 5 feet tall cages, I've found both heights prevent deer browse. The 4 foot tall welded wire is significantly less expensive so I won't be buying any more 5 foot tall welded wire in the future.

   In making wire cages, I tie the cages in a circle using polypropylene twine (baler twine) (photo at right). This makes removing the cages much easier if the tree grows though the wires of the cage. I tie the cage together in just two spots and can use my pocket knife to cut the cage open and pull the cage away from the tree. I use the same twine to tie the cage to a steel fence post. 

  When driving the fence post into the ground, I always make sure part of the T-post's paddle is showing above the soil (photo at left). By leaving the paddle visible, I ensure that no tree roots will grow over the paddle trapping the fence post under the rootsystem (making it impossible the pull out).
    Hopefully, all my efforts to plant and protect these new trees be successful.  With proper tree care, I expect these trees to be ready for grafting in 2-3 years time. My only problem will be in deciding which cultivars to graft.

Container grown pecan trees: Fall planting and overwintering potted trees

   For the past three weekends, I've been planting the pecan seedlings I started in containers this past spring. Fall is the perfect time for planting container grown trees (photo at right).  For the most part, the soil has just enough moisture to make digging the planting hole easy but is dry enough to allow you to back fill the planting hole with loose, friable soil. Fall planting also allows the roots of the young tree to begin growing out into the surrounding soil almost immediately, helping to decrease transplant shock.

      The trees I planted this fall averaged about 10 to 12 inches in height with an air-pruned root system only about 4 1/2 inches deep (photo at left).  The depth of the root system makes it very easy to transplant--one shovel full of soil and I've got a hole deep enough for the tree. I like to to plant these trees about an inch deeper than they had grown in the container, allowing the root ball to be fully covered with soil. Planting deep ensures that the soil-less media that still surrounds the root system is not directly exposed to drying winds and the tree doesn't desiccate.

     The photo at right gives you a good look at the type of root system that develops inside the bottomless container. The tap root has been air-pruned forcing the development of  a network of fine lateral roots. Once this tree is planted in the field, the air-pruned taproot will re-sprout often creating two or three new "taproots". Next year, my transplanted seedlings will put on just a few inches of new top growth but more importantly, they will be developing massive root systems designed by nature to ensure tree survival.

     I planted about 150 trees this fall but still had some trees left over. With winter's first blast of arctic air forecast for this week, I took some steps to protect my remaining potted trees from the big chill. Although pecan trunks and branches can stand temperatures down to -26 F, the roots of pecan trees will freeze at about +19 F.  This means I needed to take some steps to protect the roots of my remaining potted trees.
    I moved the trees from the nursery bench into my vegetable garden. The garden has two things that makes in perfect for overwintering trees. First, we have raised beds in the garden and the garden paths are just the perfect width for a flat of trees. With a raised bed on either side of the flat, it looks like the trees are partially buried in the soil (photo above).  The garden is also surrounded by a fence that will keep the trees safe from mid-winter rabbit feeding.
    To prevent root freezing, I used a thick carpet of hay packed around the tree flats to insulate and trap the soil's heat around the trees (photo below). 

Pecan seedlings: from simple to compond leaves

  

    As you might recall, I am growing a bunch of pecan seedlings in containers this summer. As my seedlings germinated, the first leaves produced by the new trees had a single blade; very different than the normal compound leaves we see growing on pecan. Now my seedling trees have grown taller they are starting to produce compound leaves (photo at right). The first compound leaf has a large terminal leaflet with only two small leaflets below. Above that, another compound leaf is starting to grow and expand. This leaf will have five leaflets.
    In just a few weeks time, my nursery of container-grown seedling will actually look like a forest of small pecan trees. Before long, every tree should be producing compound leaves.

Pecan seedlings produce simple leaves

    In yesterday's post on growing pecan trees in containers, I presented a photo of nicely-growing, tree seedlings. A copy of that photo is published at right.  Look closely and you'll see that the leaves on these trees don't look like the compound leaves we usually see produced by pecan trees.  The leaves on these seedling trees are simple, appearing as a single elliptical leaf. Are they really pecan trees?
   

   The answer is yes! The first few leaves produced by emerging pecan seedlings are always single bladed. Today, I took a photo of one of my seedling pecan trees (still in the pot) and a normal compound leaf pulled from a three-year-old seedling (photo at right). The leaves don't even look like they come from the same species of tree. However, the seedling in the container will begin to produce compound leaves as it continues to grow. The first compound leaf might have just 3 leaflets, but as additional leaves are produced the number of leaflets will increase.  Eventually, my container grown seedlings will starting looking like "normal" pecan trees.

