Monday, December 30, 2019

Giving pecan trees room to grow

   To maintain good nut production, pecan trees need plenty of room to grow and develop a full canopy. When I established my pecan breeding block, I planted trees far closer than normally recommended to allow for the evaluation and selection of new cultivars. As the trees started to produce nuts, I started to remove trees that produced small nuts or displayed poor resistance to pecan scab disease. This project started with over 800 trees but currently, I've already removed 90% of the original trees.
     This winter, I'm back thinning out more trees (photo at right). At this point in the project, my tree removal objective is to make certain that trees that have the greatest potential to become new cultivars have plenty of room to expand their canopies. The trees in the photo were growing only 20 feet apart within the row (row spacing = 40 feet)  with adjacent canopies shading each other. After tree thinning,  the remaining trees will be spaced 40 feet by 40 feet.

      The photo at left is an example of the nuts produced by one of my selections that I have made a priority for ensuring adequate tree spacing. In fact, tree KT334 is pictured above as the first tree in the row at the left side of the photo. Now that KT334 has a more normal tree spacing, I'll be able to get a better feel for its production potential.

Thursday, December 26, 2019

Preparing pecan seeds for planting next Spring

    Next summer,  I plan to grow some pecan seedlings from seed so I can eventually expand my pecan orchard.  The seed I'll be using this year came from my pecan breeding block and is basically all the nuts that were too big to fit in my pecan cracker (size 15 pockets). I'm sure I'll get a lot of variation in seedling vigor from this seed source but I plan to rouge out any runty seedlings by mid summer.
    Pecan seeds need to go though a process called stratification before they will germinate properly. I start this process by placing all my seed in a large plastic tub (photo above).

    Next, I fill the tub with water and allow the pecans to soak overnight (photo at left). The pecans will float to the top. To ensure that all the nuts stay submerged in water, I place another plastic tub (same size) on top of the nuts then weigh it down with additional water to press all my seed nuts under water. Only fully hydrated seed will sprout into trees.

     Pecan seeds also require a chilling period to release them from seed dormancy. However, the seeds must not be allowed to dry out while in cold storage. To accomplish this, I line the bottom of a plastic storage container with moist potting soil (a mixture of peat moss and pine bark), then place a layer of well soaked nuts on top (photo at right).

    I then cover then nuts with a layer of more potting soil. I make sure all the nuts are fully covered (photo at left).
     Next, I add more pecans on top (photo at right). Once I create another layer of seed nuts, I'll cover those nuts with another layer of potting soil. I repeat the process until the box is full and the final layer of seed nuts is covered by potting soil.
    I ended up getting 4 layers of seed nuts in each storage box (photo at left).
    The final step in seed preparation is to label the seed box with the date the seed will begin their cold treatment (photo at right).  Yes, I was stratifying pecan seed on Christmas day. The sun was shining and it was over 60 degrees outside. I couldn't think of a better present to give my family than the promise of a new pecan orchard.
     The final step in the stratification process is to place the seed boxes into cold storage. Pecan seeds need to be held at 33 to 40 degrees F  for 90-120 days before they will germinate uniformly. If you use a standard household refrigerator to stratify your seed, open the lid of your seed box once a month to make sure the potting soil isn't drying out. If the soil feels dry, simply sprinkle on some water to re-wet.  
    My seed nuts should be ready for planting in late April just as outdoor temperatures start to warm up. 

Wednesday, December 11, 2019

Top-working a pecan: Reasons for failure and an appoach for next spring

    Recently a California pecan enthusiast sent me a photo of his failed attempt at top-work a fairly large pecan tree (photo above). He had found my pecan blog online and solicited my advice on how I would approach grafting his tree. Rather than just replying to his email, I though his photo could prove to be a good learning opportunity for many of my readers.
   I'll start by pointing out why I think things went wrong. From what I can see, 9 grafts were attached to this tree, each covered in a paper bag, and scattered among terminal branches. From the photo, I cannot tell which grafting technique he employed but I do know that every graft failed. The biggest mistake made in grafting this tree was that not enough of the tree was cut back to force a graft to take. Applying a graft out on the end of a branch simply allows too many places for the tree to grow around the cuts made in grafting. Ultimately, the tree just walls off the scion like it was a broken twig. In addition, I am not a fan of placing a brown paper bag over the graft union and scion. Rather than shading the graft as intended by this method, the bag can cause the scion to get too hot, baking in the every present Southern California Sunshine. Thirty years ago, I visited a commercial nursery that was bagging every pecan graft. I recommended dropping the bagging process and their grafting success increased dramatically.

