Frequently Asked Pruning Questions
1. What is pruning?
Pruning is the cutting and removal of branches, twigs and other parts of trees (PAUSE). Pruning is not neccessarily for improving plant health. First and foremost, pruning is the removal of parts of trees, shrubs or plants. Pruning is commonly performed to promote plant health or improve branch structure. But many times, pruning is done for other reasons such as:
a. Art - like topiary (shaping foliage in clusters, geometric shapes or like animal forms).
b. To clear a visual corridor for a scenic view near a house.
c. Crown (canopy) reduction to reduce the height of trees under power lines.
Those all demonstrate that the purpose of pruning is generally to manipulate and maintain control of plants.
Pruning is done for corrective measures, plant health, aesthetics, vegetation control and art.
The method in which plant parts are removed may determine whether the practice is "PRUNING" or "CUTTING". Proper pruning (in the eyes of a professional like an arborist) will remove foliage while doing little harm to a plant. Removal of tree branches or plant parts that substantially causes damage or decline should be referred to as "cutting" (not as "pruning").
2. When is the best time of year for pruning.
The best time of year can vary from tree to tree and plant to plant. Exceptions can be discussed individually.
Information from a book titled A NEW TREE BIOLOGY by Dr. Alex Shigo is a reference that simplifies this matter of "when to prune."
Page 442 of that book encourages to do pruning in the dormant season or after leaves have matured. Page 442 says to TRY to avoid pruning when leaves are forming and when leaves are falling. That page also states "You can prune any time."
Important keys from that book are "TRY" and "ANY TIME".
In general, moderate pruning can be done throughout the entire year. During a year, we can choose our level of "perfection" for pruning. "IF" we can avoid pruning while leaves are forming; great. "IF" not, that may be the best we can do, and the plants should develop reasonably well.
This image helps to show why "NEED" can exceed "RULES" The large limb that ripped off this pine should have been removed before it broke (8 years before this image date would have been better). Suppose you had this tree, or one like it. And suppose the time is late September. Why would you wait for winter pruning when the "NEED" to remove a weak limb like this exists?
In many cases, if proper pruning has been skipped or neglected, the time to prune may be NOW. If the weak limb was pruned off this pine in summer to fall, the 7" pruning cut would pale in comparison to this kind of damage.
3. How much of a plant can be removed?
As a general rule - an arborist's rule - don't remove more than one-fourth (1/4) of a tree's leaf-bearing canopy. So don't prune away more than 25% of the tree at one time.
If trees are mature or old, less material should be removed. On older trees, don't remove more than about 10% to 20% of the leaf-bearing canopy. The older the tree, the less that should be removed at one time.
With fruit trees, this may be different. Once a fruit tree like apple or pear reaches the desired size, prune back as much you need to bring the canopy back to last year's size (the circumference or perimeter of the canopy).
Pollarding is when all the sprouts are removed from a tree - entirely - every year, leaving "fist-like" knobs - the pollard heads. Every year, every sprout must be removed without cutting into the knobs. The knobs will become slightly larger each year. The basic frame-work of the tree will, or can, remain the same size from year to year.
4. Should pruning wounds be sealed or painted?
No (with an exception).
Research has discovered and demonstrated that pruning wound sealers - or tree paint - generally causes damage to trees by promoting decay.
The once-accepted idea that wound sealers were beneficial was originally taught without researching the internal portion of trees properly. The old-school belief was based on external evidence that wounds closed faster (The wounds closed faster, but the decay went much deeper).
Trees and many shrubs make their own natural and internal wound dressing - they compartmentalize and isolate or "wall-off" the area of decay near a wound or pruning cut.
One EXCEPTION can be OAK trees where "Oak Wilt" disease is known to be a serious problem. In regions with a significant oak wilt problem, some professionals will coat pruning cuts made in winter and spring. There is no need to apply thick glossy layers. A thin coat or dressing can suffice.
5. Do trees or plants "heal" after pruning?
No, not really. They do not heal. The plants "compartmentalize" the cut or wound area by encasing it with new tissue that eventually should close-over and seal-in the pruning cut.
6. What is topping?
Topping is indiscriminate cutting or "butchery" of tree branches or leaders. It is a stubbing-back that leaves bare limbs or leaders, or, leaves lateral limbs that are not big enough for taking over as the leaders or tree top. One nickname for topping is "hat-racking".
Topping is probably the most harmful tree "cutting" practice. Often, people top trees because they believe it will make trees less hazardous. The opposite is true. Topping usually makes trees more hazardous as well as unhealthy. Topping promotes decay.
Be aware that with shrubs, "rules may be broken." Sometimes shrubs are allowed to get too big and may be renovated by topping. The fact that shrubs are small eliminates the same hazards that are caused by topping trees. This does not mean that topping is healthy for shrubs. It just means that people may choose to top and renovate a shrub rather than remove it.
7. If a tree located next door and overhangs my property, can I cut the branches?
Yes (part of it).
The general rule of thumb (explained in a book called ARBORICULTURE AND THE LAW) is that the property line starts at ground level and extends vertically upward for "infinity" as far as our purpose is concerned.
The branches may be removed, legally, without crossing the property line.
There may be a few USA cities (such as in New York state at some point in time) where the neighbors who own the overhanging trees may demand to keep the branches or debris that is cut off. But that would not prevent us from removing the overhanging limbs.
Also, in a few rare cases, a neighbor might have some "say" about trees on a property next door. An example might be that two homeowners invested money to purchase trees for a hedge row. But that's an exception, not the rule.
When removing branches overhanging from trees next door, it's advisable to be wise about communicating and negotiating. And be certain about the exact location of the property line. A fence might not be located on a property line.
M.D. Vaden M. D. Vaden Beaverton, Oregon | Portland Landscape & Tree