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. 

Pecan germination in the shuck

   Vivipary: A ten dollar word that describes the premature germination of a pecan in the shuck during the Fall of the year.  Normally, pecan seeds are fully dormant in October and require a 90-day chilling period to stimulate germination. However, a heavy nut crop and unusually warm, moist, weather conditions during shucksplit can trigger vivipary. In the photo at right, the yellow arrow points to a pecan root emerging from a recently harvested pecan. When a sprouted pecan is harvested and dried under normal harvest conditions, the little root dies and the embryo inside the shell decays. Ultimately, embryo rot totally destroys the value of the kernel.
    Fortunately vivipary is a rather rare phenomenon in northern pecan areas. This year I've found only 2 sprouted nuts among the thousand of nuts I've collected for evaluation this winter. Most years I never see vivipary at all.

Vivipary

    Vivipary is the word we use to describe the condition when nuts start to germinate in the fall while still encased in the green shuck.
 Vivipary is a major problem for pecan growers in the most southern regions of Texas but rarely occurs in the north. This year, however, I've come across more premature germination then usual. This morning, I even found a hican sprouting on the tree (note the root emerging from the nut at left). Now, while vivipary is still not a major problem in our area, it is worth noting because by the time we sell the 2010 crop you may see some embryo rot in your nut sample. This rot occurs when the germinating embryo dies from lack of moisture and fungal attack through the split shell.