While trees look inactive going into winter, the fact is they continue to regulate their metabolism and only slow down some physiological activities. This decrease in photosynthesis and transpiration begins a tree’s dormant phase. Even during winter, trees continue to slowly grow roots, respire and take in water and nutrients.
A dormant tree needs to be protected to remain healthy and free from diseases and insects. Winter weather encourages destructive pests to snuggle in and wait for spring to revive their lifecycles. Here are a few things to keep in mind when preparing your trees for winter weather:
The first questions are “when should I prune?” and “how much should be pruned?” Branches touching the ground or those that are structurally weak should be removed before they are loaded with snow. A proper pruning cut made any time of year is almost always easier for a tree to recover from than a storm-damaged limb. Dead or diseased branches of any species of tree can be pruned at any time of year.
Otherwise, with only a few exceptions, most trees should be pruned during the dormant season. Conifers that are pruned while dormant will produce a little less sap and thus will attract fewer damaging insects such as bark beetles.
With deciduous fruit trees, wait until just before the spring growth flush to prune. This way, pruning wounds close more rapidly and may discourage some diseases and decay organisms from entering the cut.
As for how much pruning should be done, never remove more than 25 percent of a tree’s canopy in a single pruning event.
Mulch and aerate
Mulching and aerating the soil around a tree will help keep it healthy through the winter. A thin layer of mulch, 2 to 3 inches deep and at least 6 feet from the trunk, is recommended. This layer can reduce upper soil temperature by 40 degrees in summer and provides a protective blanket for winter.
Composted organic mulch works best on the surface, however, any biomass such as leaves, needles or chips will work. Even gravel is better than mineral soil. In addition to protecting feeder roots, mulch recycles nutrients and helps aerate the soil. The mulch layer also helps the tree capture rain water and it slows soil erosion.
Fertilize and water
With a well-established mulch layer, feeding indigenous (native) trees is not necessary. If the essential elements are in short supply, apply fertilizer evenly over the mulch. Be sure to use nitrogen lightly to avoid a vegetative “flush” of growth during late fall periods of warming. Stick with low numbers such as 8-2-4 or 4-4-4, slow-release fertilizers.
Watering, over or under, creates the majority of problems in landscapes. Trees like to have 30-day cycles of deep watering. Up to 85 percent of the absorbing roots are in the upper 2 feet of soil.
Dry spells, even in winter, can desiccate a tree very quickly. Use a dripper hose and monitor it carefully.
For more information on the care of trees visit: www.treesaregood.org.