Contents
Miscellaneous Questions
In the fall a lot of the needles on my pine tree turn yellow. What is going on?
Is it a problem for trees to be budded out in the middle of winter?
Pruning Questions
When is the best time of year to prune a tree?
What does a good pruning cut look like?
Where should a pruning cut be made?
What are some guidelines for pruning a tree as it grows?
Should I use pruning seal?
MISCELLANEOUS QUESTIONS
In the fall a lot of the needles on my pine tree turn yellow. What is going on?
If the needles on the outside eight inches or so of the branches are still green and healthy-looking there is probably not a problem. Pines shed older, interior needles every year, although some years they hang onto more of the needles, with a larger needle shed the following year.
However, if needles at the tips of the branches are yellow or abnormal-looking, there probably is a problem, such as tip moth damage or drought. If this is the case, consult your extension office for help in diagnosing the responding to the problem.
Is it a problem for trees to be budded out in the middle of winter?
Oftentimes, when we experience mild conditions in the middle of winter, home gardeners become concerned that their trees will break dormancy too soon. Then the gardeners look at their trees and notice that the trees have buds on them. However, if they had looked at the same trees in late summer they would have noticed the buds then, too.
Leaf and twig buds are produced the previous year. Depending on the tree or shrub species, flower buds may also be produced the previous year. So the presence of buds does not indicate that there is a problem
That does not mean the weather will not deal us a blow, as it does occasionally, when unusually cold weather late in the spring dashes our hopes of an apple crop by freezing buds or flowers.
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PRUNING QUESTIONS
When is the best time of year to prune a tree?
Late winter is the best time to prune most trees. At this time the trees are still dormant, but will soon break dormancy and begun new spring growth; so pruning cuts will seal over quickly, minimizing risks of decay.
Maples, birches and walnuts tend to have a lot of sap flow when they are pruned in late winter. This is not considered harmful to the tree, but to minimize sap flow these trees can be pruned in January.
In the case of pines, pruning is recommended in June or July in Nebraska, after new candles (new needle bearing twigs) are at least half grown.
Avoid pruning in September and October. Branches pruned at this time may be more prone to infection.
Avoid pruning during the rapid growth stage in spring, especially April and May. Bark is tender and tears easily at this time.
What does a good pruning cut look like?
If you look at a pruning cut a year later, you should see callus formation in roughly an even ring, something like a skinny donut. As time passes, the ring should grow larger until eventually it may cover the cut, especially when a young, actively growing tree is pruned.
Ideally, branches will be pruned out before they are two inches in diameter, with cuts made properly.
Where should a pruning cut be made?
On the upper side of the branch attachment there will be a ridge of bark, and on the lower side of the branch, a swollen area called the branch collar. Make a diagonal cut from just outside the bark ridge on top, to just outside the branch collar below.
Some branches do not have a branch bark ridge, but may have what looks like a seam, instead, where bark appears to be shoved into the union. This is referred to as “included bark.” Make a diagonal pruning cut from the included bark on top, to just outside the branch collar on the lower side of the branch.
What are some guidelines for pruning a tree as it grows?
At planting time remove only broken or diseases branches.
In general, avoid unnecessary pruning for the first two to three years, to allow the tree to overcome transplant shock.
After that, prune, as needed, each year, to develop a good tree form and remove branches potential problems.
Gradually raise the height of the tree, as needed, to allow clearance for mowing, and to ensure that the tree will not obstruct foot or vehicle traffic or violate clearance laws. Ideally, necessary removal will be done before the branch reaches two inches in diameter.
As form is developed, you will need to make decisions regarding which branches to leave and which to prune out. Target branches that show signs of weak attachment, as indicated below:
- Narrow branch angles.
- Included branch, as evidenced by what appears to be a seam of bark pressed into the tree at the area of branch attachment.
- A crack extending below the point of branch attachment, especially where there is also included bark.
Co-dominant stems: Unless a tree is of a species with a natural multi-stem habit, it should have only one leader. Two stems growing together may push against one another as they grow, creating a situation in which the tree splits during a storm. To prevent that, one of the stems should be removed when the tree is young.
Some trees, such as lindens or Bradford pear, tend to have a lot of branches with included bark. If you attempted to remove all the branches with included bark you may have nothing left. On these trees, base decisions also on the other signs of weak branch attachment.
Hackberry trees are native to Nebraska and are reliable trees. However, they need to be pruned as they grow, to remove branches with included bark, which may fail during winter storms.
Pruning Trees by Dave Mooter, Nebraska Forest Service
and Pruning Trees and Shrubs, Iowa State University.
Should I use pruning seal?
No. Pruning seals do not promote tree health, and may actually promote decay.
Recent research shows that if pruning is done during dry, hot periods of summer, it may help to wrap the pruned area with white plastic sheeting temporarily. The sheeting prevents rapid drying during the initial callus formation period. Apply the sheeting within a few minutes after cutting off the branch, and secure it with tape. Remove it two to three weeks later. For more information, see
Pruning Landscape Trees: An Overview, from Utah State University.
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