Growing pecan seedlings in containers

   

    This year I decided to raise some pecan seedlings in containers (photo at right).  There are many successful methods for growing pecan trees in pots but I've had several growers ask me for my recipe, so here goes.
   The process starts with some advanced planning. To germinate pecans effectively, the seed needs to be stratified (stored under cold moist conditions). I like to stratify my seed for at least 120 days to improve uniformity of germination. Details of the stratification process were posted previously on this blog.
 

A germinated pecan seed

     Before talking about pots, soil mixes, and fertilizers, I think its a good idea to become familiar with how a pecan seed germinates and grows in its natural environment. At left is a photo of a germinated pecan. To germinate, the seed must first imbibe enough water to swell the kernel and crack open the shell.  As the seed starts to grow, a vigorous tap root is the first structure formed. Shortly thereafter, a smaller, wiry shoot develops and grows upwards, poking through the soil surface. In nature, a new pecan seedling will invest most of it energy in growing a massive, deep tap root. Above ground, first-year pecan trees rarely grow more than  8-12 inches in height and produce only a hand full of  leaves. This growth pattern is the tree's way of ensuring seedling survival. Between fires, floods, grazing animals and brush hogging, seedling pecan trees often lose above ground parts. By storing a massive amount of plant energy in the tap root, a pecan tree can easily replace a lost top with a new sprout.



   

Tall One pot (4 x 4 x 14 inches) and
 Anderson Band (2.9 x 2.9 x 5.5 in)

     When growing pecan trees in containers, the tree's natural habit of growing a tap root must be considered. If grown in a typical "flower" pot, the pecan's tap root will hit the bottom of the pot, turn sideways and start circling the bottom of the pot.  The subsequent out-planting of pecan trees with circling roots leads to inadequate tree growth and poor long-term performance. To remedy this problem, special "bottomless" pots have been developed to deal with the tap root problem (photo at right).  By bottomless, this means that the bottom of the pot is open, with only a very limited amount of plastic cross pieces present to help hold the potting media in place. When open-bottomed pots are placed on a screen-wire nursery bench, the tap root grows to the bottom of the pot and then becomes "air-pruned". In other words, the tap root hits air at the bottom of the pot and stops growing. However, air-pruning the tap root doesn't stop all root growth. Once the tap root stops growing,  a profusion of lateral roots are created.  
          When I first starting planting pecans in containers I used the "Tall One" style pot but have since switched to the smaller "Anderson Band" container (photo above).  The smaller pot seems to create a denser profusion of lateral roots and makes transplanting in the Fall easier (smaller hole to dig).  There are many other styles and sizes of containers designed for growing tree seedlings (see Stueve & Sons, Inc.). I've thought about trying some of these other pots but then I look at the supply of pots I already have stacked in the barn and  I always decide to stick with what I've got.   

Bottom view of a Anderson Band container

    The photo at left illustrates air pruning of a pecan root system growing in an Anderson Band container. Notice that the tip of the large, freshy taproot has dried out and died after emerging into the air at at the bottom of the pot.  You can also see that limiting taproot growth promotes the growth of small lateral roots inside the pot. 
     I use a totally artificial soil mix for growing pecan trees in pots. The mix I use contains processed pine bark, peat moss, vermiculite, and perlite. Two commercially available soil mixes are Fafard Growing Mix 52 and Scotts Metro-Mix 702. Since these soil mixes have little or no nutrients needed for plant growth, I mix in a slow release fertilizers such as Osmocote 19-6-12 (12-14 months) and "Micromax Micronutrients".  For each 2.8 cu. ft. bag of soil mix, I add 3 cups of the Osmocote and 1/2 cup of the micronutrients before mixing thoroughly. Once the pecan trees have germinated in the pot, I drench each pot with a 1 % solution of "Nickel Plus" to prevent the development of nickel deficiency. A lack of nickel in the potting media is the reason so many container grown pecan trees develop symptoms of 'mouse ear' disorder.

