Monday, November 11, 2013

Container grown pecan trees: Fall planting and overwintering potted trees

   For the past three weekends, I've been planting the pecan seedlings I started in containers this past spring. Fall is the perfect time for planting container grown trees (photo at right).  For the most part, the soil has just enough moisture to make digging the planting hole easy but is dry enough to allow you to back fill the planting hole with loose, friable soil. Fall planting also allows the roots of the young tree to begin growing out into the surrounding soil almost immediately, helping to decrease transplant shock.
      The trees I planted this fall averaged about 10 to 12 inches in height with an air-pruned root system only about 4 1/2 inches deep (photo at left).  The depth of the root system makes it very easy to transplant--one shovel full of soil and I've got a hole deep enough for the tree. I like to to plant these trees about an inch deeper than they had grown in the container, allowing the root ball to be fully covered with soil. Planting deep ensures that the soil-less media that still surrounds the root system is not directly exposed to drying winds and the tree doesn't desiccate.
     The photo at right gives you a good look at the type of root system that develops inside the bottomless container. The tap root has been air-pruned forcing the development of  a network of fine lateral roots. Once this tree is planted in the field, the air-pruned taproot will re-sprout often creating two or three new "taproots". Next year, my transplanted seedlings will put on just a few inches of new top growth but more importantly, they will be developing massive root systems designed by nature to ensure tree survival.
     I planted about 150 trees this fall but still had some trees left over. With winter's first blast of arctic air forecast for this week, I took some steps to protect my remaining potted trees from the big chill. Although pecan trunks and branches can stand temperatures down to -26 F, the roots of pecan trees will freeze at about +19 F.  This means I needed to take some steps to protect the roots of my remaining potted trees.
    I moved the trees from the nursery bench into my vegetable garden. The garden has two things that makes in perfect for overwintering trees. First, we have raised beds in the garden and the garden paths are just the perfect width for a flat of trees. With a raised bed on either side of the flat, it looks like the trees are partially buried in the soil (photo above).  The garden is also surrounded by a fence that will keep the trees safe from mid-winter rabbit feeding.
    To prevent root freezing, I used a thick carpet of hay packed around the tree flats to insulate and trap the soil's heat around the trees (photo below).