While the normal winter low for this region of Kentucky is in the 0-5oF range, the low temperature in several of the winters since 1978 have fallen to the -20 to -25 F range. In these very cold winters there was no damage on established trees in either the Wilmoth grove or ours, with the exception of Persian walnuts, which suffered twig dieback and some bark splitting, but which nevertheless survived and completely recovered.
Nut trees that have been encouraged to grow late in the season and have not had adequate time to harden off before moderate freezing occurs, can sometimes be damaged in the fall with a sudden onset of very cold weather. This damage is usually limited to Persian walnuts and very small, perhaps stressed trees of other species.
Winter damage of any kind has never been observed on rootstock trees at either the Nolin River or the Wilmoth Nursery. This includes seedlings of black walnut, northern pecan, chestnut, and persimmon. Based on our observations, we believe that our stock is generally hardy to at least -25o F. Some species such as shagbark hickory, black walnut, butternut, and most heartnuts are probably hardy at lower temperatures unless they are growing under moisture stress during the summer.
Establishing grafted nut trees is not difficult, given a good site and some minimum essential care. A good site requires a soil that is deep and well-drained. While all nut trees can handle periodic flooding, they don't grow well in ground where they will have "wet feet" for a considerable period of the year. Pecans and persimmons exhibit good growth over a wide range of pH values, from an acid 5.8 to alkaline 7.5. Generally walnuts prefer the sweeter, or more alkaline soils, and chestnuts thrive under very acid condition and pH in the range of 6 to 7 is ideal.
Fertilization is not normally a part of first-year establishment. However, we would recommend using topsoil to backfill around the roots, and mulching heavily with compost, well-rotted manure, or other organic mulch after filling the hole. This will help to supply the numerous trace minerals required by nut trees. The mulch will have the added benefits of suppression of weed growth and conservation of soil moisture.
Most important to establishing new transplants is weekly or bi-weekly watering. This is essential during dry spells. While the young transplant does some growing above ground, most of the important growth is in the root zone, as the tree reestablishes itself in the soil. Two inches of weekly rain is usually sufficient. Deficiencies should be corrected by watering up to three or four inches a week during dry spells. Extra large trees may require 10 gallons or more of water each week during the first growing season in the event of drought.
Thus, the three important factors to consider in planting (1) site; well-drained, deep soil, proper pH level, fertile soil (2) watering; weekly or bi-weekly, 2-4 inches; (3) mulching; weed suppressions, moisture conservation, micronutrient supply.
The year after the trees are established, begin fertilizing. Nut trees can be very heavy nitrogen feeders, similar to corn, and it is under good fertility levels that the trees make their most vigorous growth and produce their best crops of nuts. Fertilize in late winter to mid-spring. Later applications run the risk of forcing late season growth that may be winter killed.
All trees will be on 2- to 6-year-old root stock. All walnut species (Juglans) are grafted on black walnut rootstock. All pecan (Carya) species are grafted on northern pecan rootstock. Chestnuts are grafted on closely related chestnut seedlings, persimmons are grafted on American persimmon seedlings, and pawpaws on pawpaw seedlings.
The majority of nut trees are strongly tap rooted. To preserve as much of the root as possible, we hire professional backhoe operators when digging our trees.