Thursday, April 28, 2011

Female flowers emerging

     The very first female flowers on pecan trees are starting to emerge from this season's new growth. At this time of year, the male flowers of pecan, or catkins, are the most noticeable flowering structure on the tree. In the photo above, you see numerous catkins hanging down from last year's growth (grey twig).
    From the end of last year's growth, a single new shoot has grown 4 to 5 inches in length. If you look carefully at the very  tip of the new shoot growth, you'll find the female, or  pistillate, flowers (photo at right). At this point the pistillate flowers are not fully formed and are extremely small. The photo below is a closeup of an emerging pistillate flower cluster. Pecan female flower clusters usually contain 3 to 6 pistillate flowers arranged along a single stem (botanically called a spike). A single pistillate flower can be seen at the end of the arrow marked "A".

   It is important to remember that the number of catkins produced by a tree is not an indication of the size of this year's nut crop. It is the number of pistillate flowers produced on a tree that determines potential yield. A full crop occurs when at least 65% of new shoots produce pistillate flowers.

Wednesday, April 27, 2011

2011 Grafting Schools

Come learn the fine art of pecan tree grafting this spring.  We have 4 schools scheduled this spring and all are held at 1:00 pm, rain or shine. Our grafting schools are free and open to everyone.
    Strauss, KS. Friday April 29th. Tom Circle will be hosting this grafting school in his grove located 1 ½ miles south of Strauss on York Road. Drive to Strauss on US HWY 400 then turn south at the corner where Tom has his family's Pecan Store.
    Burlington, KS. Tuesday May 3rd. We will meet at the farm of Brian Williams, 1645 10th RD SE for this class. To find Brian’s farm drive east of Burlington on the paved road for about 6 miles. Turn south onto Quail Rd and drive 1 mile. Turn west onto 10th Rd and drive ¼ mile to the Williams farm
    Thayer, KS. Thursday May 5th. Gary Brennecke and Shawn Schlotterbeck will be hosting a grafting school 2 miles north of Thayer, KS. Our meeting site is located east of the junction of US HWY 169 and KS HWY 47. From the highway junction take KS HWY 47 1 mile east to Elk Rd. Take Elk Rd. north for ¾ mile to the cluster of farm buildings on the east side of the road.
    Paola, KS. Friday May 6th. We will be grafting at Leland Prothe’s pecan orchard at 33795 Victory Rd., Paola. To find Prothe’s Pecans take the 343rd Street exit off of US Hwy 169 just north of Osawatomie, KS and head east. Drive eastwards about 6 miles on 343rd Str. until you find Victory Rd. Turn north on Victory Rd and drive about 1/3 mile to Leland’s farm.

Tuesday, April 26, 2011

Native groves flood

     Spring floods are a normal occurrence in native pecan groves. Yesterday, 4 1/2 inches of rain fell over a period of about 36 hours causing flash flooding on many small streams in the area. As Fly Creek ran over its banks, the native trees pictured above became flooded. Pecan trees can withstand a moderate level of flooding, however floods that last more than 2 weeks will reduce tree vigor. In addition, flooding during the growing season (when trees are in full leaf) is more stressful to pecan trees than if the flooding event occurs during the dormant season.
     In flooded soils, soil oxygen reserves become depleted causing two major problems. Without oxygen, tree roots can't respire (breath) and they stop taking up water and nutrients. During extended flooding events, trees will actually suffer from a lack of water being transported up to the leaves.
    The lack of oxygen in flooded soils also causes microorganisms in the soil to steal the oxygen from nitrate molecules causing soil nitrogen to become depleted in a process called denitrification. I have seen pecan leaves yellow during flooding events due to a lack of nitrogen.
    There is not much we can do about flooding in areas where native pecans grow--it is going to happen. What we can do is ensure that the water moves off the field a quickly as possible by improving the surface drainage within our groves.
      There is one more observation I've made about flooding and pecans.  On a section of my own farm I have allowed native pecan seedlings to sprout up where they wish. What's interesting to me is the distribution of the seedlings across the field follows the flooding patterns I see every time we receive heavy rains. Even though the entire field is located in the Neosho River flood plain, seedling trees seem to be clustered in areas that have a little better drainage (photo at right). The "wet" spot in this field has few or no seedlings volunteering to become a part of my future pecan grove. So it seems that pecans can tolerate floods but don't thrive in soils that are excessively wet. 

Thursday, April 21, 2011

Spring cleaning

    During the rush of harvest there seems little time to clean up fallen limbs and other grove debris. Sure most growers run a stick rake over their groves before harvest, but the piles of sticks and grass remain in the grove all winter long while we concentrate on nut harvest. With the onset of nice spring weather, its time to clean up pre-harvest stick piles and collect even more wood that fell out of the trees over the winter. In the photo above, a stick rake (on the right) is being used to collect the wood that has fallen since harvest and a skid-steer (on left) works to pile the collected wood on a burn pile (note the smoke). 
      It is important to get your brush piles burned as soon as possible. With all that nitrogen fertilizer we apply to native pecans, the ground cover is really growing. It won't be too long until the grass hides chunks of fallen limbs that can rattle both you and your brush hog.