   Now lets look how I would approach grafting this tree next spring. Before making a single pruning cut, I would make sure to obtain some good scionwood cut from a vigorous one-year-old shoot. I would top-work this tree with a single bark graft, so great scionwood is critical. When leaves start to unfurl next spring, this tree will be ready for grafting. In the photo above, I have drawn in the pruning cuts I would make. The cut labeled "A" is the location where I would place a bark graft (directions for bark grafting can be found Here). I would also remove the large 3-forked branch marked "B" to make sure all of the tree's upward growing energy is directed to the graft union. I would leave all the remaining lower lateral limbs in place to shade the trunk and provide valuable leaf area to help feed the root system. In addition, I would also do a little detailed pruning by removing any small branches that are growing strongly upwards (cuts marked "C"). In fact, all summer long I would return to this tree to make sure that the lower lateral limbs only grow outwards not upwards. 
      After inserting a bark graft into the top of the central leader, I would be certain to attach a 8-foot-long training post to the trunk so that it extends 5 feet above the scion. My goal for this tree would be to get 5 to 7 feet of new growth from the scion during the first summer so I'll need a good sized training stick to support the scion and prevent wind damage.

Saturday, November 30, 2019

A split pecan shell can be a sign of trouble inside

    Over the past week, I've been staring at thousands of pecans moving down the pecan cleaner belt. Cleaning the crop may be monotonous but it all part of the fun of pecan growing. While cleaning pecans, I always look out for anything that's unusual. I'll pull off a nut that sparks my interest and set it aside for closer inspection later. This year, I noticed several pecans that have split shells (photo at right).  There can be several causes for the shell to split open along the suture; sometimes the reason is obvious, other times you will need to open the nut to pinpoint the cause.

    The split pecan pictured above is an example of a nut that started to sprout (form a root) while still on the tree. This condition is known as Vivipary. When this nut crossed the cleaning table, I could see the dark, dried up root sticking out of the nut's apex. Using my knife, I split the nut completely open to reveal what premature nut sprouting does to kernel quality. The blackening of the kernel would make this nut completely unsaleable.

    The nut pictured above is a not-so-obvious example of vivipary. In the split, near the apex, I noticed a very small piece of dark tissue. When I split the nut wide open, I found that this nut had only just started to sprout. It is most likely that the root tissue of this nut and the root of the previous example of vivipary were killed by the extreme cold temperatures we experienced in early November (14 degrees F).

     Some pecan cultivars have genetically weak sutures and are to prone to splitting open as the kernel fills the inside of the shell. The pecan pictured above is an example of  a weak suture that allowed fungi to colonize kernel tissue. This is especially a problem during wet fall weather when pecans sit on the ground for weeks before they can be harvested.

    The final example of a split shell reveals that not all pecans with split shells turn out to have defective kernels. Now that this nut is harvested and held in a cool and dry place, I wouldn't expect the nut to become infected with kernel rotting fungi. But, if this nut was still sitting outside under a pecan tree, the split shell would make this pecan prone to picking up a kernel rot. 

