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ISSUE 11   JULY 15, 1999

 

TREES

Transplant Shock

    Whether grown in a nursery, or from the wild, trees which are planted are actually transplanted. Since
roots are severed and trees enter new environments, there will always be stress associated with
transplanting. This stress can lead to shock, which is usually noticed only when trees look weak or begin
to decline. Oftentimes, it’s too late to save the trees. Common symptoms of transplant shock in broadleaf
trees include leaf wilting or rolling and browning of leaf margins, while conifers show an overall gray-green
discoloration of foliage and tip dieback of needles. All trees, with transplant shock, show reduced growth
and may have sprouts developing from the trunk and off the sides of large limbs. If shock is severe, twigs,
limbs, and possibly entire trees, can die back.

    Two common causes of transplant failure are transplanting too large of a tree with too small of a soil
ball and improper watering. Generally, the soil ball should be a minimum of 12 inches for each 1 inch of
tree trunk diameter. Trees which are more transplant tolerant may survive transplanting with smaller soil
balls.

    Too much or too little water after transplanting are major causes of tree loss. The site should be
thoroughly watered immediately after planting. Thereafter, the soil must be regularly monitored to prevent
drying out. If rainfall is inadequate, the soil around the tree’s roots should be deeply watered approximately
ever 10-14 days. When unsure if the soil is drying, dig down 3 to 4 inches next to the plant. Wet soil at that
depth verifies watering is not needed at that time.

    The best cure for transplant shock is prevention. Before transplanting a tree or shrub, consider transplant
tolerance of the tree species, condition of the tree, season to transplant, new planting site conditions, the
equipment needed, and follow-up care. All of these topics are covered in detail in NDSU Extension
publication F-1147 "Transplanting Trees and Shrubs."

    Once a tree shows symptoms of transplant shock, preventing further damage may be difficult. Proper
watering, fertilization, and pruning can help a tree pull through tough times. Only fertilize trees before July 1
or after the leaves drop in the fall. Late summer and early fall fertilization can lead to juvenile growth which
may not harden off before fall freeze-up. Any stems that die back should be removed along with any suckers
that develop on the trunks of trees and off the sides of large limbs. Suckers grow rapidly, but are weakly
attached and utilize energy which should be used in young shoots developing from branch tips. Before
replacing trees, which die after transplanting, correct the problem(s) or choose tree species which are more
tolerant to the site. Keep in mind that smaller trees of a particular species typically transplant better and catch
up in growth to larger trees of the same species.

Venturia Shoot Blight of Aspen and Poplars

    If you believe that you’ve seen fire blight on aspen or other poplars lately, you’re not alone. It’s not
fire blight, but a shoot blight caused by a Venturia sp. fungus. This disease causes "shepherd’s crooks"
similar to those caused by fire blight on apples, pears, mountain-ash and many other plants in the Rose family.
Unlike fire blight, Venturia shoot blight of aspen has little or no economic significance. Trees which are more
than 15 feet tall show negligible damage, while smaller trees are occasionally threatened by this disease.
This follows with the fungus’ purpose in nature...to help thin out aspen stands as they mature. As with
many of the tree problems we have seen this year, Venturia shoot blight is favored by wet weather. While
the shepherd’s crooks are caused by early season infections, late season infections should only result in
leaf spots.

    Occasionally, management options are desired in landscape settings. Blighted twigs may be removed
well below the margin that occurs between healthy and infected tissue. Also, leaves should be raked up
around landscape plantings in the fall. Fungicide treatments are seldom necessary.

Marcus Jackson
Extension Forester


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