Tuesday, April 19, 2011

Native pecans in early spring

"In every man's heart there is a secret nerve that answers to the vibrations of beauty."
  ~Christopher Morley, 20th century poet and author
    As spring growth emerges from our native pecan trees, the grove is carpeted by the pale flowers of blue phlox, Phlox divaricata. In every season of the year, nothing calms the spirit like being immersed in a native pecan grove.

Monday, April 18, 2011

Pecan tree growth patterns

    Pruning pecan trees can be frustrating. Every spring when you go out to look at your young trees you find 2 to 3 limbs growing every which way but straight up. So you hack away at the tree hoping to create a tree with a strong central leader. The young tree pictured at left is typical--4 limbs all growing from the same general area. Two of the limbs look like they want to be the dominate central leader.
    To prune this tree, I would cut out one of the two upright growing limbs. Leave the limb on the southern side if possible. The second limb I'd remove is the right-hand branch because of its narrow crotch angle. I'd leave the obviously, less-vigorous left-hand branch alone.
    Pruning is made a lot easier if you come to understand why pecan trees grow the way they do. As your trees start to leaf out this spring, take a close look at the terminal growth (photo at right). Believe it or not, pecan has strong apical dominance. Notice how the very top of the tree has already developed new shoots while the buds further down the stem are just starting to pop. As the top of the tree grows, the leaves manufacture a plant hormone that sends a chemical message down the stem to suppress the growth of lower buds.
     Now take a closer look at the emerging new growth (photo at right). I count 4 new shoots all coming from the top 2 inches of last-year's wood.  Leave this cluster of new shoots to grow for the entire growing season and you will end up with the same pruning chore pictured at the beginning of this post, but only two feet higher in the tree.
     You can save a lot of pruning time by addressing this growth pattern early in the growing season. Once the new shoots have grown out about 6 inches, I prune the top to a single new shoot. The easiest way to do that is to locate the lowest shoot in the cluster of shoots and then cut off the stem just above that new shoot (see related post). This removes all the competing shoots above that point and you should be left with one 6 inch shoot that will grow to become your central leader.

Monday, April 11, 2011

Anatomy of a Bark Graft

    Ever stop to think about how truly amazing the process of grafting is? A seedling tree accepts a scion then pushes it to grow a whole new tree crown. I've been grafting for over 30 years but I still stop to marvel when buds start to push on a newly placed scion.
    Recently, I cut down a tree that had been bark grafted five years ago. I wanted to learn a little about the anatomy of a successful graft. After cutting the graft union from the rest of the tree, I used a band saw to slice open the wood. The photo at left shows what the band saw revealed.
     You can immediately see the top of the original stock tree (marked A) that had been trimmed at an angle to promote healing. Also, note the top of the original scion buried under years of wood growth (marked B). This cross section of a graft clearly demonstrates that trees never really heal their wounds, they just grow new wood over the damaged tissue.
    In any orchard of grafted pecan trees, it is usually pretty easy to see a change in bark texture associated with the graft union. Genetic differences between rootstock and scion are also noticeable in the wood. You can see a clear line (marked C) across this tree's trunk that marks the change from rootstock to scion cultivar. Note the line runs nearly straight across the tree at a point where the top of the stock meets the bottom of the scion. The strong dip in the line (marked D) is actually part of the original scion that was slipped under the bark during the grafting process.

Saturday, April 9, 2011

Pecan trees breaking bud

     It is amazing what a couple of warm nights will do to advance bud development in pecan trees. The twigs, pictured at left, show the first stages of spring bud development. The upper bud on the far-left twig is in the bud swell stage. Here the normally narrow dormant bud has ballooned into a large plump bud. Moving down the same twig, you'll see a bud in the a stage we call outer scale split. The brownish scale covering the bud has split open revealing a silvery inner bud.
    As sunlight hits the silvery bud and it continues to expand in length, the bud will begin to green up (right hand twig in photo at left). On mature trees, you will note that the inner bud is actually made up of three buds--the two smaller buds surrounding a larger central bud. The buds on the outside will develop into catkins while the central bud will become a new shoot that will eventually terminate in a pistillate flower cluster.
    Vegetative shoots on young trees produce buds that contain only a single vegetative inner bud.
    The next stage in bud development is called inner scale split (photo at right). As green buds continues to enlarge, the inner scale splits open to reveal either catkins or a new shoot. At this point, the emerging plant structures are still compressed but you can easily recognize what they will become.
     As pecan buds continue to grow you be able to distinguish between protandrous and protogynous cultivars. Protandrous cultivars release pollen early in the pollination season and before their pistillate flowers become receptive. Protogynous cultivars shed their pollen late in the pollination season while producing receptive female flowers early, before they shed their pollen.
     In the photo below, the twig on the left has well defined catkins emerging while the vegetative buds have just begun leaf burst. This twig was cut from a Pawnee tree, a protandrous cultivar. The twig below and to the right was cut from the protogynous cultivar, Kanza. Notice that the two buds on either side of the enlarged, central vegetative bud are still relatively small. Kanza catkins will develop later, well after new leaves start emerging. Look closely at the Kanza vegetative bud (large bud at the top) and you will see that the inner scale has split.
     Following bud break is important for two reasons. First, the pecan tree grafting season begins when the buds enter the inner scale split stage. And second, control measures for pecan phylloxera are timed to specific bud development stages. Insecticide treatment for pecan stem phylloxera should be applied just before innner scale split. Pecan leaf phylloxera sprays should be timed at leaf burst (first leaf unfolds).