Wednesday, November 27, 2019

The price for not controlling pecan scab

     2019 will be a year remembered in our area for its unusually frequent rain-showers. It rained all summer long and that weather pattern has continued into pecan harvest season. Only a fraction of the native pecan groves that grow along the Neosho river have been harvested. However, with much of the crop still hanging on the trees, I had the opportunity to photograft some of this year's native nuts (photo above,  right).   
    The first thing I noticed was that many of the hulls have not opened up, or if they had, opening was incomplete.
  Looking over the nuts on a single tree, I found entire clusters of stick-tights (photo at left). The shucks of these nuts never opened up because they were severely infected by pecan scab during our wet summer months.
   On the same tree, I could find nut clusters that had open shucks. However, even the shucks that had opened showed signs of scab infection (to a lesser extent than stick-tight nuts). To illustrate the impact of scab on native pecan yield, I collected nuts from open shucks and nuts from stick-tights.
    The photo above shows the nuts (top) and kernels (bottom) of the pecans I collected from open shucks as compared to stick-tights. On average the nuts peeled out of stick-tights were smaller than those pulled from open shucks. The kernels of open shucked nuts were well filled and plump. Kernels pulled from stick-tight nuts were often shriveled and dark.
   Commercial pecan growers always discard stick-tight nuts during the nut cleaning process. So in effect, scab causes total economic loss from heavily infected pecans. This year, native pecans required a strong fungicide program to prevent major crop losses. Our native trees set a heavy crop in 2019, but with the widespread outbreak of pecan scab, less than 50% of those nuts will be marketable.   

Tuesday, November 19, 2019

Finally, pecan harvest underway

    Last week we saw temperatures plunge into the lower teens. Then we finally experienced a string of dry weather days. These factors, combined, have allowed me to go full throttle on pecan harvest over the past several days.
     The deep cold helped to freeze dry the shucks which allows the nuts to fall freely during tree shaking (photo of Kanza nuts at right). The dry weather was needed because we've had so much rain this fall that the soil in the pecan orchard was saturated. And, you just can't pick pecans on muddy ground.

   I started harvest this year by identifying areas in the orchard that had the driest soil conditions. I use a Savage pecan shaker equipped with doughnut pads to remove the nuts from the tree (photo above).  This year, the nuts are easily removed with just a quick touch on the throttle to ramp up the shaker. I just love the sound of nuts raining down on the canopy of the tractor. It reminds me of all the great pecan harvests I've seen in the past.
   After shaking I used my pecan harvester to sweep the nuts up off the ground (photo at right). These pecan harvesters are great at picking pecans but if the soil conditions are too wet they will also pick up mud. This is why I started harvesting trees growing in the drier spots of the farm. After 4 days of drying weather, I've gotten over 80% of the farm but unfortunately it doesn't look like I'll get to those wetter spots before the next round of rainy weather sets in.
   Thankfully, I now have an ample supply of nuts picked up and safety stored in the barn. On the predicted rainy days ahead, I can begin cracking nuts to supply new crop pecans for my wife's roadside fruit market.

Friday, November 8, 2019

Hard freeze will allow full pecan shuck opening

    I woke up this morning and checked my thermometer. At dawn, it was 22 F (-5.5 C), cold enough to freeze both leaf and shuck tissues. By mid-morning I could see pecan leaflets dropping from my trees.  The photo at right shows a Gardner pecan tree still holding on to most of its leaves. However, the leaves have the dull green cast of freeze killed tissue.

    As I stood watching, green leaves were falling off the tree. After several camera shots, I was able to capture a flurry of leaves as they blew off the tree (photo above). Note the litter of green leaves on the ground, while a strong south wind sent several leaflets airborne.

    The hard freeze also impacted the pecan shucks. The photos above show a Kanza nut cluster before and after the 22 F freeze. A few days ago, Kanza shucks appeared to be drying very slowly. Although the shucks had split, the nut was still closely held by the 4 sections of the hull. This morning the shucks looked only slightly different. The outside surface of the shucks appeared wrinkled and the hulls were beginning to pull away from the nut. The freezing temperatures caused the cells of the shuck tissue to rupture allowing water to escape and the hull to start drying more rapidly. In a few days, a lot more of my Kanza pecans will look like the cluster pictured at right.    

Thursday, October 31, 2019

Cold wave freezes pecan tissues

   The weather this week has been miserable; Rain, drizzle, and cold temperatures. A late night cold front finally pushed through SE Kansas early this morning and cleared the clouds away (at least for a few days) but ushered in sub-freezing temperatures.  The thermometer read 27 degrees F this morning at dawn, so I was curious to see if the leaves and shucks of my pecan trees would display signs of cold injury.
   This afternoon I walked out to some Kanza trees and found that many leaves looked freeze dried but were still hanging onto the tree (photo at right). Frozen pecan shucks typically appear water soaked after a hard freeze but this morning the shucks looked just like they had last week.