    

    Air pruning the taproot requires that tree pots must be placed on a raised, wire-mesh potting bench. I have used ½ inch hardware cloth tacked onto a wooden frame built with 2x6 treated lumber (photo at left). I raised the bench to a comfortable working height by placing the wooden frame up on concrete blocks.  I planted my seeds around May 1 when temperature finally started to warm up. I set a single nut (on its side) in each pot about 1 inch deep into the potting soil. To make handling the small Anderson pots easier, I use an Anderson deep flat that can hold 25 pots (photo at left). These flats have a very open bottom that holds the pots in place yet preserves the air pruning feature of the open bottom pot.
   One of the disadvantages of using a very porous potting soil is that you will need to water the trees every day. I make sure to completely soak the soil at every watering. During the heat of the summer (temperatures above 94) water the trees in the morning and in mid-day to keep tree roots from over-heating. Heat damage to the roots can be recognized by the appearance of a marginal leaf burn on the foliage.
    I've found that placing my potting bench under the partial shade of two large oak trees has also helped me avoid problems with summer heat. When placed in direct sunlight, the black pots used for growing trees will absorb a lot of the sun's heat causing soil temperatures to rise well above the ambient air temperature. With the combination of partial shade and ample water, I am able to keep tree roots healthy in throughout our Kansas summers.

 I never try to over-winter the seedlings I grow in containers. Pecan roots will die if exposed to temperatures of less than 19 degrees F. Although preventing cold injury to potted trees is possible, I find it more hassle than its worth. I will transplant all my container-grown trees into the field starting October 1st or as soon a soil conditions allow.

Mouse ear and container grown pecan trees

Container grown pecan tree displaying "mouse ear" symptoms

     I like to transplant pecan trees in the fall. Fall planting allows the tree to develop new roots in the soil long before a new flush of leaves starts to develop the following spring. We use container grown trees for fall planting but it turns out that growing pecan trees in a soil-less potting media is not as easy as you might think. One of the most common problems associated with container growing of pecan trees is a nutrient deficiency called "mouse ear" (photo above).

Mouse ear leaf vs. normal pecan leaf

    Mouse ear symptoms include smaller that normal leaves and leaflets that have a more rounded appearance. The photo above illustrates the differences between a leaf displaying mouse ear (left) and a normal pecan leaf (right). 
    Mouse ear is a nutritional disorder caused by a lack of the micronutrient, nickel. Nickel is an important component of an enzyme used by pecan trees to transport of nitrogen from the roots to leaves. Nickel deficiency can be prevented by adding a nickel containing fertilizer to the potting media before planting or by making foliar applications of nickel during the growing season.  A product called Nickel plus has been developed for use on pecan trees. 

Planting container-grown pecan trees

    Planting container-grown pecan trees is becoming an increasingly popular method for establishing new pecan orchards. One of the advantages of using container-grown stock is that trees can be transplanted into the field in the spring or in the fall. In contrast, bare-root trees can only be planting in the early spring.
    The tops of container- grown trees are usually tall and straight but inside the pot, tap roots become contorted and begin circling around the bottom (top photo). To prevent circling roots from girdling the tree in the future, prune the root system before placing the tree in the planting hole. I pull the circling roots down and away from the rest of the root system to find the point where the root is growing straight down. I then prune off the circling portion of the root. You might find 3 or 4 major roots winding around the bottom of the pot. Prune off all the curled roots (bottom photo).
    Once all large circling roots are removed, the tree is ready for transplanting. When growth resumes in the field, most of the tree's energy will be concentrated on regrowing tap roots at the point of your root pruning cuts. The new tap roots will grow straight down, just like tap roots are designed to do. What we usually call transplant shock is actually just a period in the tree's life where root re-growth becomes the primary focus and new top growth is minimized.

Still planting new trees

    We planted a small parcel of land to more pecan trees seedlings yesterday. We used 'Kanza' seedlings donated by Forrest Keeling Nursery and the conditions for planting couldn't have been better. I used my 6 foot wide rototiller to prepare the soil in each tree row. The tilling left the soil lose and fluffy. We prepared the planting holes with a shovel, digging in the loose soil about 3-4 inches deep. The trees we were planting were grown in containers so the first step in preparing the tree for planting was to remove the tree from the pot. Next, I pruned of any circling roots at the bottom and shook off the loose potting soil. We placed each tree in a shallow hole (photo above) and then covered up the root ball with the loose soil from the tilled strip. We mounded up soil around the tree covering the root ball with at least 2 inches of top soil. By planting the trees in these small dirt mounds (about 4-5inches tall) we should help the trees survive next spring's flooding season. Now if we get that 1/2 inches rain promised for tonight, our tree planting efforts should lead to 100% tree survival.