Wednesday, April 6, 2011

Promote a central leader

    I've been doing a lot of pruning around the farm, so it seems that every time I look at a tree, I pay close attention to the details of tree form. Some trees seem to have a perfect central leader form--strong straight trunk with well-angled lateral branches (photo at right). This young tree is about 14 feet in height (the pole pruner is 13 feet long) and has been producing a hand full of nuts each fall for the past 3 years.
    For the most part, I like to do most of my pecan tree pruning during the growing season. Summer pruning allows me to shape the way a tree grows much better than dormant pruning. However, during the late dormant period, I like to work on keeping a well focused central leader.
    Here's a close up photo (at left) of the top of the tree pictured above. Looks like I've got three branches competing for the role of central leader. It also appears that I have some pretty strong lateral branches that may try to compete with the central leader.   
    The first step in pruning this tree and to preserve its central leader is to remove two of the three upward growing branches.  Next, I'll remove all lateral limbs within 2 feet of the top of the central leader. Moving down the tree, I will head back some of the strong laterals to reduce competition with the central leader.

    With just a few pruning cuts with the pole loppers, I've redefined the central leader (photo at right).
    This may be the last time I'll be able to preform detailed pruning on this tree. By the end of this summer,  the top of this tree will be out of reach for pruning from the ground. However, because I've worked on building a strong central leader for at least 14 feet in height, I have a tree that should develop a strong, straight trunk that will easily bear the weight of future nut crops.

Tuesday, April 5, 2011

Bark graft maintenance

    Early spring is a good time to look over last year's bark grafts. In the photo at right, you can see that two grafts were applied to this tree last year but only one of the two took off and grew. We left the aluminum foil and plastic bag (applied at the time of grafting) on the tree to protect the graft union over the summer. You can also see a strong wooden stake attached to the tree used to support the graft and prevent wind breakage.
     First step is to remove all wrappings. When I removed the foil, the failed scion just fell off the tree (there was no callous formation to hold it in place). You can clearly see callous tissue formed at the top of the stock where the scion was inserted under the bark (photo at left).
    My second step in maintaining this graft is to trim the top of the stock. If you look carefully, you'll see a distinctive swelling in the stock's bark that runs at a diagonal from scion to the opposite side of the tree--about 1.5 inches down the trunk. To enhance the healing process, I'll  cut the corner off the stock just above that swelling.
    To find the exact angle and location to trim the stock, take your knife and peel back some of the bark on the side of the tree opposite the graft. You'll find that the tree has formed a natural barrier to wall off the wound you created in grafting. Above the barrier the bark will be dark and even decaying. Below the barrier the bark is alive and tan in color. In the photo at right, I'm using a hand saw to cut away the dead wood above the barrier. Note the tan, living bark below the cut. Also note that I'm cutting just above the diagonal swelling in the bark.
     By trimming the stock at the precise location the tree is trying to seal off the wound, you will enhance the healing process and reduce the time needed to keep the graft supported with a wooden stake.
  The final step in early spring maintenance is to prune the tree. Remove some of the lower limbs to force more of the tree's energy into the scion (note the fresh pruning wound below the graft union). Next, prune the scion so you'll have a nice central leader tree.

Friday, April 1, 2011

Target Canker on Pecan

    The tree, pictured at right, stands in a native pecan grove just  down the road from the Pecan Experiment Field. I've always marveled at the numerous cankers that cover this tree's trunk. So, with the sun finally popping out this afternoon,  I thought it a good time to take some photos.
    The canker disease pictured here is commonly called target canker., The target-like concentric rings of callus tissue form as the tree responds to the attacking fungus. The disease is caused by the fungus, Nectria galligena, which seems to infect trees at the site of branch stubs. A large number of cankers weakens the health of a tree and can lead to poor growth and low nut yield. If this tree was in my native grove, it would have been cut down years ago.
    This tree must have read my mind about getting out the chainsaw.  I think it put on this monstrous face just  to frighten me away. (click photo at left to release the monster)