Homeowners often hear conflicting information about what kind of pruning can be performed at what time of the year. Part of the confusion is related to the pruning of live oaks and red oaks because of the risk of oak wilt transmission, which will be specifically addressed in the next blog.
Pruning can be broadly divided into two kinds, removal of dead branches and removal of green branches. Pruning dead tissue out of a tree (often referred to in the industry as “deadwooding”), regardless of species, when cuts are done correctly at the branch collar by an ISA certified arborist, is fine to do year round as the cut is brought back to non conductive tissue where it won’t negatively affect the health of the tree. Infact, removing dead wood from about 2″ in diameter and larger is greatly beneficial as the tree can avoid using it’s resources trying to grow callous wood to absciss the dead branch on its own.
Pruning green tissue on a tree is more complex and different factors need to be kept into consideration, mainly the age of the tree and the amount of green branches that need to be removed. Also the species and the condition of the tree are important factors but for the sake of making this blog clear and concise we have to speak in general terms, so consulting with an arborist is often necessary. Mature trees are fairly intolerant to having green tissue removed and there should always be a reason to prune in the first place, whether to reduce or remove a hazardous limb, remove a rubbing branch or to clear the canopy for structures, roadways and driveways. If the amount of branches is moderate this can be done year round, if more extensive work is needed it is best to do it when the tree’s vascular system is at it’s slowest. This happens when outdoor temperatures are at extremes, when any part of the day is in the low nineties and above or below the mid forties, typically our summers and short lived winters. Pruning at these times of the year greatly reduces negative impact on the tree and avoids excessive stimulation of epicormic sprouts. The same temperature parameters apply to to young trees but larger amounts of green tissue can be removed in one growing season without damaging the tree’s health, making it an ideal age for pruning for good structure thus avoiding future problems and being forced to remove larger amounts of green as the tree matures.
I would like to reiterate that these are general guidelines and each individual tree needs to be examined carefully before deciding what kind of pruning needs to be performed and when to do it. Don’t hesitate to call your arborist for advice.
Mistletoe is a hemi-parasitic plant in the order Santalales that lives within the branches of a tree. Many different species of tree host mistletoe, here in central Texas it is most commonly found in cedar elms, hackberries, mesquite and red oaks. It often goes unnoticed by homeowners as the mistletoe leaves can be confused with those of the host tree but, as all our local host trees are deciduous and the mistletoe is evergreen, it is very easy to spot in the winter months.
Mistletoe seeds are mostly spread by bird excrement. Once the seed is deposited on the branch the mistletoe will start using the host tree for water and minerals severely depleting the hosts resources. Damage is also done to the branch structure of the host tree, accelerating decay and weakening the wood, which eventually can lead to branch failure.
There is no known solution to eradicating mistletoe from trees once the infection begins but the damage can be drastically reduced by having it periodically removed by your ISA certified arborist as maintenance pruning is being performed in the host tree. The mistletoe will resume sprouting usually within a year but its development has been greatly reduced much to the benefit of the infected tree.
Mulching is one of the biggest improvements in the health of a tree that a homeowner can make. It is also cheap and, if proper guidelines are followed, can be done without the help and oversight of an arborist.
One of the main benefits of mulch is the introduction of organic material in the soil. As I mentioned in my previous blog, urban trees are often starved of nutrients as we tend to remove all decomposing material from the surface of the soil to maintain a tidy look to our yards. In a forest, decomposing materials leech nitrogen, potassium and other valuable nutrients to the roots of the tree. Mulch makes up for these deficiencies in the urban landscape. Other benefits include improved water retention which is especially important for newly planted trees. It also helps keep competing grasses and weeds away from the roots which also benefit from the insulation the mulch offers, in other words it helps keep the soil temperature more stable, which in urban and suburban areas is often a problem.
Mulching though, is a benefit to the tree only if applied properly. When done incorrectly it can seriously harm the tree so guidelines need to be followed. Mulch needs to be spread between 2″ to 4″ deep at most making sure that none of it comes into contact with the trunk of the tree as this could trap moisture around the wood and become an entry point for decay. If practical it should be applied to at least the dripline of the tree but when possible even further as roots usually spread far past the canopy above.
Any kind of organic hardwood mulch will do the job. You can buy it by the bag from your nursery, get it delivered by the yard from specific companies or ask your arborist to keep the mulch generated from the chippings of your pruning job.
Illustrations courtesy of the International Society of Arboriculture
In this first blog I want to address some of the most common and generic issues that trees face in an urban environment. Trees in an urban landscape face many problems that are not present in their natural habitat, the forest. These issues will be tackled in greater detail in future blogs.
The roots that inhabit an urban soil lack an adequate amount of oxygen, bacteria, fungi and other organisms that are essential to the health of the tree. Urban soil has been described as “A soil material having a non-agricultural, manmade surface layer more than 50cm thick, that has been produced by mixing, filling, or by contamination of land surfaces in urban and suburban areas” (Bockheim,1974).
On the surface trees often have to compete for water and nutrients with turfgrass. A difficult coexistence that doesn’t occur in the trees natural habitat. This can be partially mitigated by mulching correctly, which will be the subject of the next blog.
Above ground trees tend to grow into unnatural shapes due to excessive light stimulus from lack of competition from other trees. They will have a tendency to grow multiple trunks and very large lateral branches that eventually become too heavy for the wood to support. This is not only a concern for the health of the tree, as large tears along the trunk will become an entry point of decay and compromise the structure of the rest of the tree, but is also a hazard to people and property. To correct this structural and subordination pruning can be done when the tree is young to prevent bad structure from occuring in the first place. In mature trees the hazard can be partially reduced by weight and sail reduction pruning and, as a last resort, an ANSI approved cabling system.