Thursday, July 23, 2015

A preview to nut maturity date

16 July 2015
     Last week, I collected group of well known pecan cultivars to check on the progress of nut development. Sometime during the month of July, all pecan cultivars enter a phase of rapid nut expansion. In a previous post, I outlined the phenology of pecan fruit development and made the point that early-ripening cultivars start sizing earlier in the year, fill their kernel earlier in August and take less time ripen following full kernel development.  
    In the photo above, I've arranged 5 cultivars in order of the expected ripening date this fall. Faith will split shuck in late September while Stuart won't mature until late October.
   By cutting open each of these nuts, you can see that the kernel is just starting to develop inside each of these nuts (photo at right). The Faith nut has the most advanced kernel and is in the large heart stage. Kanza and Oswego have developed small heart shaped kernels while Giles and Stuart kernels are still oval in shape. Rapid nut expansion doesn't really start until the kernel takes on the small heart shape. This means, by mid-July, Giles and Stuart are already significantly behind in the race towards nut maturity. 

16 August 2015
   Now, let's look at a few cultivars that we haven't had years to study (photo at left). The first thing I notice is that two cultivars, Surecrop and 75-8-5 are much plumper than the others. City Park, a large blocky nut at harvest, looks small and thin at this point in the season.  

       I cut these nuts open to check on kernel development and allow me to compare this second set of nuts with the first.  USDA 75-8-5 had the largest kernel growing to 1/4 water stage. Surecrop, Lakota, and Gardner (sorry for the bad cut on Gardner) were all in the large heart stage. City Park was just approaching the small heart stage.
   What does all this mean? It means that USDA 75-8-5 will ripen in late September at our location.  Surecrop, Lakota, and Gardner will ripen in early October. City Park will be the latest to ripen sometime in mid-October.