Mid-November cold injury

Osage, 24 Nov. 2014

   Last week we experienced extremely cold temperatures for mid November. On November 18th, we recorded a low temperature of 6 F (the -14 C). So this week, I decided to check the condition of some of our mature, nut-bearing trees.
    Each photo that accompanies this post shows the bark peeled back on a fruiting shoot (on the left) and a vegetative shoot (on the right). The caption below each photo identifies the cultivar.
  

Kanza, 24 Nov. 2014

Chetopa, 24 Nov. 2014

Maramec, 24 Nov 2014

    In peeling back the bark of several cultivars, I found a range of cold
injury. Osage, which produced a light crop this year, had a healthy green color inside the bark. Kanza and Chetopa showed signs on internal browning while Maramec was severely injured by the cold.
     In looking at the Kanza shoots you will note that the fruiting shoot appears to have more internal browning than the vegetative shoot.  I noticed this same relationship between fruiting stress and cold injury with Pawnee last year. In contrast, Chetopa shoots seemed to have the same amount of cold injury regardless of shoot type.
    Both Maramec shoots displayed severe internal browning. However, the fruiting shoot appeared to have suffered greater cellular freezing.
    In years past, I have seen cold injured trees break bud normally in spring and set a good crop of nuts. Pawnee trees injured last winter produced a good crop this fall. It will be interesting to watch how cold injury in mid-November impacts flowering and fruiting next spring. I have the feeling that Kanza and Chetopa will overcome the damage they suffered and produce nuts next year. Maramec may be in trouble for 2015.

Kanza performance 2014

2014 Kanza crop

   If you have been following this blog for some time, you know that I have been documenting the yield and performance of a three acre block of Kanza trees. This year we harvested a good crop of nuts, averaging 1268 lbs/acre (see table below).  
     In looking over the records for this block of trees, it is interesting to see the impact of below-average rainfall on tree performance. During the years 2011, 2012, and the first half of 2013 the trees suffered from serious water shortages. Drought conditions impacted tree grow rate, nut weight, and yield. In 2013, mid-summer rains helped to increase nut size but yield had already been impacted by the previous season's drought. You see, each spring's pistillate flower production is largely determined by growing conditions during the nut filling period the previous summer. 

   

Cracked Kanza nuts, 2014

    In 2014 tree grow rate responded to better soil moisture conditions and total pecan yield increased. However, the dry spell we experienced in mid- summer decreased nut size and increased the number harvested stick-tights.    
    Over the years, we have progressively thinned this Kanza block as trees begin to crowd. The thinning plan for this orchard and our tree removal progress has been posted to this blog. When planted, this block of trees contained 144 trees spaced 30 feet by 30 feet. So far we have removed 17 trees but the thinning plan calls for the eventual removal of 72 trees in total (resulting in a 42 ft. x 42 ft. spacing). However, by taking a thin as needed approach to tree thinning,  we have maintained total block yield despite experiencing problems with drought.

Grafts survive cold snap

    When I woke up this morning the temperature outside had dropped to 6 degrees F (-14 C). For mid-November that's pretty darn cold. When I drove by some of my young pecan grafts today, I noticed some of the leaves were still frozen on the tree (photo at right). These leaves had frozen back on November 4th during our first hard freeze, but when leaves remain on the tree it indicates that those branches had not fully hardened off in preparation for winter before the cold weather hit. With the extreme cold this morning, did my young grafts suffer cold injury?

   To check for winter injury, I took my pocket knife out and cut into the main stem of the graft and peeled back the bark. Winter injury on pecan first appears as brown streaks in the  inner bark. The inner bark of this tree was healthy and green (photo a left). The two small, circular, brown spots you see on the inner bark are wounds caused by insects that feed on the stem last summer. 

    This young graft had several, small-diameter shoots at the top of the tree (see photo above). These shoots had developed in mid-summer as a result of a second flush of vegetative growth. This was also the portion of the tree that was still holding on to its frozen leaves.
    Were these shoots injured by the extreme cold? To check, I cut into the wood for look at the inner bark (photo at left). I found nice green inner bark. At this point in time, this Kanza graft looks in good shape.

   Early this year, I decided to top-work a few Jayhawk pecan trees to some new cultivars. When you graft such large trees, the scions grow extremely fast and tall. Vegetative growth can continue late into early-Fall and that new tender growth can be prone to winter injury. The photo at right is one of the top-worked trees I grafted last spring. The graft union is painted white and the scion grew a healthy five feet in height this past summer. Note that the branches below the graft have lost all their leaves while top of the new graft has leaves frozen in place. I needed to check this graft for cold injury.

   I cut into the stem of the new graft and peeled back the bark. The inner bark was still green and healthy (photo at left). No cold injury here.
  

Winter arrives in mid-November

    Last week we harvested a lot of pecans despite the below normal temperatures. Conditions were dry and the harvest machinery was working great. Unfortunately, 3 inches of snow fell yesterday and the grove was blanketed in white (photo above). It will take some time before the snow melts and the ground dries enough to resume harvest. In the mean time, we'll be in the barn running harvested nuts through the cleaner.