   During previous fall seasons, a morning low temperature of 25 degrees F would cause the leaves to drop off the trees by noon and the shucks to become water-soaked and dark immediately. However, it appears that 27F is just not cold enough to cause total vegetative tissue destruction.
    I'll be interested to see how my trees react over the next few days as temperatures climb back up into the 50's. I expect to see partial defoliation but I'm afraid the shucks will continue to hang tight around the nuts preventing them from falling freely.
    With the soil under my trees rain soaked, it looks like it will be some time before I can start shaking trees and harvesting nuts. But, gosh darn,  its hard being patient. 

Wednesday, October 16, 2019

Making a Fall fertilizer application

    The soil on my farm has finally dried out enough to allow me to make a Fall application of fertilizer to my pecan orchard (photo at right). I like to fertilize in October for two reasons. First, pecan tree roots are making their Fall flush of new growth and fertilizer is most rapidly taken up by new roots. Secondly, adding additional soil nutrients at this time of year helps the tree recover from the stress of nut production before the start of winter cold (helping to avoid possible winter die-back).
  Today, I applied 53 lbs/ac nitrogen, 38 lbs/ac phosphorus, and 50 lbs/ac potassium.  Including the cost of spreader rent, I invested about $64 per  acre for this fertilizer application. That sounds like a lot of money but making regular fertilizer applications is the best way to build tree health and ensure regular nut production.
   I plan to spread additional fertilizer in the early spring of 2020. In my experience, twice-a-year fertilizer application has proven to help reduce alternate bearing and increased overall yield.

Monday, October 14, 2019

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.

Tuesday, October 8, 2019

Pecan cultivars ripening in early October

Oswego, 7 Oct. 2019
    During early October more pecan cultivars ripened. On my Monday-Wednesday-Friday trips through the orchard, I recorded more shuck split dates for several cultivars and selections in my breeding program. Once again, I present photos of recently ripened cultivars and a few photos of selections from my breeding project. The date of ripening is given in each photo's caption.

Lakota, 7 Oct. 2019

USDA 64-4-2, 4 Oct. 2019
KT334,  4 Oct. 2019
KT158, 7 Oct. 2019

KT201, 7 Oct. 2019

Wednesday, October 2, 2019

Pecan foliage diseases

    While driving into Chetopa, I've noticed a native pecan tree that has already shed most of its leaves (photo at right). I stopped the truck and walked down into the grove to investigate. Turns out, this native tree was especially susceptible to pecan anthracnose and the disease has prematurely defoliated the tree.
    The combination of a wet summer and no fungicide applications has allowed pecan diseases to run wild in many native pecan groves this summer. I spent some time today taking some photos of some common pecan diseases.
   First up is Brown Spot (photo at left) caused by the fungus Sirosporium diffusum. This is a fairly common late season leaf disease during years of high late summer rainfall. I have only seen this disease in orchards that do not receive regular fungicide applications during the growing season.

    The photo at right shows a pecan leaf with several diseases. The dark black lesions along the midrib of the leaflets is cause by Vein Spot (Gnomonia nerviseda). The  brown leaf scorching of the leaflets is caused by Pecan Anthracnose (Glomerella cingulata) and the brown spots on the leaf blade were caused by the brown spot fungus.
     Pecan anthracnose infected nuts are often confused with pecan scab infects nuts. Nuts infected by anthracnose in mid-summer will turn dark brown, stay small in size and often partially split shuck (photo at left). However, the shucks on the small nut pictured at left with never release from the shell. Nuts infected later in the summer will gain full size but the brown shuck will be slow to open in the fall.
     I also found Powdery Mildew on some nuts. The fungus, Microsphaera penicillata, causes a white powdery substance to form on the surface of pecan shucks. The disease seems to have little impact on nut fill or shuck opening.
    I started this discussion on pecan diseases all because I saw a native tree completely defoliated by the middle of September. The photo at left shows a pecan terminal that has already lost a significant number of leaflets due to anthracnose. As leaves loose their ability to photosynthesize due to disease infection, the tree sheds the damaged foliage. If disease induced defoliation is severe enough, the tree will simply shut down for the season and go into early dormancy. Trees suffering from early defoliation produce few or no nuts the following growing season.