Winter Tree Care
Did you know that winter is a good time to prune and care for deciduous trees? Advantages of winter tree pruning include the unobstructed visibility by leaves of damaged limbs that need pruning or removal, structural pruning to improve future tree development, decreased presence and activity of disease and insects, and potential for savings on the cost of the tree work due to reduced workloads.
During the winter dormant season, after the leaves have fallen off a deciduous tree, it is easier for an arborist to inspect a tree for damaged limbs. Broken or decayed limbs, and detached limbs stuck in the tree canopy, commonly referred to as hangers, should be removed as part of recommended pruning. The arborist can also inspect the structure of the tree and branches, and may recommend pruning to improve airflow through the tree, which may help prevent storm damage during normal weather-related events. However, preventative structural pruning cannot protect a tree from damage as a result of a derecho, tornado, other straight-line wind events, or ice and snow loads that occur during extreme weather conditions. Trees that sustain damage because of these types of storm events are more likely to suffer from future insect and disease infestations if corrective pruning is not performed.
An arborist can readily identify signs of disease presence, such as fruiting structures or insect infestations such as boreholes in the tree without the obstruction of leaves. Dormant pruning in the winter will permit callous tissue to begin sealing the pruning cut before insects and disease organisms become active as the weather warms in the spring. Insects that carry harmful tree diseases such as Oak Wilt or Dutch Elm Disease are less active during the cold winter weather. Trees that are pruned during the warmer months of the year can be more susceptible to disease and insect damage due to increased pest activity, and the resulting tree sap on freshly cut limbs and branches can attract insects such as borers and sap beetles; sap flow in the tree is slowed during the colder dormant season. Trees in the rosacea family such as apple, pear, shadbush, and hawthorn should also be pruned during the dormant season to reduce the spread of bacterial fire blight disease, as the transmission is slowed during the cold winter months.
What should be done to protect newly planted tree trunks from wildlife during the winter? Buck deer rub their antlers on young trees to remove the velvet, thus marking their territory. This rutting activity occurs during the late fall and early winter. The antler rubbing damages the cambium layer of the tree, and its removal can lead to the death of the tree or allow insects and diseases to enter the trunk. Deer will also eat, or “browse,” on tender tree buds and twigs when food is scarce during the winter. Mice and other small rodents chew on tree trunks when there is little other food available, which can also have detrimental effects on young trees.
There are several types of protection products available that can be installed on newly planted trees. One method is to wrap the tree trunks with tree wrap paper to protect the young trunks from browsing animals. Another effective method includes installing wire mesh fastened with zip ties or ridged plastic protectors around the tree trunk to protect trunks from deer rutting (see link below). The supplies used to protect tree trunks can be purchased at local nurseries or hardware stores. If several trees need protection, tall fencing, over 6 feet tall can be installed around the entire group of trees or property if deer populations are high.
In the State of Maryland, arborists that conduct tree assessments, tree care, maintenance, and removals, must be a Maryland Licensed Tree Expert. The Maryland Department of Natural Resources regulates companies that perform tree work. To locate a Maryland Licensed Tree Expert, visit https://dnrweb.dnr.state.md.us/forests/tree_expert_search.asp. The list includes companies that have Maryland Licensed Tree Experts on their staff.
If the Tree Expert recommends pruning more than 20% of live wood on a tree 36 inches in circumference measured at 4.5 feet above the ground, the City of College Park requires a property owner to obtain a permit to complete this work per Ordinance 21-O-09. Complete the application to begin the free permitting process. The application to prune or remove trees is found on the City of College Park webpage, Guide to Trees at www.collegeparkmd.gov/Trees. The webpage contains other useful information about how residents can care for their trees.
From the City's Tree and Landscape Board