Harvesting Cross Pollinated Chestnuts

January 31, 2006

The 2005 harvest of nuts, produced by cross pollinating 100% American chestnut trees with hybrid pollen supplied by Meadowview Farms, involves collecting burs, extracting nuts, recording the results, and storing the nuts until planting in the early spring can occur.

A tree such as the Max Kimmel, 100% American chestnut tree is hand pollinated in the spring and has burs ready to harvest in the early fall.  The burs are contained in paper sacks which have been sealed around the stem to insure no other air born pollen contaminates the hand pollinated burs. As a control, certain burs are not hand pollinated and are sealed inside a bag. No nuts should be produced in the burs in the control group.

Extracting the nut or nuts growing within the bur requires opening it. The bur pictured has naturally opened. The harvested burs are picked green when the nuts are mature and before squirrels are attracted to the tree. Opening the green burs requires great care as they have sharp spines.  The collected burs are “shucked” at a station supplied with the shade of an umbrella, bags of harvested burs, and material for storing the harvested nuts.

The “shucking” station is equipped with heavy duty rubber gloves to use in handling the burs, a knife to use when necessary to open the burs, sphagnum moss and water to moisten it with, and sealable plastic bags in which to store the sphagnum moss and harvested nuts. Most important, records are kept of the results of the harvest.

The results of the nut harvest from the Max Kimmel are documented carefully.  Data classifying the 100% American chestnut parent, the source of the pollen, the resulting crop of nuts, including the control group, are recorded. The information is entered into a computer spread sheet along with data about nuts harvested from other trees, producing a full and accurate record of the year’s crop.

The harvested nuts are stored in a sealed plastic bag containing moistened sphagnum moss. The bag is labeled to identify the parent tree and source of pollen. The bag is stored in a refrigerator at a temperature just above 32 degrees Fahrenheit to give the nuts the required cold treatment over winter. The temperature will keep the nuts dormant until sprouting starts in the spring just prior to planting time.

When ready, the nuts will be taken from storage and planted in what will be an orchard of hybrid chestnut trees. After four year’s of growth, the trees will be tested for blight resistance and strong American chestnut characteristics. Trees that meet those criteria will be selected for further back breeding to produce another generation of trees, all in an effort to develop blight resistant 94% American/6% Chinese trees that eventually can be set out in the Eastern forests.