July is the month that you can finally look up into a pecan tree and notice nuts hanging from branch terminals. At this point during the growing season, pecans have entered their rapid growth phase, when nuts grow in size and the kernel tissues begin forming. Pictured at right are some nuts I harvested today from four cultivars. I chose these cultivars because they range in nut maturity date from very early (Osage) to late (Maramec). At this point in the season, the nuts of all 4 cultivars are roughly the same size but slicing open each nut shows that the progress of kernel development differs. While the nut is expanding, the kernel inside is composed of the seed coat and liquid endosperm (looks like water).
At the start of nut enlargement, the seed inside the nut is small and heart shaped (like the Maramec nut pictured above). As the kernel expands, the seed coat expands downward towards the base of the nut and you can see two kernel halves start to develop (Osage nut above). Cutting nuts open at this time of year can give you a pretty good idea when nuts will ripen in the Fall (at least in comparison to other pecan cultivars). In the photo above, I've arranged the four cultivars in order of ripening. Osage ripens earliest, followed by Kanza, then Greenriver, and finally Maramec.
While I was out collecting nut samples, I decided to pull some nuts from 3 cultivars that are relatively new to our cultivar collection (photo at right). Judging from the size and shape of the kernels, Hark and Yates 68 should ripen about the same time as Kanza. The kernel development of Surecrop looks to be closer to Greenriver.
We may be suffering through the dog days of summer, but cutting open pecans in mid-July only makes me optimistic for a good pecan crop this fall.
